Bristol Astrophysics Journal Club Introduction
Term dates 2010-2011 are
Dates for 2010/2011
* Autumn Term
4 October - 17 December
* Spring Term
14 January - 1 April
* Summer Term
3 May - 24 June
Bank holidays in 2011 on a Monday
Monday 2 May (bank holiday)
Monday 30 May (bank holiday)
| Date | Speaker | Title | Authors | Reference |
|---|---|---|---|---|
| 8/11/2010 | Rhys Morris | The distance to the Andromeda Galaxy from eclipsing binaries | F. Vilardell et al. | astro-ph/0911.3391 |
| " | Avon Huxor | Our Milky Way as a Pure-Disk Galaxy -- A Challenge for Galaxy Formation | Juntai Shen | astro-ph/1005.0385v2 |
| 22/11/2010 | Elizabeth Stanway | Detailed Radio View on Two Stellar Explosions and Their Host Galaxy: XRF080109/SN2008D and SN2007uy in NGC2770 | A.J. van der Horst et al. | astro-ph/1011.2521 |
| " | Liz Mannering | The Sudden Death of the Nearest Quasar | Schawinski et al. | 2010ApJ...724L..30S |
| 6/12/2010 | Paul Giles | Dust Attenuation in UV-selected Starbursts at High Redshift and their Local Counterparts: Implications for the Cosmic Star Formation Rate Density | Overzier et al. | astro-ph/1011.6098 |
| " | Kian Momtahan | Dark matter awareness week presentation |
| Date | Speaker | Title | Authors | Reference |
|---|---|---|---|---|
| 24/1/2011 | Postponed | |||
| " | ||||
| 7/2/2011 | Poemwai Chainakun | Statistical comparison of clouds and star clusters | O. Lomax, A. P. Whitworth, A. Cartwright | Astro-ph/1010.5944v2 |
| " | Valentina Squitieri | On the Deflection of a Light Ray from its Rectilinear Motion | Johann Georg von Soldner | wikisource |
| 28/2/2011 | Swapan Das | BIG FISH, SMALL FISH: TWO NEW ULTRA-FAINT SATELLITES OF THE MILKY WAY | Belokurov et al. | astro-ph/1002.0504 |
| " | Ged (Ben) Kitchener | DIRECT IMAGING OF FINE STRUCTURES IN GIANT PLANET-FORMING REGIONS OF THE PROTOPLANETARY DISK AROUND AB AURIGAE | J. Hashimoto et al | ApJl |
| 7/3/2011 | Alex Lockey | Anisotropic Metal-enriched Outflows Driven by AGN in Clusters of Galaxies | C. C. Kirkpatrick, B. R. McNamara, K. W. Cavagnolo | astro-ph/1103.0793 |
| " | Rhys Morris | PHR1315-6555: a bipolar planetary nebula in the compact Hyades-age open cluster ESO96-SC04 | Quentin A. Parker et al. | astro-ph/1101.3814 |
| 21/3/2011 | Valentina Squitieri | Error estimation in astronomy: A guide | Rene Andrae | Astro-ph/1009.2755 |
| " | Liz Mannering | " | " | " |
| Date | Speaker | Title | Authors | Reference |
|---|---|---|---|---|
| 9/5/2011 | Paul Giles | A merger mystery: no radio halo in the merging cluster Abell 2146 | H.R. Russell et al. | astro-ph/1105.0435 |
| " | ||||
| 23/5/2011 | Kian Momtahan | The Spitzer discovery of a galaxy with infrared emission solely due to AGN activity | S. Hony et al. | astro-ph/1105.2492 |
| " | Alex Lockey | Early UV Ingress in WASP-12b: Measuring Planetary Magnetic Fields | A. A. Vidotto, M. Jardine, Ch. Helling | astro-ph/1009.5947 |
| 6/6/2011 | Swapan Das | |||
| " | Ged (Ben) Kitchener | Small Bites: Star formation recipes in extreme dwarfs | Sambit Roychowdhury | astro-ph/1103.6117 |
| 10/6/2011 | ||||
| " |
Error estimation in astronomy: A guide
Rene Andrae
Abstract: Estimating errors is a crucial part of any scientific
analysis. Whenever a parameter is estimated (model-based or not),
an error estimate is necessary. Any parameter estimate that is
given without an error estimate is meaningless. Nevertheless, many
(undergraduate or graduate) students have to teach such methods
for error estimation to themselves when working scientifically for
the first time. This manuscript presents an easy-to-understand
overview of different methods for error estimation that are
applicable to both model-based and model-independent parameter
estimates. These methods are not discussed in detail, but their
basics are briefly outlined and their assumptions carefully
noted. In particular, the methods for error estimation discussed
are grid search, varying $\chi^2$, the Fisher matrix, Monte-Carlo
methods, error propagation, data resampling, and
bootstrapping. Finally, a method is outlined how to propagate
measurement errors through complex data-reduction pipelines.
http://arxiv.org/abs/1009.2755
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Paper: astro-ph/0403327
replaced with revised version Fri, 19 Mar 2004 17:52:20 GMT (37kb)
Title: Have we detected one of the sources responsible for an early
reionisation of the Universe?
Authors: Massimo Ricotti, Martin G. Haehnelt, Max Pettini and Martin
J. Rees
Comments: 6 pages including 4 figures. Submitted to MNRAS
letters. Revised version with correction to the inferred space density
of sources
http://arXiv.org/abs/astro-ph/0403327 , 37kb)
\
Paper (*cross-listing*): hep-ph/0307266
replaced with revised version Mon, 29 Mar 2004 14:29:43 GMT (61kb)
Title: Homestake result, sterile neutrinos and low energy solar
neutrino
experiments
Authors: P. C. de Holanda and A. Yu. Smirnov
Comments: Figures 5 and 6 modified, shorter version will be published
in PRD
\\ ( http://arXiv.org/abs/hep-ph/0307266 , 61kb)
Period-luminosity relations for Galactic Cepheid variables with
independent distance measurements
Chow-Choong Ngeow, Shashi M. Kanbur
Monthly Notices of the Royal Astronomical Society; Volume 349, Issue
3,
Page 1130
http://www.blackwell-synergy.com/links/doi/10.1111/j.1365-2966.2004.07595.x
Title: Cepheid distances from infrared long-baseline interferometry -
II. Calibration of the Period-Radius and Period-Luminosity relations
Authors: P. Kervella, D. Bersier, D. Mourard, N. Nardetto, V. Coude du
Foresto
Comments: 7 pages, 3 figures, submitted to Astronomy & Astrophysics
Using our interferometric observations of seven classical Cepheids
reported in Kervella et al. (2003, Paper I), complemented by
previously existing measurements, we derive new calibrations of the
Cepheids Period-Radius (P-R) and Period-Luminosity (P-L) relations. We
obtain a P-R relation of log R = [0.767 +/- 0.009] log P + [1.091 +/-
0.011], only 1 sigma away from the relation obtained by Gieren et
al. (1998). We therefore confirm their P-R relation at a level of
Delta(log R) = +/- 0.02. We also derive an original calibration of the
P-L relation, assuming the slopes derived by Gieren et al. (1998)
from LMC Cepheids, alpha_K = -3.267 +/- 0.042 and alpha_V = -2.769 +/-
0.073. With a P-L relation of the form M = alpha (log P - 1) + beta,
we obtain log P = 1 reference points of beta(K) = -5.904 +/- 0.063 and
beta(V) = -4.209 +/- 0.075. Our calibration in the V band is
statistically identical to the geometrical result of Lanoix et
al. (1999).
\\ ( http://arXiv.org/abs/astro-ph/0404179 , 90kb)
Updated pulsation models for anomalous Cepheids:
M. Marconi, G. Fiorentino and F. Caputo
A&A 417 (2004) 1101-1114 (Section 'Stellar structure and evolution')
http://publish.edpsciences.org/abstract/aa/v417/p1101
Gamma-Ray Bursts are Produced Predominately in the Early Universe
J. R. Lin, S. N. Zhang, and T. P. Li
Page 819 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ17944
]
First Star Signature in Infrared Background Anisotropies
Asantha Cooray, James J. Bock, Brian Keatin, Andrew E. Lange, and
T. Matsumoto
Page 611 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ58833
]
Title: Discovery of a Transient U-band Dropout in a Lyman-Break
Survey: A Tidally-Disrupted Star at z = 3.3?
Authors: Daniel Stern (1), P.G. van Dokkum (2), Peter Nugent (3),
D.J. Sand (4), R.S. Ellis (4), Mark Sullivan (5), J.S. Bloom (6),
D.A. Frail (7), J.-P. Kneib (4,8), L.V.E. Koopmans (9), Tommaso Treu
(10) ((1) JPL/Caltech, (2) Yale University, (3) LBNL, (4) Caltech, (5)
University of Durham, (6) Harvard/CfA, (7) NRAO, (8) OMP, (9) Kapteyn
Astron. Inst., (10) UCLA)
Comments: 20 pages, 4 figures; to appear in the Astrophysical Journal;
desparately seeking archival images of Abell 267 from Summer 2001
We report the discovery of a transient source in the central regions
of galaxy cluster Abell 267. The object, which we call "PALS1", was
found in a survey aimed at identifying highly-magnified Lyman-break
galaxies in the fields of intervening rich clusters. At discovery, the
source had U>24.7 (2-sigma; AB), g=21.96, and very blue g-r and r-i
colors; i.e., PALS1 was a U-band drop-out, characteristic of
star-forming galaxies and quasars at z~3. However, three months later
the source had faded by more than three magnitudes. Further
observations showed a continued decline in luminosity, to R>26.4 seven
months after discovery. Though the apparent brightness is suggestive
of a supernova at roughly the cluster redshift, we show that the
photometry and light curve argue against any known type of supernova
at any redshift. The spectral energy distribution and location near
the center of a galaxy cluster are consistent with the hypothesis that
PALS1 is a gravitationally-lensed transient at z~3.3. If this
interpretation is correct, the source is magnified by a factor of 4-7
and two counterimages are predicted. Our lens model predicts time
delays between the three images of 1-10 years and that we have
witnessed the final occurrence of the transient. The intense
luminosity (M(AB) ~ -23.5 after correcting for lensing) and blue UV
continuum (implying T>50,000 K) argue the source may have been a flare
resulting from the tidal disruption of a star by a 10^6-10^8
solar-mass black hole. Regardless of its physical nature, PALS1
highlights the importance of monitoring regions of high magnification
in galaxy clusters for distant, time-varying phenomena.
\\ ( http://arXiv.org/abs/astro-ph/0405482 , 238kb)
Paper: astro-ph/0406022
Date: Tue, 1 Jun 2004 13:15:11 GMT (43kb)
Title: Confusion in the infrared: Spitzer and beyond
Authors: H. Dole, G. H. Rieke, G. Lagache, J-L. Puget,
A. Alonso-Herrero, L. Bai, M. Blaylock, E. Egami, C. W. Engelbracht,
K. D. Gordon, D. C. Hines, D. M. Kelly, E. Le Floc'h, K. A. Misselt,
J. E. Morrison, J. Muzerolle, C. Papovich, P. G. Perez-Gonzalez,
M. J. Rieke, J. R. Rigby, G. Neugebauer, J. A. Stansberry,
K. Y. L. Su, E. T. Young, C. A. Beichman, P. L. Richards
Comments: Accepted for Publication in ApJS Special Issue on Spitzer. 4
pages, 2 B&W figures. emulateapj. Also available at
http://ssc.spitzer.caltech.edu/pubs/journal2004.html
We use the source counts measured with the Multiband Imaging
Photometer for Spitzer (MIPS) at 24, 70, and 160 microns to determine
the 5-sigma confusion limits due to extragalactic sources: 56
micro-Jy, 3.2 and 40 mJy at 24, 70 and 160 microns, respectively. We
also make predictions for confusion limits for a number of proposed
far infrared missions of larger aperture (3.5 to 10m diameter).
\\ ( http://arXiv.org/abs/astro-ph/0406022 , 43kb)
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\\
Paper: astro-ph/0406056
Date: Wed, 2 Jun 2004 11:48:27 GMT (493kb)
Title: Discovery of optically faint obscured quasars with Virtual
Observatory
tools
Authors: P. Padovani (1), M. G. Allen (2), P. Rosati (3), N. A. Walton
(4) ((1)
ST-Ecf/ESO, (2) CDS, (3) ESO, (4) Ioa)
Comments: 16 pages, 6 figures, accepted for publication in Astronomy &
Astrophysics. PDF file with higher resolution figures available at
http://www.eso.org/~ppadovan/AVO-paper.pdf
We use Virtual Observatory (VO) tools to identify optically faint,
obscured (i.e., type 2) active galactic nuclei (AGN) in the two Great
Observatories Origins Deep Survey (GOODS) fields. By employing
publicly available X-ray and optical data and catalogues we discover
68 type 2 AGN candidates. The X-ray powers of these sources are
estimated by using a previously known correlation between X-ray
luminosity and X-ray-to-optical flux ratio. Thirty-one of our
candidates have high estimated powers (Lx > 10^44 erg/s) and therefore
qualify as optically obscured quasars, the so-called ``QSO 2''. Based
on the derived X-ray powers, our candidates are likely to be at
relatively high redshifts, z ~ 3, with the QSO 2 at z ~ 4. By going ~
3 magnitudes fainter than previously known type 2 AGN in the two GOODS
fields we are sampling a region of redshift - power space which was
previously unreachable with classical methods. Our method brings to 40
the number of QSO 2 in the GOODS fields, an improvement of a factor ~
4 when compared to the only 9 such sources previously known. We derive
a QSO 2 surface density down to 10^-15 erg/cm^2/s in the 0.5 - 8 keV
band of >~ 330/deg^2, ~ 30% of which is made up of previously known
sources. This is larger than current estimates and some predictions
and suggests that the surface density of QSO 2 at faint flux limits
has been underestimated. This work demonstrates that VO tools are
mature enough to produce cutting-edge science results by exploiting
astronomical data beyond ``classical'' identification limits (R <~ 25)
with interoperable tools for statistical identification of sources
using multiwavelength information.
\\ ( http://arXiv.org/abs/astro-ph/0406056 , 493kb)
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The Effect of Metallicity on Cepheid-based Distances
Shoko Sakai, Laura Ferrarese, Robert C. Kennicutt, Jr., and Abhijit
Saha
Page 42 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ59357 ]
Detecting Population III Stars through Observations of Near-Infrared
Cosmic Infrared Background Anisotropies
A. Kashlinsky, R. Arendt, Jonathan P. Gardner, John C. Mather, and
S. Harvey Moseley
Page 1 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ18028 ]
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\\
Paper: astro-ph/0308467
replaced with revised version Mon, 14 Jun 2004 13:46:31 GMT (592kb)
Title: The Size Distribution of Trans-Neptunian Bodies
Authors: G. M. Bernstein, D. E. Trilling, R. L. Allen, M. E. Brown,
M. Holman,
and R. Malhotra
Comments: Revised version accepted to the Astronomical
Journal. Numerical
results are very slightly revised. Implications for the origins of
short-period comets are substantially revised, and tedious material
on
statistical tests has been collected into a new Appendix
\\ ( http://arXiv.org/abs/astro-ph/0308467 , 592kb)
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\\
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The abundance of Galactic planets from OGLE-III 2002 microlensing data
Colin Snodgrass, Keith Horne, Yiannis Tsapras
Monthly Notices of the Royal Astronomical Society; Volume 351, Issue
3,
Page 967
http://www.blackwell-synergy.com/links/doi/10.1111/j.1365-2966.2004.07839.x
------------------------------------------------------------------------
------------------------------------------------------------------------
First sources in infrared light: stars, supernovae and miniquasars
Asantha Cooray, Naoki Yoshida
Monthly Notices of the Royal Astronomical Society; Volume 351, Issue
3,
Page L71
http://www.blackwell-synergy.com/links/doi/10.1111/j.1365-2966.2004.08047.x
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\\
Paper: astro-ph/0402659
Date: Fri, 27 Feb 2004 15:49:41 GMT (161kb)
Title: 1E 1207.4-5209: a low-mass bare strange star?
Authors: R. X. Xu (PKU)
Comments: 26 pages, 5 figures, submitted
Both rotation- and accretion-powered low-mass bare strange stars are
studied, the astrophysical appearances of which are especially
focused. It is suggested that low-mass bare strange stars, with weaker
ferromagnetic fields than that of normal pulsars, could result from
accretion-induced collapses (AIC) of white dwarfs. According to its
peculiar timing behavior, we propose that the radio-quiet object, 1E
1207.4-5209, could be a low-mass bare strange star with polar surface
magnetic field ~ 6 x 10^10 G and a few kilometers in radius. The
low-mass bare strange star ideal is helpful to distinguish neutron and
strange stars, and is testable by imaging pulsar-like stars with the
future Constellation-X telescope.
\\ ( http://arXiv.org/abs/astro-ph/0402659 , 161kb)
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\\
Title: Redshift-Independent Distances to Type Ia Supernovae
Authors: Brian J. Barris and John L. Tonry
Comments: 12 pages, 3 figures, accepted for publication in
Astrophysical
Journal Letters
We describe a procedure for accurately determining luminosity
distances to Type Ia supernovae (SNe Ia) without knowledge of
redshift. This procedure, which may be used as an extension of any of
the various distance determination methods currently in use, is based
on marginalizing over redshift, removing the requirement of knowing
$z$ a priori. We demonstrate that the Hubble diagram scatter of
distances measured with this technique is approximately equal to that
of distances derived from conventional redshift-specific methods for a
set of 60 nearby SNe Ia. This indicates that accurate distances for
cosmological SNe Ia may be determined without the requirement of
spectroscopic redshifts, which are typically the limiting factor for
the number of SNe that modern surveys can collect. Removing this
limitation would greatly increase the number of SNe for which current
and future SN surveys will be able to accurately measure distance. The
method may also be able to be used for high-$z$ SNe Ia to determine
cosmological density parameters without redshift information.
\\ ( http://arXiv.org/abs/astro-ph/0408097 , 75kb)
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\\
Subgalactic Clumps at High Redshift: A Fragmentation Origin?
Andreas Immeli, Markus Samland, Pieter Westera, and Ortwin Gerhard
Page 20 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ17082 ]
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A Luminous Ly alpha -emitting Galaxy at Redshift z = 6.535: Discovery
and Spectroscopic Confirmation
James E. Rhoads, Chun Xu, Steve Dawson, Arjun Dey, Sangeeta Malhotra,
JunXian Wang, Buell T. Jannuzi, Hyron Spinrad, and Daniel Stern
Page 59 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ59984 ]
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\\
The Glow of Primordial Remnants
G. Chabrier
Page 315 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ59536
]
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The Cosmic Energy Inventory
Masataka Fukugita and P. J. E. Peebles
Page 643 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ60693 ]
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Paper: astro-ph/0412031
Date: Wed, 1 Dec 2004 19:26:34 GMT (326kb)
Title: Millimeter Wavelength Brightness Fluctuations of the Atmosphere Above
the South Pole
Authors: R. S. Bussmann, W. L. Holzapfel, C. L. Kuo
Comments: 13 pages, 15 figures, submitted to ApJ
We report measurements of the millimeter wavelength brightness
fluctuations produced by the atmosphere above the South Pole made with
the Arcminute Cosmology Bolometer Array Receiver (ACBAR). The data
span the 2002 Austral winter during which ACBAR was mounted on the
Viper telescope at the South Pole. We recover the atmospheric signal
in the presence of instrument noise by calculating the correlation
between signals from distinct elements of the ACBAR bolometer
array. With this method, it is possible to measure atmospheric
brightness fluctuations with high SNR even under the most stable
atmospheric conditions. The observed atmospheric signal is
characterized by the parameters of the Komolgorov-Taylor (KT) model,
which are the amplitude and power law exponent describing the
atmospheric power spectrum, and the two components of the wind angular
velocity at the time of the observation. The KT model is typically a
good description of the observed fluctuations, and fits to the data
produce values of the Komolgorov exponent that are consistent with
theoretical expectations. By combining the wind angular velocity
results with measurements of the wind linear velocity, we find that
the altitude of the observed atmospheric fluctuations is consistent
with the distribution of water vapor determined from radiosonde
data. For data corresponding to frequency passbands centered on 150,
219, and 274 GHz, we obtain median fluctuation power amplitudes of
[10, 38, 74] mK^{2} rad^{-5/3} in Rayleigh-Jeans temperature
units. Comparing with previous work, we find that these median
amplitudes are approximately an order of magnitude smaller than those
found at the South Pole during the Austral summer and at least 30
times lower than found at the ALMA site in the Atacama desert.
\\ ( http://arXiv.org/abs/astro-ph/0412031 , 326kb)
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Paper: astro-ph/0411034
replaced with revised version Thu, 2 Dec 2004 09:19:29 GMT (2kb)
Title: Has Dark Energy really been discovered in the Lab?
Authors: Philippe Jetzer and Norbert Straumann
Comments: The paper is accepted for publication in Physics Letters B;
added
equation 4
\\ ( http://arXiv.org/abs/astro-ph/0411034 , 2kb)
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Cosmological Parameters sigma 8, the Baryon Density
Omega b, the Vacuum Energy Density Omega Lamda
, the Hubble Constant and the UV Background Intensity from a
Calibrated Measurement of H I Ly alpha Absorption at z = 1.9
David Tytler, David Kirkman, John M. O'Meara, Nao Suzuki, Adam Orin,
Dan Lubin, Pascal Paschos, Tridivesh Jena, Wen-Ching Lin, Michael
L. Norman, and Avery Meiksin
Page 1 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ60257 ]
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Studying the Star Formation Histories of Galaxies in Clusters from Composite
Spectra
Alan Dressler, Augustus Oemler, Jr., Bianca M. Poggianti, Ian Smail, Scott
Trager, Stephen A. Shectman, Warrick J. Couch, and Richard S. Ellis
Page 867 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ60042 ]
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Paper: astro-ph/0412566
Date: Tue, 21 Dec 2004 16:03:03 GMT (219kb)
Title: Tracing the Warm Hot Intergalactic Medium in the local Universe
Authors: M. Viel, E. Branchini, R. Cen, J.P. Ostriker, S. Matarrese, P.
Mazzotta, B. Tully
Comments: 15 pages 11 Figures. Submitted to MNRAS
\\
We present a simple method for tracing the spatial distribution and
predicting the physical properties of the Warm-Hot Intergalactic Medium (WHIM),
from the map of galaxy light in the local universe. Under the assumption that
biasing is local and monotonic we map the ~ 2 Mpc/h smoothed density field of
galaxy light into the mass density field from which we infer the spatial
distribution of the WHIM in the local supercluster. Taking into account the
scatter in the WHIM density-temperature and density-metallicity relation,
extracted from the z=0 outputs of high-resolution and large box size
hydro-dynamical cosmological simulations, we are able to quantify the
probability of detecting WHIM signatures in the form of absorption features in
the X-ray spectra, along arbitrary directions in the sky. To illustrate the
usefulness of this semi-analytical method we focus on the WHIM properties in
the Virgo Cluster region.
\\ ( http://arXiv.org/abs/astro-ph/0412566 , 219kb)
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\\
Paper: astro-ph/0501088
Date: Thu, 6 Jan 2005 01:19:55 GMT (482kb)
Title: The Assembly of Diversity in the Morphologies and Stellar Populations of
High-Redshift Galaxies
Authors: Casey Papovich (1), Mark Dickinson (2,3,4), Mauro Giavalisco (3),
Christopher J. Conselice (5), Henry C. Ferguson (3,4) ((1) Steward Obs., (2)
NOAO, (3) STScI, (4) Johns Hopkins, (5) Caltech)
Comments: Accepted for publication in the Astrophysical Journal. 20 pages, in
emulateapj format
\\
We have studied the evolution in the morphologies, sizes, stellar-masses,
colors, and internal color dispersion (ICD) of galaxies at z=1 and 2.3, using a
near-IR, flux-limited catalog for the HDF-N. At z=1 most luminous galaxies have
morphologies of early-to-mid Hubble-types, and many show transformations
between their rest-frame UV-optical morphologies. Galaxies at z=2.3 have
compact and irregular morphologies with no clearly evident Hubble-sequence
candidates. The mean galaxy size grows from z=2.3 to 1 by 40%, and the density
of galaxies larger than 3 kpc increases by 7 times. At z=1, the size-luminosity
distribution is broadly consistent with that of local galaxies, with passive
evolution. However, galaxies at z=2.3 are smaller than the large present-day
galaxies, and must continue to grow in size and stellar mass. We have measured
the galaxies' UV-optical ICD, which quantifies differences in morphology and
the relative amount of on-going star-formation. The mean and scatter in
galaxies' total colors and ICD increase from z=2.3 to 1. At z=1 many galaxies
with large ICD are spirals, with a few irregular systems. Few z=2.3 galaxies
have high ICD, and those that do are actively merging. We interpret this as
evidence for the presence of older and more diverse stellar populations at z=1
that are not generally present at z>2. We conclude that the star-formation
histories of galaxies at z>2 are dominated by discrete, recurrent bursts, which
quickly homogenize the galaxies' stellar content, and are possibly associated
with mergers. The increase in the stellar-population diversification by z<1.4
implies that merger-induced starbursts occur less frequently than at higher
redshifts, and more quiescent star-forming modes dominate. This transition
coincides with the emergence of Hubble-sequence galaxies. [Abridged]
\\ ( http://arXiv.org/abs/astro-ph/0501088 , 482kb)
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\\
Paper: astro-ph/0501654
Date: Sat, 29 Jan 2005 16:19:26 GMT (136kb)
Title: A Galactic Plane Relative Extinction Map from 2MASS
Authors: D. Froebrich (1), T.P. Ray (1), G.C. Murphy (1), A. Scholz (2) ((1)
Dublin Institute for Advanced Studies, (2) University of Toronto)
Comments: 4 pages, 2 figures, A&A Letters accepted, version with high
resolution figures at http://www.dias.ie/~df
\\
We present three 14400 square degree relative extinction maps of the Galactic
Plane (|b|<20degrees) obtained from 2MASS using accumulative star counts (Wolf
diagrams). This method is independent of the colour of the stars and the
variation of extinction with wavelength. Stars were counted in 3.5'x3.5' boxes,
every 20". 1x1degree surrounding fields were chosen for reference, hence the
maps represent local extinction enhancements and ignore any contribution from
the ISM or very large clouds. Data reduction was performed on a Beowulf-type
cluster (in approximately 120 hours). Such a cluster is ideal for this type of
work as areas of the sky can be independently processed in parallel. We studied
how extinction depends on wavelength in all of the high extinction regions
detected and within selected dark clouds. On average a power law opacity index
(\beta) of 1.0 to 1.8 in the NIR was deduced. The index however differed
significantly from region to region and even within individual dark clouds.
That said, generally it was found to be constant, or to increase, with
wavelength within a particular region.
\\ ( http://arXiv.org/abs/astro-ph/0501654 , 136kb)
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\\
Paper: astro-ph/0406604
replaced with revised version Fri, 4 Feb 2005 18:27:16 GMT (968kb)
Title: A high-significance detection of non-Gaussianity in the WMAP
1-year data
using directional spherical wavelets
Authors: J. D. McEwen, M. P. Hobson, A. N. Lasenby and D. J. Mortlock
Comments: 14 pages, 10 figures, replaced to match version accepted by
MNRAS.
Title changed; extended to 1000 Monte Carlo simulations; chi-squared
test
added; cross-correlation analysis of localised regions added;
preliminary
noise analysis added. Main results unchanged
\\ ( http://arXiv.org/abs/astro-ph/0406604 , 968kb)
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The Discovery of a High-Redshift X-Ray-Emitting QSO Very Close to the
Nucleus of NGC 7319
Pasquale Galianni, E. M. Burbidge, H. Arp, V. Junkkarinen,
G. Burbidge, and Stefano Zibetti
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Paper: astro-ph/0503306
Date: Mon, 14 Mar 2005 23:21:24 GMT (106kb)
Title: Ice Age Epochs and the Sun's Path Through the Galaxy
Authors: D. R. Gies and J. W. Helsel
Comments: 14 pages, 3 figures, accepted for publication in ApJ
We present a calculation of the Sun's motion through the Milky Way
Galaxy over the last 500 million years. The integration is based upon
estimates of the Sun's current position and speed from measurements
with Hipparcos and upon a realistic model for the Galactic
gravitational potential. We estimate the times of the Sun's past
spiral arm crossings for a range in assumed values of the spiral
pattern angular speed. We find that for a difference between the mean
solar and pattern speed of Omega_Sun - Omega_p = 11.9 +/- 0.7 km/s/kpc
the Sun has traversed four spiral arms at times that appear to
correspond well with long duration cold periods on Earth. This
supports the idea that extended exposure to the higher cosmic ray flux
associated with spiral arms can lead to increased cloud cover and long
ice age epochs on Earth.
\\ ( http://arXiv.org/abs/astro-ph/0503306 , 106kb)
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Limits from the Hubble Space Telescope on a Point Source in SN 1987A
Genevieve J. M. Graves, Peter M. Challis, Roger A. Chevalier, Arlin
Crotts, Alexei V. Filippenko, Claes Fransson, Peter Garnavich, Robert
P. Kirshner, Weidong Li, Peter Lundqvist, Richard McCray, Nino
Panagia, Mark M. Phillips, Chun J. S. Pun, Brian P. Schmidt, George
Sonneborn, Nicholas B. Suntzeff, Lifan Wang, and J. Craig Wheeler
Page 944 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ62098
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Paper: astro-ph/0509630
Date: Wed, 21 Sep 2005 14:08:21 GMT (988kb)
Title: Research on candidates for non-cosmological redshifts
Authors: M. Lopez-Corredoira, C. M. Gutierrez
Categories: astro-ph
Comments: 18 pages, to be published in the proceedings of the
conference
"Crisis in Cosmology I", 23 to 25 June 2005, Moncao (Portugal)
(Abridged:) The paradox of apparent optical associations of galaxies
with very different redshifts, the so-called anomalous redshift
problem, is around 35 years old, but is still without a clear solution
and is surprisingly ignored by most of the astronomical
community. Statistical correlations among the positions of these
galaxies have been pointed out by several authors. Gravitational
lensing by dark matter has been proposed as the cause of these
correlations, although this seems to be insufficient to explain them
and does not work at all for correlations with the brightest and
nearest galaxies. Some of these cases may be just fortuitous
associations in which background objects are close in the sky to a
foreground galaxy, although the statistical mean correlations remain
to be explained and some lone objects have very small probabilities of
being a projection of background objects. The sample of discordant
redshift associations given in Arp's atlas is indeed quite large, and
most of the objects remain to be analysed thoroughly. For about 5
years, we have been running a project to observe some of these cases
in detail, and some new anomalies have been added to those already
known; For instance, in some exotic configurations such as NGC 7603 or
NEQ3, which can even show bridges connecting four object with very
different redshifts. Not only QSOs but also emission-line galaxies in
general are found to take part in this kind of event. Other cases are
analyzed: MCG 7-25-46, GC 0248+430, B2 1637+29, VV172 and Stephan's
Quintet.
\\ ( http://arXiv.org/abs/astro-ph/0509630 , 988kb)
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Ultralow-Amplitude Cepheids in the Large Magellanic Cloud
J. Robert Buchler, Peter R. Wood, Stefan Keller, and Igor Soszynski
Page L151 [
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The search for the host galaxy of the gamma-ray burst GRB 000214:
S. Guziy, J. Gorosabel, A. J. Castro-Tirado, A. de Ugarte Postigo,
M. Jelinek, M.
D. Perez Ramirez, J. M. Castro Ceron, S. Klose, E. Palazzi and
K. Wiersema
A&A 441 (2005) 975-979 (Section 'Extragalactic astronomy')
http://publish.edpsciences.org/abstract/aa/v441/p975
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Paper: astro-ph/0509713
Date: Fri, 23 Sep 2005 11:38:58 GMT (108kb)
Title: Fundamental limitations on Earth-like planet detection with
Extremely
Large Telescopes
Authors: C. Cavarroc, A. Boccaletti, P. Baudoz, T. Fusco, D. Rouan
Categories: astro-ph
Comments: 8 pages, 8 figures, accepted in A&A
We analyse the fundamental limitations for the detection of
extraterrestrial planets with Extremely Large Telescopes. For this
task, a coronagraphic device combined to a very high order wavefront
correction system is required but not sufficient to achieve the
$10^{-10}$ contrast level needed for detecting an Earth-like
planet. The stellar residuals left uncorrected by the wavefront
correction system need to be calibrated and subtracted. In this paper,
we consider a general model including the dynamic phase aberrations
downstream the wavefront correction system, the static phase
aberrations of the instrument and some differential aberrations
provided by the calibration unit. A rather optimistic case of a filled
circular pupil and of a perfect coronagraph is elsewhere assumed. As a
result of the analytical study, the limitation mostly comes from the
static aberrations. Using numerical simulations we confirm this result
and evaluate the requirements in terms of phase aberrations to detect
Earth-like planets on Extremely Large Telescopes.
\\ ( http://arXiv.org/abs/astro-ph/0509713 , 108kb)
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Paper: astro-ph/0509749
Date: Mon, 26 Sep 2005 12:25:16 GMT (321kb)
Title: The circumstellar environment of Wolf-Rayet stars & Gamma-ray
burst afterglows
Authors: J. J. Eldridge, F. Genet, F. Daigne & R. Mochkovitch
Categories: astro-ph
Comments: 35 pages, second draft changed by referees comments and
resubmitted to MNRAS
We study the evolution of the circumstellar medium of massive
stars. We pay particular attention to Wolf-Rayet stars that are
thought to be the progenitors of some long Gamma-Ray Bursts. We detail
the mass-loss rates we use in our stellar evolution models and how we
estimate the stellar wind speeds during different phases. With these
details we simulate the interactions between the wind and the
interstellar medium to predict the circumstellar environment around
the stars at the time of core-collapse. We then investigate how the
structure of the environment might affect the GRB afterglow. We find
that when the afterglow jet encounters the free-wind to stalled-wind
interface that rebrightening occurs and a bump is seen in the
afterglow light curve. However our predicted positions of this
interface are too distant from the site of the GRB to reach while the
afterglow remains observable. The values of the final-wind density,
A_{*}, from our stellar models are similar to the values inferred from
observed afterglow lightcurves and those from observed Wolf-Rayet
stars. However we do not reproduce the lowest observed A_{*} values
below 0.3. For these cases we suggest that the progenitors could have
been a WO type Wolf-Rayet star, be in a close binary or very low
metallicity star. Finally we turn our attention to the matter of
stellar wind material producing absorption lines in the afterglow
spectra. We discuss the observational signatures of two Wolf-Rayet
stellar types, WC and WO, in the afterglow lightcurve and spectra. We
also indicate how it may be possible to constrain the initial mass and
metallicity of a GRB progenitor by using the inferred wind density and
wind velocity.
\\ ( http://arXiv.org/abs/astro-ph/0509749 , 321kb)
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Paper: astro-ph/0509737
Date: Sat, 24 Sep 2005 09:45:33 GMT (61kb)
Title: Detection of a huge explosion in the early Universe
Authors: G. Cusumano, V. Mangano, G. Chincarini, A. Panaitescu,
D.N. Burows, V. La Parola, T. Sakamoto, S. Campana, T. Mineo,
G. Tagliaferri, L. Angelini, S.D. Barthelemy, A.P. Beardmore,
P.T. Boyd, L. Cominsky, C. Gronwall, E.E. Fenimore, N. Gehrels,
P. Giommi, M. Goad, K. Hurley, J.A. Kennea, K.O. Mason, F. Marshall,
P. Meszaros, J.A. Nousek, J.P. Osborne, D.M. Palmer, P.W.A. Roming,
A. Wells, N.E. White, B. Zhang
Categories: astro-ph
Comments: 11 pages, 1 table, 3 figures. Note: this paper has been
submitted for publication in Nature, It is embargoed for discussion in
the popular press
Gamma-ray Bursts (GRBs) are bright flashes of high energy photons that
can last from about 10 milliseconds to 10 minutes. Their origin and
nature have puzzled the scientific community for about 25 years until
1997, when the first X-ray afterglows of long (> 2 s duration) bursts
were detected and the first optical and radio counterparts were
found. These measurements established that long GRBs are typically at
high redshift (z 1.6) and are in sub-luminous star-forming host
galaxies. They are likely produced in core-collapse explosions of a
class of massive stars that give rise to highly relativistic jets
(collapsar model). Internal inhomogeneities in the velocity field of
the relativistic expanding flow lead to collisions between fast moving
and slow moving fluid shells and to the formation of internal shock
waves. These shocks are believed to produce the observed prompt
emission in the form of irregularly shaped and spaced pulses of
gamma-rays, each pulse corresponding to a distinct internal
collision. The expansion of the jet outward into the circumstellar
medium is believed to give rise to ``external'' shocks, responsible
for producing the smoothly fading afterglow emission seen in the
X-ray, optical and radio bands. Here we report on the gamma-ray and
x-ray observation of the most distant gamma-ray burst ever observed:
its redshift of 6.29 translates to a distance of 13 billion
light-years from Earth, corresponding to a time when the Universe was
just 700 million to 750 million years old. The discovery of a
gamma-ray burst at such a large redshift implies the presence of
massive stars only 700 million years after the Big Bang. The very high
redshift bursts represent a good way to study the re-ionization era
soon after the Universe came out of the Dark Ages.
\\ ( http://arXiv.org/abs/astro-ph/0509737 , 61kb)
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Paper: astro-ph/0509120
Date: Tue, 6 Sep 2005 13:07:38 GMT (717kb)
Title: Discovery of Ultra-Compact Dwarf Galaxies in the Virgo Cluster
Authors: J. B. Jones, M. J. Drinkwater, R. Jurek, S. Phillipps,
M. D. Gregg, K. Bekki, W. J. Couch, A. Karick, Q. A. Parker,
R. M. Smith
Comments: 26 pages; 12 figures; accepted for publication in the
Astronomical Journal
We have discovered nine ultra-compact dwarf galaxies (UCDs) in the
Virgo Cluster, extending samples of these objects outside the Fornax
Cluster. Using the 2dF multi-fiber spectrograph on the
Anglo-Australian Telescope, the new Virgo members were found among
1500 color-selected, star-like targets with 16.0 < b_j < 20.2 in a
two-degree diameter field centered on M87 (NGC4486). The newly-found
UCDs are comparable to the UCDs in the Fornax Cluster, with sizes <~
100 pc, -12.9 < M_B < -10.7, and exhibiting red, absorption-line
spectra, indicative of an older stellar population. The properties of
these objects remain consistent with the tidal threshing model for the
origin of UCDs from the surviving nuclei of nucleated dwarf
ellipticals disrupted in the cluster core, but can also be explained
as objects that were formed by mergers of star clusters created in
galaxy interactions. The discovery that UCDs exist in Virgo shows that
this galaxy type is probably a ubiquitous phenomenon in clusters of
galaxies; coupled with their possible origin by tidal threshing, the
UCD population is a potential indicator and probe of the formation
history of a given cluster. We also describe one additional bright
UCD with M_B = -12.0 in the core of the Fornax Cluster. We find no
further UCDs in our Fornax Cluster Spectroscopic Survey down to b_j =
19.5 in two additional 2dF fields extending as far as 3 degrees from
the center of the cluster. All six Fornax bright UCDs identified with
2dF lie within 0.5 degree (projected distance of 170 kpc) of the
central elliptical galaxy NGC1399.
\\ ( http://arXiv.org/abs/astro-ph/0509120 , 717kb)
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Paper: astro-ph/0509152
Date: Tue, 6 Sep 2005 23:34:36 GMT (64kb)
Title: Galactic Open Clusters
Authors: Ted von Hippel
Comments: 14 pages, to appear in Resolved Stellar Populations, ASP
Conference in Cancun
The study of open clusters has a classic feel to it since the subject
predates anyone alive today. Despite the age of this topic, I show via
an ADS search that its relevance and importance in astronomy has grown
faster in the last few decades than astronomy in general. This is
surely due to both technical reasons and the interconnection of the
field of stellar evolution to many branches of astronomy. In this
review, I outline what we know today about open clusters and what they
have taught us about a range of topics from stellar evolution to
Galactic structure to stellar disk dissipation timescales. I argue
that the most important astrophysics we have learned from open
clusters is stellar evolution and that its most important product has
been reasonably precise stellar ages. I discuss where open cluster
research is likely to go in the next few years, as well as in the era
of 20m telescopes, SIM, and GAIA. Age will continue to be of wide
relevance in astronomy, from cosmology to planet formation timescales,
and with distance errors soon no longer a problem, improved ages will
be critically important to many of the most fascinating astrophysical
questions.
\\ ( http://arXiv.org/abs/astro-ph/0509152 , 64kb)
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Paper: astro-ph/0510012
Date: Sat, 1 Oct 2005 00:19:14 GMT (809kb)
Title: Results from the Wide Angle Search for Planets Prototype
(WASP0) III: Planet Hunting in the Draco Field
Authors: Stephen R. Kane, Andrew Collier Cameron, Keith Horne, David
James, T. A. Lister, Don L. Pollacco, Rachel A. Street, Yiannis
Tsapras Categories: astro-ph
Comments: 14 pages, 14 figures (some degraded to fit file size
limits), Accepted for publication in MNRAS
The Wide Angle Search for Planets prototype (WASP0) is a wide-field
instrument used to search for extra-solar planets via the transit
method. Here we present the results of a monitoring program which
targeted a 9-degree field in Draco. WASP0 monitored 35000 field stars
for two consecutive months. Analysis of the lightcurves resulted in
the detection of 11 multi-transit candidates and 3 single-transit
candidates, two of which we recommend for further
follow-up. Monte-Carlo simulations matching the observing parameters
estimate the expected number of transit candidates from this survey. A
comparison of the expected number with the number of candidates
detected is used to discuss limits on planetary companions to field
stars.
\\ ( http://arXiv.org/abs/astro-ph/0510012 , 809kb)
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Paper: astro-ph/0510150
Date: Wed, 5 Oct 2005 20:35:39 GMT (163kb)
Title: Identifying Very Metal-Rich Stars with Low-Resolution Spectra:
Finding Planet-Search Targets
Authors: Sarah E. Robinson (1), Jay Strader (1), S. Mark Ammons (1),
Gregory Laughlin (1), and Debra Fischer (2) ((1) UCO/Lick Observatory,
Department of Astronomy and Astrophysics, University of California at
Santa Cruz, (2) Department of Physics and Astronomy, San Francisco
State University)
Categories: astro-ph
Comments: Accepted for publication in the Astrophysical Journal
We present empirical calibrations that estimate stellar metallicity,
effective temperature and surface gravity as a function of Lick/IDS
indices. These calibrations have been derived from a training set of
261 stars for which (1) high-precision measurements of [Fe/H], T_eff
and log g have been made using spectral-synthesis analysis of HIRES
spectra, and (2) Lick indices have also been measured. Our [Fe/H]
calibration, which has precision 0.07 dex, has identified a number of
bright (V < 9) metal-rich stars which are now being screened for hot
Jupiter-type planets. Using the Yonsei-Yale stellar models, we show
that the calibrations provide distance estimates accurate to 20% for
nearby stars. This paper outlines the second tier of the screening of
planet-search targets by the N2K Consortium, a project designed to
identify the stars most likely to harbor extrasolar
planets. Discoveries by the N2K Consortium include the transiting hot
Saturn HD 149026 b (Sato et al. 2005, astro-ph/0507009) and HD 88133 b
(Fischer et al. 2005). See Ammons et al. (2005, In Press) for a
description of the first tier of N2K metallicity screening,
calibrations using broadband photometry.
\\ ( http://arXiv.org/abs/astro-ph/0510150 , 163kb)
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Paper: astro-ph/0510307
replaced with revised version Wed, 12 Oct 2005 16:10:13 GMT (546kb)
Title: Luminous AGB stars in nearby galaxies. A study using Virtual
Observatory tools
Authors: P. Tsalmantza, E. Kontizas, L. Cambresy, F. Genova,
A. Dapergolas, and M. Kontizas
Comments: 16 pages, 12 figures, 4 tables (Appendix A), accepted in A&A
\\ ( http://arXiv.org/abs/astro-ph/0510307 , 546kb)
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Paper: astro-ph/0510581
Date: Wed, 19 Oct 2005 18:08:25 GMT (209kb)
Title: Detection of a Hot Binary Companion of $\eta$ Carinae
Authors: Rosina C. Iping, George Sonneborn, Theodore R. Gull, Derck
L. Massa and D. John Hillier
We report the detection of a hot companion of $\eta$ Carinae using
high resolution spectra (905 - 1180 \AA) obtained with the Far
Ultraviolet Spectroscopic Explorer (\fuse) satellite. Observations
were obtained at two epochs of the 2024-day orbit: 2003 June during
ingress to the 2003.5 X-ray eclipse and 2004 April several months
after egress. These data show that essentially all the far-UV flux
from \etacar shortward of \lya disappeared at least two days before
the start of the X-ray eclipse (2003 June 29), implying that the hot
companion, \etaB, was also eclipsed by the dense wind or extended
atmosphere of \etaA. Analysis of the far-UV spectrum shows that \etaB
is a luminous hot star. The \nii \wll1084-1086 emission feature
suggests that it may be nitrogen-rich. The observed far-UV flux levels
and spectral features, combined with the timing of their
disappearance, is consistent with \etacar\ being a massive binary
system.
\\ ( http://arXiv.org/abs/astro-ph/0510581 , 209kb)
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Paper: astro-ph/0510815
Date: Fri, 28 Oct 2005 19:21:06 GMT (31kb)
Title: An anomalous concentration of QSOs around NGC 3079
Authors: E.M. Burbidge, G. Burbidge, H.C. Arp, W.M. Napier
Comments: 5 pages, 4 figures, 2 tables
It is shown that there are at least 21 QSOs within 1 degree of the
nearby active spiral galaxy NGC3079. Many of them are bright (mag<18)
so that the surface density of those closer than 15 arc minutes to the
galaxy centre is close to 100 times the average in the field. The
probability that this is an accidental configuration is shown to be
less or equal to one in a million. Discovery selection effects and
microlensing fail by a large factor to explain the phenomenon,
suggesting that the QSOs may lie in the same physical space as
NGC3079. However, two of them make up the apparently lensed pair
0957+561A, B whose lensing galaxy lies at z=0.355. This problem is
discussed in the concluding section.
\\ ( http://arXiv.org/abs/astro-ph/0510815 , 31kb)
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Paper: astro-ph/0510844
Date: Mon, 31 Oct 2005 11:26:54 GMT (996kb)
Title: Massive Science with VO and Grids
Authors: Robert Nichol (ICG Portsmouth), Garry Smith (ICG & IoA),
Christopher Miller (NOAO), Peter Freeman, Chris Genovese, Larry
Wasserman (Stats CMU), Brent Bryan, Alexander Gray, Jeff Schneider,
Andrew Moore (CS CMU)
Comments: Invited talk at ADASSXV conference published as ASP
Conference Series, Vol. XXX, 2005 C. Gabriel, C. Arviset, D. Ponz and
E. Solano, eds. 9 pages
There is a growing need for massive computational resources for the
analysis of new astronomical datasets. To tackle this problem, we
present here our first steps towards marrying two new and emerging
technologies; the Virtual Observatory (e.g, AstroGrid) and the
computational grid (e.g. TeraGrid, COSMOS etc.). We discuss the
construction of VOTechBroker, which is a modular software tool
designed to abstract the tasks of submission and management of a large
number of computational jobs to a distributed computer system. The
broker will also interact with the AstroGrid workflow and MySpace
environments. We discuss our planned usages of the VOTechBroker in
computing a huge number of n-point correlation functions from the SDSS
data and massive model-fitting of millions of CMBfast models to WMAP
data. We also discuss other applications including the determination
of the XMM Cluster Survey selection function and the construction of
new WMAP maps.
\\ ( http://arXiv.org/abs/astro-ph/0510844 , 996kb)
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Title: The Distance to the Perseus Spiral Arm in the Milky Way
Authors: Y. Xu (NJU, Cfa, Shao), M. J. Reid (CfA), X. W. Zheng (NJU),
K. M. Menten (MPIfR)
Comments: 19 pages, 4 figures, Science Express December 8, 2005
We have measured the distance to the massive star-forming region W3OH
in the Perseus spiral arm of the Milky Way to be 1.95 $\pm$ 0.04
kilo-parsecs ($5.86\times10^{16}$ km). This distance was determined by
triangulation, with the Earth's orbit as one segment of a triangle,
using the Very Long Baseline Array. This resolves a long-standing
problem of a factor of two discrepancy between different techniques to
determine distances. The reason for the discrepancy is that this
portion of the Perseus arm has anomalous motions. The orientation of
the anomalous motion agrees with spiral density-wave theory, but the
magnitude is somewhat larger than most models predict.
\\ ( http://arXiv.org/abs/astro-ph/0512223 , 348kb)
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Paper: astro-ph/0512191
Date: Wed, 7 Dec 2005 16:02:03 GMT (33kb)
Title: 10 New Very Low Mass Close Binaries Resolved in the Visible
Authors: Nicholas M. Law (1), Simon T. Hodgkin (1), Craig D. Mackay
(1), John E. Baldwin (2) ((1) IOA University of Cambridge, (2)
Cavendish Astrophysics Group University of Cambridge)
Comments: Accepted to Astron. Nachr
Journal-ref: AN 326, No. 10, 1024-1025 (2005)
DOI: 10.1002/asna.200510455
We present preliminary results from the first part of the LuckyCam
late M-dwarf binarity survey. We survey a sample of 48 nearby ($<$40
pc) and red (M5-M9) stars with the novel high angular resolution
visible light imaging technique Lucky Imaging, in only 8 hours of 2.5m
telescope time. We discover 10 new binaries; although the survey is
sensitive to brown dwarf companions none are detected. The orbital
radius distribution of the newly discovered binaries broadly matches
that of previous detections by other groups, although we do discover
one wide binary at ~40AU.
\\ ( http://arXiv.org/abs/astro-ph/0512191 , 33kb)
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The afterglow and elliptical host galaxy of the short [gamma]-ray
burst GRB 050724
E. Berger et al.
Abstract: http://info.nature.com/cgi-bin24/DM/y/eWH50BhW230Ch0rVq0E4
Article: http://info.nature.com/cgi-bin24/DM/y/eWH50BhW230Ch0rVU0Eb
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An origin in the local Universe for some short [gamma]-ray bursts
N. R. Tanvir, R. Chapman, A. J. Levan and R. S. Priddey
Abstract: http://info.nature.com/cgi-bin24/DM/y/eWH50BhW230Ch0rVs0E6
Article: http://info.nature.com/cgi-bin24/DM/y/eWH50BhW230Ch0rVV0Ec
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An origin for short [gamma]-ray bursts unassociated with current star
formation
S. D. Barthelmy et al.
Abstract: http://info.nature.com/cgi-bin24/DM/y/eWH50BhW230Ch0rVu0E8
Article: http://info.nature.com/cgi-bin24/DM/y/eWH50BhW230Ch0rVW0Ed
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Optical and Infrared Nondetection of the z = 10 Galaxy behind Abell
1835
Graham P. Smith, David J. Sand, Eiichi Egami, Daniel Stern, and Peter
R. Eisenhardt
Page 575 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ62380
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Paper: astro-ph/0512403
replaced with revised version Mon, 16 Jan 2006 17:17:15 GMT (19kb)
Title: The Infrared Glow of First Stars
Authors: R. Salvaterra, M. Magliocchetti, A. Ferrara, R. Schneider
Comments: 4 pages, 2 figures, MNRAS in press
\\ ( http://arXiv.org/abs/astro-ph/0512403 , 19kb)
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Paper: astro-ph/0601432
Date: Thu, 19 Jan 2006 15:02:03 GMT (49kb)
Title: A Catalogue of RR Lyrae Stars from the Northern Sky Variability
Survey
Authors: Patrick Wils, Chris Lloyd, Klaus Bernhard
Comments: Submitted to MNRAS
A search for RR Lyrae stars has been conducted in the publicly
available data of the Northern Sky Variability Survey
(NSVS). Candidates have been selected by the statistical properties of
their variation; the standard deviation, skewness and kurtosis with
appropriate limits determined from a sample 314 known RRab and RRc
stars listed in the GCVS. From the period analysis and light curve
shape of over 3000 candidates 785 RR Lyrae have been identified of
which 188 are previously unknown. The light curves were examined for
the Blazhko effect and several new stars showing this were
found. Seven double-mode RR Lyrae stars were also found of which three
are new discoveries. Some previously known variables have been
reclassified as RR Lyrae stars and similarly some RR Lyrae stars have
been found to be other types of variable, or not variable at all.
\\ ( http://arXiv.org/abs/astro-ph/0601432 , 49kb)
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Paper: astro-ph/0601494
Date: Mon, 23 Jan 2006 19:47:18 GMT (670kb)
Title: The true nature of CSL-1
Authors: M.V. Sazhin, M. Capaccioli, G. Longo, M. Paolillo,
O.S. Khovanskaya, N.A. Grogin, E.J. Schreier, G. Covone
Comments: 5 pages, 3 figures - Download postscript version for higher
quality images High resolution version at:
http://people.na.infn.it/~paolillo/publications.html
On January 12 2006, the Hubble Space Telescope observed the peculiar
double extragalactic object CSL-1, suspected to be the result of
gravitational lensing by a cosmic string. The high resolution image
shows that the object is actually a pair of interacting giant
elliptical galaxies. In spite of the weird similarities of the energy
and light distributions and of the radial velocities of the two
components, CSL-1 is not the lensing of an elliptical galaxy by a
cosmic string.
http://arXiv.org/abs/astro-ph/0601494
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Paper: astro-ph/0601563
Date: Wed, 25 Jan 2006 01:39:42 GMT (541kb)
Title: Discovery of a Cool Planet of 5.5 Earth Masses Through
Gravitational Microlensing
Authors: J.-P. Beaulieu, D.P. Bennett, P. Fouque, A. Williams,
M. Dominik, U.G. Jorgensen, D. Kubas, A. Cassan, C. Coutures,
J. Greenhill, K. Hill, J. Menzies, P.D. Sackett, M. Albrow,
S. Brillant, J.A.R. Caldwell, J.J. Calitz, K.H. Cook, E. Corrales,
M. Desort, S. Dieters, D. Dominis, J. Donatowicz, M. Hoffman,
S. Kane, J.-B. Marquette, R. Martin, P. Meintjes, K. Pollard, K.
Sahu, C. Vinter, J. Wambsganss, K. Woller, K. Horne, I. Steele,
D. Bramich, M. Burgdorf, C. Snodgrass, M. Bode (PLANET) A. Udalski,
M. Szymanski, M. Kubiak, T. Wieckowski, G. Pietrzynski, I. Soszynski,
O. Szewczyk, L. Wyrzykowski, B. Paczynski (OGLE), and the MOA
Collaboration
In the favoured core-accretion model of formation of planetary
systems, solid planetesimals accumulate to build up planetary cores,
which then accrete nebular gas if they are sufficiently
massive. Around M-dwarf stars (the most common stars in our Galaxy),
this model favours the formation of Earth-mass to Neptune-mass planets
with orbital radii of 1 to 10 astronomical units (AU), which is
consistent with the small number of gas giant planets known to orbit
M-dwarf host stars. More than 170 extrasolar planets have been
discovered with a wide range of masses and orbital periods, but
planets of Neptune's mass or less have not hitherto been detected at
separations of more than 0.15 AU from normal stars. Here we report the
discovery of a 5.5 (+5.5/-2.7) M_earth planetary companion at a
separation of 2.6 (+1.5/-0.6) AU from a 0.22 (+0.21/-0.11) M_solar
M-dwarf star. (We propose to name it OGLE-2005-BLG-390Lb, indicating a
planetary mass companion to the lens star of the microlensing event.)
The mass is lower than that of GJ876d, although the error bars
overlap. Our detection suggests that such cool, sub-Neptune-mass
planets may be more common than gas giant planets, as predicted by the
core accretion theory.
http://arXiv.org/abs/astro-ph/0601563
------------------------------------------------------------------------------
Luminous AGB stars in nearby galaxies - A study using virtual
observatory tools:
P. Tsalmantza, E. Kontizas, L. Cambresy, F. Genova, A. Dapergolas and
M. Kontizas
A&A 447 (2006) 89-95 (Section 'Astrophysical processes')
http://publish.edpsciences.org/abstract/aa/v447/p89
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Paper: astro-ph/0601633
Date: Fri, 27 Jan 2006 02:44:00 GMT (226kb)
Title: Spectacular Spitzer images of the Trifid Nebula: Protostars in
a young, massive-star-forming region
Authors: J. Rho, W. T. Reach (Spitzer Science Center/CalTech),
B. Lefloch (Laboratoire d'Astrophysique, Observatoire de Grenoble) and
G. Fazio (Harvard-Smithsonian Center for Astrophysics)
Comments: Accepted for publication in ApJ. Full resolution images are
available at http://spider.ipac.caltech.edu/staff/rho/
Spitzer IRAC and MIPS images of the Trifid Nebula (M20) reveal its
spectacular appearance in infrared light, highlighting the nebula's
special evolutionary stage. The images feature recently-formed massive
protostars and numerous young stellar objects, and a single O star
that illuminates the surrounding molecular cloud from which it formed,
and unveil large-scale, filamentary dark clouds. The hot dust grains
show contrasting infrared colors in shells, arcs, bow-shocks and dark
cores. Multiple protostars are detected in the infrared, within the
cold dust cores of TC3 and TC4, which were previously defined as Class
0. The cold dust continuum cores of TC1 and TC2 contain only one
protostar each. The Spitzer color-color diagram allowed us to identify
~160 young stellar objects and classify them into different
evolutionary stages. The diagram also revealed a unique group of YSOs
which are bright at 24 micron but have the spectral energy
distribution peaking at 5-8 micron. Despite expectation that Class 0
sources would be "starless" cores, the Spitzer images, with
unprecedented sensitivity, uncover mid-infrared emission from these
Class 0 protostars. The mid-infrared detections of Class 0 protostars
show that the emission escapes the dense, cold envelope of young
protostars. The mid-infrared emission of the protostars can be fit by
two temperatures of 150 and 400 K; the hot core region is probably
optically thin in the mid-infrared regime, and the size of hot core is
much smaller than that of the cold envelope. The presence of multiple
protostars within the cold cores of Class 0 objects implies that
clustering occurs at this early stage of star formation. The TC3
cluster shows that the most massive star is located at the center of
the cluster and at the bottom of the gravitational-potential well.
\\ ( http://arXiv.org/abs/astro-ph/0601633 , 226kb)
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McComas, D. J., and N. A. Schwadron (2006), An explanation
of the Voyager paradox: Particle acceleration at a blunt termination
shock, Geophys. Res. Lett., 33, L04102, doi:10.1029/2005GL025437.
http://www.agu.org/journals/gl/gl0604/2005GL025437/
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Paper: astro-ph/0603690
Date: Mon, 27 Mar 2006 20:57:14 GMT (131kb)
Title: Cross-correlation of WMAP 3rd year and the SDSS DR4 galaxy
survey: new evidence for Dark Energy
Authors: A.Cabre, E.Gaztanaga, M.Manera, P.Fosalba, F.Castander
(IEEC/CSIC)
Comments: 5 pages, 5 figures, submitted to MNRAS Letter
We cross-correlate the third-year WMAP data with galaxy samples
extracted from the SDSS DR4 covering 13% of the sky, increasing by a
factor of 3.7 the volume sampled in previous analyses. The new
measurements confirm a positive cross-correlation with higher
significance (total signal-to-noise of about 4.7). The correlation as
a function of angular scale is well fitted by the integrated
Sachs-Wolfe (ISW) effect for LCDM flat FRW models with a cosmological
constant (w=-1). The combined analysis of different samples gives
Omega_L=0.75-0.80 (68% Confidence Level, CL) or 0.70-0.82 (95% CL). We
find that the best fit Omega_L decreases from 0.82 to 0.75 (95% CL)
when we increase the median redshift of the galaxy sample from z~0.3
to z~0.5. The quick drop of the measured signal with z is too fast for
the LCDM cosmology. The data can be better reconciled with a model
with an effective dark energy equation of state w<-1.5. Such phantom
cosmology reduces by up to ~20% the amplitude of the lower multipoles
of the CMB temperature anisotropies with respect the w=-1 prediction,
which also brings the models closer to the observations.
\\ ( http://arXiv.org/abs/astro-ph/0603690 , 131kb)
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Paper: astro-ph/0604461
Date: Fri, 21 Apr 2006 09:25:49 GMT (211kb)
Title: Detection of Wolf-Rayet stars in host galaxies of Gamma-Ray
Bursts (GRBs): are GRBs produced by runaway massive stars ejected from
high stellar density regions ?
Authors: F. Hammer (1), H. Flores (1), D. Schaerer (2,3),
M. Dessauges-Zavadsky (2), E. Le Floc'h (4,1), and M. Puech (1)
Comments: (1) GEPI, Observatoire de Paris-Meudon, France, (2)
Observatoire de Geneve, Switzerland, (3) Laboratoire d'Astrophysique
Toulouse-Tarbes, France,(4) Steward Observatory, University of
Arizona, USA
We have obtained deep spectroscopic observations of several nearby
gamma-ray burst (GRB) host galaxies revealing for the first time the
presence of Wolf-Rayet (WR) stars and numerous O stars located in rich
and compact clusters or star forming regions. Surprisingly, high
spatial resolution imaging shows that the GRBs and the associated
supernovae did not occur in these regions, but several hundreds of
parsec away. Considering various scenarios for GRB progenitors, we do
not find any simple explanation of why they should be preferentially
born in regions with low stellar densities. All the examined GRBs and
associated SNe have occurred 400 to 800 pc from very high density
stellar environments including large numbers of WR stars. Such
distances can be travelled through at velocities of 100 km/s or
larger, assuming the travel time to be the typical life time of WR
stars. It leads us to suggest that GRB progenitors may be runaway
massive stars ejected from compact massive star clusters. The ejection
from such super star clusters may lead to a spin-up of these stars,
producing the loss of the hydrogen and/or helium envelopes leading to
the origin of the type Ibc supernovae associated with GRBs. If this
scenario applies tocd text/Sc all GRBs, it provides a natural
explanation of the very small fraction of massive stars that emit a
GRB at the end of their life. An alternative to this scenario could be
a binary origin for GRBs, but this still requires an explanation of
why it would preferentially occur in low stellar density regions.
\\ ( http://arXiv.org/abs/astro-ph/0604461 , 211kb)
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Paper: astro-ph/0604354
Date: Mon, 17 Apr 2006 18:54:53 GMT (232kb)
Title: A New Milky Way Dwarf Satellite in Canes Venatici
Authors: D. B. Zucker (1), V. Belokurov (1), N. W. Evans (1),
M. I. Wilkinson (1), M. J. Irwin (1), T. Sivarani (2), S. Hodgkin (1),
D. M. Bramich (1), J. M. Irwin (1), G. Gilmore (1), B. Willman (3),
S. Vidrih (1), M. Fellhauer (1), P. C. Hewett (1), T. C. Beers (2),
E. F. Bell (4), E. K. Grebel (5), D. P. Schneider (6), H. J. Newberg
(7), R. F. G. Wyse (8), C. M. Rockosi (9), B. Yanny (10), R. Lupton
(11), J. A. Smith (12), J. C. Barentine (13), H. Brewington (13),
J. Brinkmann (13), M. Harvanek (13), S. J.Kleinman (13), J.
Krzesinski (13,14), D. Long (13), A. Nitta (13), S. A. Snedden (13)
((1) Cambridge University, (2) Michigan State University, (3) New York
University, (4) MPIA, Heidelberg, (5) University of Basel, (6)
Pennsylvania State University, (7) Rensselaer Polytechnic Institute,
(8) JHU, (9) Lick Observatory/UCSC, (10) FNAL, (11) Princeton
University, (12) LANL, (13) Apache Point Observatory, (14) Cracow
Pedagogical University)
Comments: 4 pages, 4 figures; submitted to ApJ Letters
In this Letter, we announce the discovery of a new dwarf satellite of
the Milky Way, located in the constellation Canes Venatici. It was
found as a stellar overdensity in the North Galactic Cap using Sloan
Digital Sky Survey Data Release 5 (SDSS DR5). The satellite's
color-magnitude diagram shows a well-defined red giant branch, as well
as a horizontal branch. As judged from the tip of the red giant
branch, it lies at a distance of ~220 kpc. Based on the SDSS data, we
estimate an absolute magnitude of Mv ~ -7.9, a central surface
brightness of mu_0,V ~ 28 mag arcsecond^-2, and a half-light radius of
\~ 8.5' (~ 550 pc at the measured distance). The outer regions of
Canes Venatici appear extended and distorted. The discovery of such a
faint galaxy in proximity to the Milky Way strongly suggests that more
such objects remain to be found.
\\ ( http://arXiv.org/abs/astro-ph/0604354 , 232kb)
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Paper: astro-ph/0604355
Date: Mon, 17 Apr 2006 17:14:48 GMT (279kb)
Title: A Faint New Milky Way Satellite in Bootes
Authors: V. Belokurov (1), D. B. Zucker (1), N. W. Evans (1),
M. I. Wilkinson (1), M. J. Irwin (1), S. Hodgkin (1), D. M. Bramich
(1), J. M. Irwin (1), G. Gilmore (1), B. Willman (2), S. Vidrih (1),
H. J. Newberg (3), R. F. G. Wyse (4), M. Fellhauer (1), P. C. Hewett
(1), N. Cole (3), E. F. Bell (5), T. C. Beers (6), C. M. Rockosi (7),
B. Yanny (8), E. K. Grebel (9), D. P. Schneider (10), R. Lupton (11),
J. C. Barentine (12), H. Brewington (12), J. Brinkmann (12),
M. Harvanek (12), S. J.Kleinman (12), J. Krzesinski (12,13), D. Long
(12), A. Nitta (12), J. A. Smith (14), S. A. Snedden (12) ((1)
Cambridge University, (2) New York University, (3) Rensselaer
Polytechnical Institute, (4) JHU, (5) MPIA, Heidelberg, (6) Michigan
State University, (7) Lick Observatory, UCSC, (8) FNAL, (9) University
of Basel, (10) Pennsylvania State University, (11) Princeton
University, (12) Apache Point Observatory, (13) Cracow Pedagogical
University, (14) LANL)
Comments: Submitted to ApJ (Letters)
In this Letter, we announce the discovery of a new satellite of the
Milky Way in the constellation of Bootes at a distance of 60 kpc. It
was found in a systematic search for stellar overdensities in the
North Galactic Cap using Sloan Digital Sky Survey Data Release 5 (SDSS
DR5). The color-magnitude diagram shows a well-defined turn-off, red
giant branch, and extended horizontal branch. Its absolute magnitude
is -5.7, which makes it fainter than the faintest galaxy known. The
half-light radius is 220 pc. The isodensity contours are elongated and
have an irregular shape.
\\ ( http://arXiv.org/abs/astro-ph/0604355 , 279kb)
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Branes: cosmological surprise and observational deception:
S. Fay
A&A 452 (2006) 781-794 (Section 'Cosmology (including clusters of galaxies)')
http://publish.edpsciences.org/abstract/aa/v452/p781
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Dynamical Stability and Habitability of the gamma Cephei
Binary-Planetary System
Nader Haghighipour
Page 543 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ63716
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Spectrum of a Habitable World: Earthshine in the Near-Infrared
Margaret C. Turnbull, Wesley A. Traub, Kenneth W. Jucks, Neville
J. Woolf, Michael R. Meyer, Nadya Gorlova, Michael F. Skrutskie, and
John C. Wilson
Page 551 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ64090
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Detectability of Red-Edge-shifted Vegetation on Terrestrial Planets
Orbiting M Stars
Giovanna Tinetti, Sky Rashby, and Yuk L. Yung
Page L129 [
http://www.journals.uchicago.edu/cgi-bin/resolve?ApJL20401 ]
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Paper: astro-ph/0606628
Date: Mon, 26 Jun 2006 15:50:40 GMT (313kb)
Title: RApid Temporal Survey - RATS II: Followup observations of 4
newly discovered short period variables
Authors: Gavin Ramsay (1), Ralf Napiwotzki (2), Pasi Hakala (3), Harry
Lehto (3,4) ((1) MSSL/UCL, (2) Univ Hertfordshire, (3) Univ Turku (4)
NORDITA Copenhagen)
Comments: Accepted MNRAS 7 pages
The RApid Temporal Survey (RATS) is a survey to detect objects whose
optical intensity varies on timescales of less than ~70 min. In our
pilot dataset taken with the INT and the Wide Field Camera in Nov 2003
we discovered nearly 50 new variable objects. Many of these varied on
timescales much longer than 1 hr. However, only 4 objects showed a
modulation on a timescale of 1 hour or less. This paper presents
followup optical photometry and spectroscopy of these 4 objects. We
find that RAT J0455+1305 is a pulsating (on a period of 374 sec)
subdwarf B (sdB) star of the EC 14026 type. We have modelled its
spectrum and determine Teff = 29,200+/- 1900K and log g = 5.2+/-0.3
which locates it on the cool edge of the EC 14026 instability
strip. It has a modulation amplitude which is one of the highest of
any known EC 14026 star. Based on their spectra, photometric
variability and their infra-red colours, we find that RAT J0449+1756,
RAT J0455+1254 and RAT J0807+1510 are likely to be SX Phe stars -
dwarf Delta Sct stars. Our results show that our observing strategy is
a good method for finding rare pulsating stars.
( http://arXiv.org/abs/astro-ph/0606628 , 313kb)
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Paper: astro-ph/0606683
Date: Wed, 28 Jun 2006 10:55:02 GMT (324kb)
Title: How to calculate the CMB spectrum
Authors: Petter Callin
Comments: 18 pages, latex with revtex4, 16 postscript figures
We present a self-contained description of everything needed to write
a program that calculates the CMB power spectrum for the standard
model of cosmology (LCDM). This includes the equations used,
assumptions and approximations imposed on their solutions, and most
importantly the algorithms and programming tricks needed to make the
code actually work. The resulting program is compared to CMBFAST and
typically agrees to within 0.1% - 0.4%. It includes both helium,
reionization, neutrinos and the polarization power spectrum. The
methods presented here could serve as a starting point for people
wanting to write their own CMB program from scratch, for instance to
look at more exotic cosmological models where CMBFAST or the other
standard programs can't be used directly.
\\ ( http://arXiv.org/abs/astro-ph/0606683 , 324kb)
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First Results from the CHARA Array. VII. Long-Baseline Interferometric
Measurements of Vega Consistent with a Pole-On, Rapidly Rotating Star
J. P. Aufdenberg, A. Merand, V. Coude du Foresto, O. Absil, E. Di
Folco, P. Kervella, S. T. Ridgway, D. H. Berger, T. A. ten
Brummelaar, H. A. McAlister, J. Sturmann, L. Sturmann, and
N. H. Turner
Page 664 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ64436
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Hubble Space Telescope Identification of the Optical Counterparts of
Ultraluminous X-Ray Sources in M51
Yuichi Terashima, Hirohiko Inoue, and Andrew S. Wilson
Page 264 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ19634
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Paper: astro-ph/0607015
Date: Mon, 3 Jul 2006 04:29:30 GMT (368kb)
Title: Chemical Abundances in the Secondary Star of the Black Hole
Binary V4641 Sagittarii (SAX J1819.3-2525)
Authors: Kozo Sadakane (1), Akira Arai (1), Wako Aoki (2), Nobuo
Arimoto (2), Masahide Takada-Hidai (3), Takashi Ohnishi (4), Akito
Tajitsu (5), Timothy C. Beers (6), Nobuyuki Iwamoto (7), Nozomu
Tominaga (8), Hideyuki Umeda (8), Keiichi Maeda (8), and Ken'ichi
Nomoto (8) ((1) Osaka Kyoiku University, Japan, (2) NAOJ, Japan, (3)
Tokai University, Japan, (4) Nagoya Science Museum, Japan, (5) NAOJ,
HI, (6) Michigan State University, MI, (7) Japan Atomic Energy Agency,
Japan, (8) U. Tokyo, Japan)
Comments: 13 pages, 14 figures. Accepted for publication in the PASJ:
Publications of the Astronomical Society of Japan
We report on detailed spectroscopic studies performed for the
secondary star in the black hole binary (micro-quasar) V4641 Sgr in
order to examine its surface chemical composition and to see if its
surface shows any signature of pollution by ejecta from a supernova
explosion. High-resolution spectra of V4641 Sgr observed in the
quiescent state in the blue-visual region are compared with those of
the two bright well-studied B9 stars (14 Cyg and $\nu$ Cap) observed
with the same instrument. The effective temperature of V4641 Sgr
(10500 $\pm$ 200 K) is estimated from the strengths of He~{\sc i}
lines, while its rotational velocity, $\it v$ sin $\it i$ (95 $\pm$ 10
km s${}^{-1}$), is estimated from the profile of the Mg~{\sc ii} line
at 4481 \AA. We obtain abundances of 10 elements and find definite
over-abundances of N (by 0.8 dex or more) and Na (by 0.8 dex) in V4641
Sgr. From line-by-line comparisons of eight other elements (C, O, Mg,
Al, Si, Ti, Cr, and Fe) between V4641 Sgr and the two reference stars,
we conclude that there is no apparent difference in the abundances of
these elements between V4641 Sgr and the two normal late B-type stars,
which have been reported to have solar abundances. An evolutionary
model of a massive close binary system has been constructed to explain
the abundances observed in V4641 Sgr. The model suggests that the
progenitor of the black hole forming supernova was as massive as ~ 35
Msun on the main-sequence and, after becoming a ~ 10 Msun He star,
underwent "dark" explosion which ejected only N and Na-rich outer
layer of the He star without radioactive $^{56}$Ni.
( http://arXiv.org/abs/astro-ph/0607015 , 368kb)
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Paper: astro-ph/0607162
Date: Sat, 8 Jul 2006 17:00:04 GMT (271kb)
Title: Is there a caustic crossing in the lensed quasar Q2237+0305
observational data record?
Authors: R. Gil-Merino, J. Gonzalez-Cadelo, L.J. Goicoechea,
V.N. Shalyapin, G.F. Lewis
Comments: 5 pages, 3 figures, 3 tables, to appear in MNRAS
We re-investigate the gravitationally lensed system Q2237+0305 data
record to quantify the probability of having a caustic crossing in the
A component. Several works assume that this is the case, but no
quantitative analysis is available in the literature. We combine the
datasets from the OGLE and GLITP collaborations to accurately trace
the prominent event in the lightcurve for the A component of the
system. Then the observed event is compared with synthetic light
curves derived from trajectories in magnification maps. These maps are
generated using a ray-tracing technique. We take more than 10^9
trajectories and test a wide range of different physical properties of
the lensing galaxy and the source quasar (lens transverse velocity,
microlens mass, source intensity profile and source size). We found
that around 75% of our good trajectories (i.e. that are consistent
with the observations) are caustic crossings. In addition, a high
transverse velocity exceeding 300 km/s, a microlens mass of about 0.1
M_sun and a small standard accretion disk is the best parameter
combination. The results justify the interpretation of the OGLE-GLITP
event in Q2237+0305A as a caustic crossing. Moreover, the physical
properties of the lens and source are in very good agreement with
previous works. We also remark that a standard accretion disk is
prefered to those simpler approaches, and that the former should be
used in subsequent simulations.
\\ ( http://arXiv.org/abs/astro-ph/0607162 , 271kb)
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Paper: astro-ph/0607217
Date: Tue, 11 Jul 2006 08:34:56 GMT (230kb)
Title: Are peculiar Wolf-Rayet Stars of type WN8 Thorne-Zytkow
Objects?
Authors: C. Foellmi, A.F.J. Moffat
Comments: Published in PASP in 2002, but was missing in astro-ph
Journal-ref: Stellar Collisions, Mergers and their Consequences, ASP
Conference Proceedings, Vol. 263. Edited by Michael M. Shara. ISBN:
1-58381-103-6. San Francisco: Astronomical Society of the Pacific,
2002., p.123
Most population I Wolf-Rayet (WR) stars are the He-rich descendants of
the most massive stars (M_i = 25 - 100 M_sun). Evidence has been
accumulating over the years that among all pop I WR stars, those of
the relatively cool, N-rich subtype "WN8" are among the most peculiar:
1. They tend to be runaways, with large space velocity and/or avoid
clusters. 2. Unlike their equally luminous WN6,7 cousins, only a very
small number of WN8 stars are known to belong to a close binary with
an OB companion. 3. They are the systematically most highly
stochastically variable among all (single) WR stars. Taken together,
these suggest that many WN8 stars may originally have been in close
binaries (like half of all stars), in which the original primary
exploded as a supernova, leaving behind a very close binary containing
a massive star with a neutron star/black hole companion (like Cyg
X-3). When the massive remaining star evolved in turn, it engulfed and
eventually swallowed the compact companion, leading to the presently
puffed-up, variable WN8 star. Such stars could fall in the realm of
the exotic Thorne-Zytkow objects.
\\ ( http://arXiv.org/abs/astro-ph/0607217 , 230kb)
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Paper: astro-ph/0607399
Date: Mon, 17 Jul 2006 21:21:53 GMT (23kb)
Title: No Expanding Fireball: Resolving the Recurrent Nova RS Ophiuchi
with Infrared Interferometry
Authors: J.D. Monnier (1), R.K. Barry (2,12), W.A. Traub (7,8),
B.F. Lane (3), R.L. Akeson (6), S. Ragland (4), P.A. Schuller (7),
H.Le Coroller (11), J.P. Berger (5), R. Millan-Gabet (6), E. Pedretti
(1), F.P. Schloerb (9), C. Koresko (6), N.P. Carleton (7),
M.G. Lacasse (7), P. Kern (5), F. Malbet (5), K. Perraut (5),
M.J. Kuchner (12) and M.W. Muterspaugh (10) ((1) Michigan, (2)
Johns-Hopkins, (3) MIT, (4) Keck Obs., (5) Grenoble, (6) Michelson
Science Center, (7) CfA, (8) JPL, (9) UMass, (10) Caltech, (11)
Obs. de Haute-Provence, (12) NASA-GSFC)
Comments: Accepted by Astrophysical Journal Letters
Following the recent outburst of the recurrent nova RS Oph on 2006 Feb
12, we measured its near-infrared size using the IOTA, Keck, and PTI
Interferometers at multiple epochs. The characteristic size of ~3
milliarcseconds hardly changed over the first 60 days of the outburst,
ruling out currently-popular models whereby the near-infrared emission
arises from hot gas in the expanding shock. The emission was also
found to be significantly asymmetric, evidenced by non-zero closure
phases detected by IOTA. The physical interpretation of these data
depend strongly on the adopted distance to RS Oph. Our data can be
interpreted as the first direct detection of the underlying RS Oph
binary, lending support to the recent ``reborn red giant'' models of
Hachisu & Kato. However, this result hinges on an RS Oph distance of
~< 540 pc, in strong disagreement with the widely-adopted distance of
~1.6 kpc. At the farther distance, our observations imply instead the
existence of a non-expanding, dense and ionized circumbinary gaseous
disk or reservoir responsible for the bulk of the near-infrared
emission. Longer-baseline infrared interferometry is uniquely suited
to distinguish between these models and to ultimately determine the
distance, binary orbit, and component masses for RS Oph, one of the
closest-known (candidate) SNIa progenitor systems.
\\ ( http://arXiv.org/abs/astro-ph/0607399 , 23kb)
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Paper: astro-ph/0608407
Date: Sat, 19 Aug 2006 17:51:03 GMT (119kb)
Title: A direct empirical proof of the existence of dark matter
Authors: Douglas Clowe (1), Marusa Bradac (2), Anthony H. Gonzalez
(3), Maxim Markevitch (4), Scott W. Randall (4), Christine Jones (4),
and Dennis Zaritsky (1) ((1) Steward Observatory, Tucson, (2) KIPAC,
Stanford, (3) Department of Astronomy, Gainesville, (4) CfA,
Cambridge)
Comments: Accepted for publication in ApJL
We present new weak lensing observations of 1E0657-558 (z=0.296), a
unique cluster merger, that enable a direct detection of dark matter,
independent of assumptions regarding the nature of the gravitational
force law. Due to the collision of two clusters, the dissipationless
stellar component and the fluid-like X-ray emitting plasma are
spatially segregated. By using both wide-field ground based images and
HST/ACS images of the cluster cores, we create gravitational lensing
maps which show that the gravitational potential does not trace the
plasma distribution, the dominant baryonic mass component, but rather
approximately traces the distribution of galaxies. An 8-sigma
significance spatial offset of the center of the total mass from the
center of the baryonic mass peaks cannot be explained with an
alteration of the gravitational force law, and thus proves that the
majority of the matter in the system is unseen.
\\ ( http://arXiv.org/abs/astro-ph/0608407 , 119kb)
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Paper: astro-ph/0608638
Date: Tue, 29 Aug 2006 21:06:32 GMT (898kb)
Title: Some Pattern Recognition Challenges in Data-Intensive Astronomy
Authors: S.G. Djorgovski, C. Donalek, A. Mahabal, R. Williams,
A. Drake, M. Graham, E. Glikman
Comments: 8 pages, compressed pdf file, figures downgraded in quality
in order to match the arXiv size limit
Journal-ref: Proc. 18th International Conference on Pattern
Recognition (ICPR 2006), eds. Y.Y. Tang et al., IEEE Press, p. 856
(2006)
We review some of the recent developments and challenges posed by the
data analysis in modern digital sky surveys, which are representative
of the information-rich astronomy in the context of Virtual
Observatory. Illustrative examples include the problems of an
automated star-galaxy classification in complex and heterogeneous
panoramic imaging data sets, and an automated, iterative, dynamical
classification of transient events detected in synoptic sky
surveys. These problems offer good opportunities for productive
collaborations between astronomers and applied computer scientists and
statisticians, and are representative of the kind of challenges now
present in all data-intensive fields. We discuss briefly some emergent
types of scalable scientific data analysis systems with a broad
applicability.
\\ ( http://arXiv.org/abs/astro-ph/0608638 , 898kb)
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Propeller-driven Spectral State Transition in the Low-Mass X-Ray Binary 4U 1608-52
Xie Chen, Shuang Nan Zhang, and Guo Qiang Ding
Page 299 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ63924 ]
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Paper: astro-ph/0610407
Date: Fri, 13 Oct 2006 12:47:42 GMT (49kb)
Title: Radio recombination lines from the largest bound atoms in space
Authors: S. V. Stepkin (1), A. A. Konovalenko (1), N. G. Kantharia
(2), N. Udaya Shankar (3) ((1) Institute of Radio Astronomy, Kharkov,
Ukraine (2) National Centre for Radio Astrophysics (TIFR), Pune, India
(3) Raman Research Institute, Bangalore, India)
Comments: 5 pages, 4 figures, accepted for publication in MNRAS
In this paper, we report the detection of a series of radio
recombination lines (RRLs) in absorption near 26 MHz arising from the
largest bound carbon atoms detected in space. These atoms, which are
more than a million times larger than the ground state atoms are
undergoing delta transitions (n~1009, Delta n=4) in the cool tenuous
medium located in the Perseus arm in front of the supernova remnant,
Cassiopeia A. Theoretical estimates had shown that atoms which
recombined in tenuous media are stable up to quantum levels
n~1500. Our data indicates that we have detected radiation from atoms
in states very close to this theoretical limit. We also report high
signal-to-noise detections of alpha, beta and gamma transitions in
carbon atoms arising in the same clouds. In these data, we find that
the increase in line widths with quantum number (proportional to n^5)
due to pressure and radiation broadening of lines is much gentler than
expected from existing models which assume a power law background
radiation field. This discrepancy had also been noted earlier. The
model line widths had been overestimated since the turnover in
radiation field of Cassiopeia A at low frequencies had been
ignored. In this paper, we show that, once the spectral turnover is
included in the modeling, the slower increase in line width with
quantum number is naturally explained.
http://arXiv.org/abs/astro-ph/0610407
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Paper: astro-ph/0610422
Date: Fri, 13 Oct 2006 18:53:50 GMT (1026kb)
Title: Are High-Redshift Quasars Blurry?
Authors: Eric Steinbring
Comments: 8 pages, 5 figures, accepted for publication in the ApJ
It has been suggested that the fuzzy nature of spacetime at the Planck
scale may cause lightwaves to lose phase coherence, and if severe
enough this could blur images of distant point-like sources
sufficiently that they do not form an Airy pattern at the focal plane
of a telescope. Blurring this dramatic has already been
observationally ruled out by images from Hubble Space Telescope (HST),
but I show that the underlying phenomenon could still be stronger than
previously considered. It is harder to detect, which may explain why
it has gone unseen. A systematic search is made in archival HST images
of among the highest known redshift quasars. Planck-scale induced
blurring may be evident, but this could be confused with partially
resolved sources.
\\ ( http://arXiv.org/abs/astro-ph/0610422 , 1026kb)
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A Hubble Space Telescope Archival Survey of Feathers in Spiral
Galaxies
Misty A. La Vigne, Stuart N. Vogel, and Eve C. Ostriker
Page 818 [ http://www.journals.uchicago.edu/cgi-bin/resolve?ApJ65337
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Dynamics of the NGC4636 globular cluster system - An extremely dark
matter dominated galaxy?:
Y.Schuberth, T.Richtler, B.Dirsch, M.Hilker, S.S.Larsen,
M.Kissler-Patig and U.Mebold
A&A 459 (2006) 391-406 (Section 'Extragalactic astronomy')
http://publish.edpsciences.org/abstract/aa/v459/p391
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Paper: astro-ph/0610016
replaced with revised version Sat, 4 Nov 2006 19:15:46 GMT (419kb)
Title: The Fundamental Properties of Galaxies and a New Galaxy
Classification System
Authors: Christopher J. Conselice
Comments: MNRAS in press, 22 pages (some references and typos fixed)
\\ ( http://arXiv.org/abs/astro-ph/0610016 , 419kb)
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Paper: astro-ph/0611231
Date: Tue, 7 Nov 2006 18:21:40 GMT (603kb)
Title: Calibrating Type Ia Supernovae using the Planetary Nebula
Luminosity Function I. Initial Results
Authors: John J. Feldmeier, George H. Jacoby, Mark M. Phillips
Comments: 25 pages, 12 figures. Accepted for publication by the
Astrophysical Journal. Figures degraded to comply with limit. Full
paper is available at: http://www.as.ysu.edu/~jjfeldme/pnlf_Ia.pdf
We report the results of an [O III] lambda 5007 survey for planetary
nebulae (PN) in five galaxies that were hosts of well-observed Type Ia
supernovae: NGC 524, NGC 1316, NGC 1380, NGC 1448 and NGC 4526. The
goals of this survey are to better quantify the zero-point of the
maximum magnitude versus decline rate relation for supernovae Type Ia
and to validate the insensitivity of Type Ia luminosity to parent
stellar population using the host galaxy Hubble type as a
surrogate. We detected a total of 45 planetary nebulae candidates in
NGC 1316, 44 candidates in NGC 1380, and 94 candidates in NGC
4526. From these data, and the empirical planetary nebula luminosity
function (PNLF), we derive distances of 17.9 +0.8/-0.9 Mpc, 16.1
+0.8/-1.1 Mpc, and 13.6 +1.3/-1.2 Mpc respectively. Our derived
distance to NGC 4526 has a lower precision due to the likely presence
of Virgo intracluster planetary nebulae in the foreground of this
galaxy. In NGC 524 and NGC 1448 we detected no planetary nebulae
candidates down to the limiting magnitudes of our observations. We
present a formalism for setting realistic distance limits in these two
cases, and derive robust lower limits of 20.9 Mpc and 15.8 Mpc,
respectively.
After combining these results with other distances from the PNLF,
Cepheid, and Surface Brightness Fluctuations distance indicators, we
calibrate the optical and near-infrared relations for supernovae Type
Ia and we find that the Hubble constants derived from each of the
three methods are broadly consistent, implying that the properties of
supernovae Type Ia do not vary drastically as a function of stellar
population. We determine a preliminary Hubble constant of H_0 = 77 +/-
3 (random) +/- 5 (systematic) km/s/Mpc for the PNLF, though more
nearby galaxies with high-quality observations are clearly needed.
\\ ( http://arXiv.org/abs/astro-ph/0611231 , 603kb)
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Paper: astro-ph/0609161
replaced with revised version Tue, 7 Nov 2006 16:14:02 GMT (13kb)
Title: Astronomy with Small Telescopes
Authors: Bohdan Paczynski
Comments: 11 pages, accepted to PASP minor changes to the text
\\ ( http://arXiv.org/abs/astro-ph/0609161 , 13kb)
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Paper: astro-ph/0611647
Date: Tue, 21 Nov 2006 00:49:45 GMT (46kb)
Title: Gamma rays from colliding winds of massive stars
Authors: Anita Reimer, Olaf Reimer, Martin Pohl
Comments: Comments: 6 pages, 5 figures, Accepted for publication in
Astrophysics and Space Science, Proc. of "The Multi-Messenger Approach
to High-Energy Gamma-ray Sources (Third Workshop on the Nature of
Unidentified High-Energy Sources)", Barcelona, July 4-7, 2006
Colliding winds of massive binaries have long been considered as
potential sites of non-thermal high-energy photon production. This is
motivated by the detection of non-thermal spectra in the radio band,
as well as by correlation studies of yet unidentified EGRET gamma-ray
sources with source populations appearing in star formation
regions. This work re-considers the basic radiative processes and its
properties that lead to high energy photon production in long-period
massive star systems. We show that Klein-Nishina effects as well as
the anisotropic nature of the inverse Compton scattering, the
dominating leptonic emission process, likely yield spectral and
variability signatures in the gamma-ray domain at or above the
sensitivity of current or upcoming gamma ray instruments like
GLAST-LAT. In addition to all relevant radiative losses, we include
propagation (such as convection in the stellar wind) as well as photon
absorption effects, which a priori can not be neglected. The
calculations are applied to WR140 and WR147, and predictions for their
detectability in the gamma-ray regime are provided. Physically similar
specimen of their kind like WR146, WR137, WR138, WR112 and WR125 may
be regarded as candidate sources at GeV energies for near-future
gamma-ray experiments. Finally, we discuss several aspects relevant
for eventually identifying this source class as a gamma-ray emitting
population. Thereby we utilize our findings on the expected radiative
behavior of typical colliding wind binaries in the gamma-ray regime as
well as its expected spatial distribution on the gamma-ray sky.
\\ ( http://arXiv.org/abs/astro-ph/0611647 , 46kb)
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Paper: astro-ph/0611646
Date: Mon, 20 Nov 2006 22:06:37 GMT (1581kb)
Title: XMM-Newton observations of HESS J1813-178 reveal a composite
Supernova remnant
Authors: S. Funk, J. A. Hinton, Y. Moriguchi, F. A. Aharonian,
Y. Fukui, W. Hofmann, D. Horns, G. Puehlhofer, O. Reimer, G. Rowell,
R. Terrier, J. Vink, S. Wagner
Comments: Submitted to A&A
We present X-ray and 12CO(J=1-0) observations of the very-high-energy
(VHE) gamma-ray source HESS J1813-178 with the aim of understanding
the origin of the gamma-ray emission. Using this dataset we are able
to undertake spectral and morphological studies of the X-ray emission
from this object with greater precision than previous studies. NANTEN
12CO(J=1-0) data are used to search for correlations of the gamma-ray
emission with molecular clouds which could act as target material for
gamma-ray production in a hadronic scenario. The NANTEN 12CO(J=1-0)
observations show a giant molecular cloud of mass 2.5 10^5 M$_{\sun}$
at a distance of 4 kpc in the vicinity of HESS J1813-178. Even though
there is no direct positional coincidence, this giant cloud might have
influenced the evolution of the gamma-ray source and its
surroundings. The X-ray data show a highly absorbed non-thermal X-ray
emitting object coincident with the previously known ASCA source AX
J1813-178 showing a compact core and an extended tail towards the
north-east, located in the centre of the radio shell-type Supernova
remnant (SNR) G12.82-0.2. This central object shows morphological and
spectral resemblance to a Pulsar Wind Nebula (PWN) and we therefore
consider that the object is very likely to be a composite SNR. We
discuss the scenario in which the gamma-rays originate in the shell of
the SNR and the one in which they originate in the central object. We
demonstrate, that in order to connect the core X-ray emission to the
VHE gamma-ray emission electrons have to be accelerated to energies of
at least 1 PeV.
\\ ( http://arXiv.org/abs/astro-ph/0611646 , 1581kb)
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Paper: astro-ph/0612285
Date: Mon, 11 Dec 2006 19:49:59 GMT (781kb)
Title: The Hubble Diagram to Redshift >6 from 69 Gamma-Ray Bursts
Authors: Bradley E. Schaefer
Categories: astro-ph
Comments: ApJ in press, 88 pages, 15 figures
One of the few ways to measure the properties of Dark Energy is to
extend the Hubble daigram (HD) to higher redshifts with Gamma-Ray
Bursts (GRBs). GRBs have at least five properties (their spectral lag,
variability, spectral peak photon energy, time of the jet break, and
the minimum rise time) which have correlations to the luminosity of
varying quality. In this paper, I construct a GRB HD with 69 GRBs over
a redshift range of 0.17 to >6, with half the bursts having a redshift
larger than 1.7. This paper uses over 3.6 times as many GRBs and 12.7
times as many luminosity indicators as any previous GRB HD work. For
the gravitational lensing and Malmquist biases, I find that the biases
are small, with an average of 0.03 mag and an RMS scatter of 0.14 mag
in the distance modulus. The GRB HD is well-behaved and nicely
delineates the shape of the HD. The reduced chi-square for the fit to
the concordance model is 1.05 and the RMS scatter about the
concordance model is 0.65 mag. This accuracy is just a factor of 2.0
times that gotten for the same measure from all the big supernova
surveys. I fit the GRB HD to a variety of models, including where the
Dark Energy has its equation of state parameter varying as w(z)=w_0 +
w_a z/(1+z). I find that the concordance model is consistent with the
data. That is, the Dark Energy can be described well as a Cosmological
Constant that does not change with time. (abridged)
\\ ( http://arXiv.org/abs/astro-ph/0612285 , 781kb)
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Intergalactic medium heating by dark matter
E. Ripamonti, M. Mapelli, A. Ferrara
Monthly Notices of the Royal Astronomical Society; Volume 374, Issue
3, 2007 Jan 1, Page 1067
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2966.2006.11222.x?ai=rs&
ui=alp8&af=T
------------------------------------------------------------------------
Paper: astro-ph/0703125
Date: Wed, 7 Mar 2007 17:25:15 GMT (225kb)
Title: Discovery of a Very Bright, Nearby Gravitational Microlensing
Event
Authors: B. Scott Gaudi, Joseph Patterson, David S. Spiegel, Thomas
Krajci, R. Koff, G. Pojmanski, Subo Dong, Andrew Gould, Jose
L. Prieto, Cullen H. Blake, Peter W. A. Roming, David P. Bennett,
Joshua S. Bloom, David Boyd, Pierre de Ponthiere, N. Mirabal,
Christopher W. Morgan, Ronald R. Remillard, T. Vanmunster, R. Mark
Wagner, Linda C. Watson
Categories: astro-ph
Comments: Submitted to ApJ, 9 pages, 5 figures. Data available upon
request
We report the serendipitous detection of a very bright, very nearby
microlensing event. In late October 2006, an otherwise unremarkable A0
star at a distance ~1 kpc (GSC 3656-1328) brightened achromatically by
a factor of nearly 40 over the span of several days and then decayed
in an apparently symmetrical way. We present a light curve of the
event based on optical photometry from the Center for Backyard
Astrophysics and the All Sky Automatic Survey, as well as
near-infrared photometry from the Peters Automated Infrared Imaging
Telescope. This light curve is well-fit by a generic microlensing
model. We also report optical spectra, and Swift X-ray and UV
observations that are consistent with the microlensing
interpretation. We discuss and reject alternative explanations for
this variability. The lens star is probably a low-mass star or brown
dwarf, with a relatively high proper motion of >20 mas/yr, and may be
visible using precise optical/infrared imaging taken several years
from now. We demonstrate that a modest, all-sky survey telescope could
detect ~10 such events per year, which would enable searches for very
low-mass planetary companions to relatively nearby stars.
\\ ( http://arXiv.org/abs/astro-ph/0703125 , 225kb)
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Paper: astro-ph/0703143
Date: Wed, 7 Mar 2007 12:02:22 GMT (314kb)
Title: On the difference between Herbig Ae and Herbig Be stars
Authors: J.C. Mottram, J.S. Vink, R.D. Oudmaijer, M. Patel
Categories: astro-ph
We present linear spectropolarimetric data for eight Herbig Be and
four Herbig Ae stars at H alpha, H beta and H gamma. Changes in the
linear polarisation are detected across all Balmer lines for a large
fraction of the observed objects, confirming that the small-scale
regions surrounding these objects are flattened
(i.e. disk-like). Furthermore, all objects with detections show
similar characteristics at the three spectral lines, despite
differences in transition probability and optical depth going from H
alpha to H gamma. A large fraction of early Herbig Be stars (B0-B3)
observed show line depolarisation effects. However the early Herbig Ae
stars (A0-A2), observed for comparison, show intrinsic line
polarisation signatures. Our data suggest that the popular magnetic
accretion scenario for T Tauri objects may be extended to Herbig Ae
stars, but that it may not be extended to early Herbig Be stars, for
which the available data are consistent with disc accretion.
\\ ( http://arXiv.org/abs/astro-ph/0703143 , 314kb)
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arXiv:0704.0460
Date: Tue, 3 Apr 2007 20:43:52 GMT (622kb)
Title: The Kilodegree Extremely Little Telescope (KELT): A Small
Robotic Telescope for Large-Area Synoptic Surveys
Authors: Joshua Pepper (1), Richard W. Pogge (1), D. L. DePoy (1),
J. L. Marshall (1), K. Z. Stanek (1), Amelia M. Stutz (2), Shawn
Poindexter (1), Robert Siverd (1), Thomas P. O'Brien (1), Mark
Trueblood (3), Patricia Trueblood (3) ((1) The Ohio State University
Department of Astronomy, (2) University of Arizona Department of
Astronomy, (3) Winer Observatory)
Categories: astro-ph
Comments: 31 pages, 13 figures; submitted to AJ
The Kilodegree Extremely Little Telescope (KELT) project is a survey
for planetary transits of bright stars. It consists of a
small-aperture, wide-field automated telescope located at Winer
Observatory near Sonoita, Arizona. The telescope surveys a set of 26 x
26 degree fields, together covering about 25% of the Northern sky,
targeting stars in the range of 8 10^8 M_sun must be assembled to recollect all components of the
swept-up mass.
\\ ( http://arxiv.org/abs/0705.3048 , 552kb)
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arXiv:0705.3054
Date: Mon, 21 May 2007 20:44:42 GMT (1074kb)
Title: And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and
the Waists of Bipolar Nebulae
Authors: Nathan Smith, John Bally, and Josh Walawender
Categories: astro-ph
Comments: AJ accepted, 27 pages
We report the discovery of two new circumstellar ring nebulae in the western
Carina Nebula. The brighter object, SBW1, resembles a lidless staring eye and
encircles a B1.5 Iab supergiant. Its size is identical to the inner ring around
SN1987A, but SBW1's low N abundance indicates that the star didn't pass through
a RSG phase. The fainter object, SBW2, is a more distorted ring, is N-rich, and
has a central star that seems to be invisible. We discuss these two new nebulae
in context with rings around SN1987A, Sher25, HD168625, RY Scuti, WeBo1, SuWt2,
and others. The ring bearers fall into two groups: Five rings surround hot
supergiants, and all except for the one known binary are carbon copies of the
ring around SN1987A. We propose a link between these rings and B[e] supergiants,
where the rings derive from the same material in an earlier B[e] phase. The
remaining four rings surround evolved intermediate-mass stars; all members of
this ring fellowship are close binaries, hinting that binary interactions govern
the forging of such rings. We estimate that there may be several thousand more
dark rings in the Galaxy, but we are scarcely aware of their existence due to
selection effects. The lower-mass objects might be the equatorial density
enhancements often invoked to bind the waists of bipolar PNe.
\\ ( http://arxiv.org/abs/0705.3054 , 1074kb)
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arXiv:0706.0569
Date: Tue, 5 Jun 2007 02:12:10 GMT (572kb)
Title: The Extraordinary Infrared Spectrum of NGC 1222 (Mkn 603)
Authors: Sara C. Beck (Tel Aviv) and Jean L. Turner (UCLA)
Categories: astro-ph
Comments: accepted, Astronomical Journal. 29 pp, 4 figures
\\
The infrared spectra of starburst galaxies are dominated by the
low-excitation lines of [NeII] and [SIII], and the stellar populations deduced
from these spectra appear to lack stars larger than about 35 Msun. The only
exceptions to this result until now were low metallicity dwarf galaxies. We
report our analysis of the mid-infrared spectra obtained with IRS on Spitzer of
the starburst galaxy NGC 1222 (Mkn 603). NGC 1222 is a large spheroidal galaxy
with a starburst nucleus that is a compact radio and infrared source, and its
infrared emission is dominated by the [NeIII] line. This is the first starburst
of solar or near-solar metallicity, known to us, which is dominated by the
high-excitation lines and which is a likely host of high mass stars. We model
the emission with several different assumptions as to the spatial distibution
of the high- and low-excitation lines and find that the upper mass cutoff in
this galaxy is 40-100 Msun.
\\ ( http://arxiv.org/abs/0706.0569 , 572kb)
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ULTRACAM: an ultrafast, triple-beam CCD camera for high-speed
astrophysics
V. S. Dhillon, T. R. Marsh, M. J. Stevenson, D. C. Atkinson, P. Kerry,
P. T. Peacocke, A. J. A. Vick, S. M. Beard, D. J. Ives, D. W. Lunney, S.
A. McLay, C. J. Tierney, J. Kelly, S. P. Littlefair, R. Nicholson, R.
Pashley, E. T. Harlaftis, K. O'Brien
Page 825
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2966.2007.11881.x?ai=rs&ui=alp8&af=T
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arXiv:0707.2382
Date: Mon, 16 Jul 2007 20:03:30 GMT (941kb)
Title: Evidence for a Long-Standing Top-Heavy IMF in the Central Parsec of the
Galaxy
Authors: H. Maness, F. Martins, S. Trippe, R. Genzel, J. R. Graham, C. Sheehy,
M. Salaris, S. Gillessen, T. Alexander, T. Paumard, T. Ott, R. Abuter, and F.
Eisenhauer
Categories: astro-ph
Comments: 18 pages, 10 figures, Accepted to ApJ: 15 July 2007
We classify 329 late-type giants within 1 parsec of Sgr A*, using the
adaptive optics integral field spectrometer SINFONI on the VLT. These
observations represent the deepest spectroscopic data set so far obtained for
the Galactic Center, reaching a 50% completeness threshold at the approximate
magnitude of the helium-burning red clump (Ks ~ 15.5 mag.). Combining our
spectroscopic results with NaCo H and Ks photometry, we construct an observed
Hertzsprung-Russell diagram, which we quantitatively compare to theoretical
distributions of various star formation histories of the inner Galaxy, using a
chi-squared analysis. Our best-fit model corresponds to continuous star
formation over the last 12 Gyr with a top-heavy initial mass function (IMF).
The similarity of this IMF to the IMF observed for the most recent epoch of
star formation is intriguing and perhaps suggests a connection between recent
star formation and the stars formed throughout the history of the Galactic
Center.
\\ ( http://arxiv.org/abs/0707.2382 , 941kb)
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arXiv:0707.3639
Date: Tue, 24 Jul 2007 20:19:54 GMT (172kb)
Title: The Minimum Amount of Stars a Galaxy Will Form
Authors: Bradley E. Warren, Helmut Jerjen, and B\"arbel S. Koribalski
Categories: astro-ph
Comments: 37 Pages, 7 Figures. Accepted for publication in AJ
We present an analysis of the atomic hydrogen and stellar properties of 38
late-type galaxies in the local Universe covering a wide range of HI
mass-to-light ratios (M_HI/L_B), stellar luminosities, and surface
brightnesses. From these data we have identified an upper envelope for the
M_HI/L_B as a function of galaxy luminosity. This implies an empirical relation
between the minimum amount of stars a galaxy will form and its initial baryonic
mass. While the stellar mass of a galaxy seems to be only loosely connected to
its baryonic mass, the latter quantity is strongly linked to the galaxy's
dynamical mass as it is observed in the baryonic Tully-Fisher relation. We find
that dwarf irregular galaxies with generally high M_HI/L_B-ratios follow the
same trend as defined by lower M_HI/L_B giant galaxies, but are underluminous
for their rotation velocity to follow the trend in a stellar mass Tully-Fisher
relation, suggesting that the baryonic mass of the dwarf galaxies is normal but
they have failed to produced a sufficient amount of stars. Finally, we present
a three dimensional equivalent to the morphology-density relation which shows
that high M_HI/L_B galaxies preferentially evolve and/or survive in low-density
environments. We conclude that an isolated galaxy with a shallow dark matter
potential can retain a large portion of its baryonic matter in the form of gas,
only producing a minimum quantity of stars necessary to maintain a stable gas
disk.
\\ ( http://arxiv.org/abs/0707.3639 , 172kb)
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arXiv:0708.3135
Date: Thu, 23 Aug 2007 14:03:25 GMT (1344kb)
Title: Mid-Infrared Instrumentation for the European Extremely Large Telescope
Authors: S. Kendrew (1), B. Brandl (1), R. Lenzen (2), L. Venema (3), H.U.
K\"aufl (4), G. Finger (4), A. Glasse (5), R. Stuik (1) ((1) Leiden
University, (2) MPIA, Heidelberg, (3) Astron, Dwingeloo, (4) ESO, Garching,
(5) UK Astronomy Technology Centre, Edinburgh)
Categories: astro-ph
Comments: for publication in SPIE Proceedings vol. 6692, Cryogenic Optical
Systems and Instrumentation XII, eds. J.B. Heaney and L.G. Burriesci, San
Diego, Aug 2007
MIDIR is the proposed thermal/mid-IR imager and spectrograph for the European
Extremely Large Telescope (E-ELT). It will cover the wavelength range of 3 to
at least 20 microns. Designed for diffraction-limited performance over the
entire wavelength range, MIDIR will require an adaptive optics system; a
cryogenically cooled system could offer optimal performance in the IR, and this
is a critical aspect of the instrument design. We present here an overview of
the project, including a discussion of MIDIR's science goals and a comparison
with other infrared (IR) facilities planned in the next decade; top level
requirements derived from these goals are outlined. We describe the optical and
mechanical design work carried out in the context of a conceptual design study,
and discuss some important issues to emerge from this work, related to the
design, operation and calibration of the instrument. The impact of telescope
optical design choices on the requirements for the MIDIR instrument is
demonstrated.
\\ ( http://arxiv.org/abs/0708.3135 , 1344kb)
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arXiv:0709.2563
Date: Mon, 17 Sep 2007 09:27:15 GMT (270kb)
Title: Nulling interferometry: performance comparison between Antarctica and
other ground-based sites
Authors: O. Absil, V. Coude du Foresto, M. Barillot, M. R. Swain
Categories: astro-ph
Comments: 10 pages, accepted for publication in A&A
Detecting the presence of circumstellar dust around nearby solar-type main
sequence stars is an important pre-requisite for the design of future
life-finding space missions such as ESA's Darwin or NASA's Terrestrial Planet
Finder (TPF). The high Antarctic plateau may provide appropriate conditions to
perform such a survey from the ground. We investigate the performance of a
nulling interferometer optimised for the detection of exozodiacal discs at Dome
C, on the high Antarctic plateau, and compare it to the expected performance of
similar instruments at temperate sites. Based on the currently available
measurements of the turbulence characteristics at Dome C, we adapt the GENIEsim
software (Absil et al. 2006, A&A 448) to simulate the performance of a nulling
interferometer on the high Antarctic plateau. To feed a realistic instrumental
configuration into the simulator, we propose a conceptual design for ALADDIN,
the Antarctic L-band Astrophysics Discovery Demonstrator for Interferometric
Nulling. We assume that this instrument can be placed above the 30-m high
boundary layer, where most of the atmospheric turbulence originates. We show
that an optimised nulling interferometer operating on a pair of 1-m class
telescopes located 30 m above the ground could achieve a better sensitivity
than a similar instrument working with two 8-m class telescopes at a temperate
site such as Cerro Paranal. The detection of circumstellar discs about 20 times
as dense as our local zodiacal cloud seems within reach for typical Darwin/TPF
targets in a integration time of a few hours. Moreover, the exceptional
turbulence conditions significantly relax the requirements on real-time control
loops, which has favourable consequences on the feasibility of the nulling
instrument.
( http://arxiv.org/abs/0709.2563 , 270kb)
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arXiv:0710.3166
Date: Tue, 16 Oct 2007 20:04:09 GMT (37kb)
Title: Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen
in Nebular Spectra
Authors: Douglas C. Leonard
Categories: astro-ph
Comments: Accepted for publication in The Astrophysical Journal. 16 pages, 1
figure
\\
Despite intense scrutiny, the progenitor system(s) that gives rise to Type Ia
supernovae remains unknown. The favored theory invokes a carbon-oxygen white
dwarf accreting hydrogen-rich material from a close companion until a
thermonuclear runaway ensues that incinerates the white dwarf. However,
simulations resulting from this single-degenerate, binary channel demand the
presence of low-velocity H-alpha emission in spectra taken during the late
nebular phase, since a portion of the companion's envelope becomes entrained in
the ejecta. This hydrogen has never been detected, but has only rarely been
sought. Here we present results from a campaign to obtain deep, nebular-phase
spectroscopy of nearby Type Ia supernovae, and include multi-epoch observations
of two events: SN 2005am (slightly subluminous) and SN 2005cf (normally
bright). No H-alpha emission is detected in the spectra of either object. An
upper limit of 0.01 M_Sun of solar abundance material in the ejecta is
established from the models of Mattila et al. which, when coupled with the
mass-stripping simulations of Marietta et al. and Meng et al. effectively rules
out progenitor systems for these supernovae with secondaries close enough to
the white dwarf to be experiencing Roche lobe overflow at the time of
explosion. Alternative explanations for the absence of H-alpha emission, along
with suggestions for future investigations necessary to confidently exclude
them as possibilities, are critically evaluated.
\\ ( http://arxiv.org/abs/0710.3166 , 37kb)
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The dark nature of GRB 051022 and its host galaxy:
A. J. Castro-Tirado et al.
A&A 475 (2007) 101-107 (Section 'Cosmology (including clusters of galaxies)')
http://www.aanda.org/10.1051/0004-6361:20066748
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arXiv:0711.1495
Date: Fri, 9 Nov 2007 16:08:48 GMT (323kb)
Title: V838 Monocerotis: A Geometric Distance from Hubble Space Telescope
Polarimetric Imaging of its Light Echo
Authors: William B. Sparks (1), Howard E. Bond (1), Misty Cracraft (1), Zolt
Levay (1), Lisa A. Crause (2), Michael A. Dopita (3), Arne A. Henden (4),
Ulisse Munari (5), Nino Panagia (1,6), Sumner G. Starrfield (7), Ben E.
Sugerman (8), R. Mark Wagner (9), and Richard L. White (1), (1-Space
Telescope Science Institute, 2-South African Astronomical Observatory,
3-RSAA, Australian National University, 4-AAVSO, 5-INAF Osservatorio
Astronomico di Padova, 6-INAF Osservatorio Astrofisico di Catania and
Supernova Ltd., 7-Arizona State University, 8-Goucher College, 9-Large
Binocular Telescope Observatory)
Categories: astro-ph
Comments: 43 pages, 17 figures, 3 tables; accepted for publication in the
Astronomical Journal
Report-no: STScI E-print #1785
Following the outburst of the unusual variable star V838 Monocerotis in 2002,
a spectacular light echo appeared. A light echo provides the possibility of
direct geometric distance determination, because it should contain a ring of
highly linearly polarized light at a linear radius of ct, where t is the time
since the outburst. We present imaging polarimetry of the V838 Mon light echo,
obtained in 2002 and 2005 with the Advanced Camera for Surveys onboard the
Hubble Space Telescope, which confirms the presence of the highly polarized
ring. Based on detailed modeling that takes into account the outburst light
curve, the paraboloidal echo geometry, and the physics of dust scattering and
polarization, we find a distance of 6.1+-0.6 kpc. The error is dominated by the
systematic uncertainty in the scattering angle of maximum linear polarization,
taken to be theta_{max}=90^o +- 5^o. The polarimetric distance agrees
remarkably well with a distance of 6.2+-1.5 kpc obtained from the entirely
independent method of main-sequence fitting to a sparse star cluster associated
with V838 Mon. At this distance, V838 Mon at maximum light had M_V\simeq-9.8,
making it temporarily one of the most luminous stars in the Local Group. Our
validation of the polarimetric method offers promise for measurement of
extragalactic distances using supernova light echoes.
\\ ( http://arxiv.org/abs/0711.1495 , 323kb)
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Exploring the Variable Sky with the Sloan Digital Sky Survey
Branimir Sesar, Zeljko Ivezic, Robert H. Lupton, Mario Juric, James E. Gunn,
Gillian
R. Knapp, Nathan De Lee, J. Allyn Smith, Gajus Miknaitis, Huan Lin, Douglas
Tucker,
Mamoru Doi, Masayuki Tanaka, Masataka Fukugita, Jon Holtzman, Steve Kent, Brian
Yanny, David Schlegel, Douglas Finkbeiner, Nikhil Padmanabhan, Constance
M. Rockosi,
Nicholas Bond, Brian Lee, Chris Stoughton, Sebastian Jester, Hugh Harris, Paul
Harding, Jon Brinkmann, Donald P. Schneider, Donald York, Michael W. Richmond,
and
Daniel Vanden Berk
Page 2236 [ http://www.journals.uchicago.edu/cgi-bin/resolve?AJ205861 ]
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Population III stars: hidden or disappeared?
Luca Tornatore, Andrea Ferrara, Raffaella Schneider
Page 945
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2966.2007.12215.x?ai=rs&ui=alp8&af=T
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arXiv:0712.4335
Date: Fri, 28 Dec 2007 11:24:16 GMT (1377kb)
Title: The stability of spectroscopic instruments: A unified Allan variance
computation scheme
Authors: Volker Ossenkopf
Categories: astro-ph
Comments: accepted for publication in Astronomy & Astrophysics
\\
The Allan variance is a standard technique to characterise the stability of
spectroscopic instruments used in astronomical observations. The period for
switching between source and reference measurement is often derived from the
Allan minimum time.
We propose a new approach for the computation of the Allan variance of
spectrometer data combining the advantages of the two existing methods into a
unified scheme. Using the Allan variance spectrum we derive the optimum
strategy for symmetric observing schemes minimising the total uncertainty of
the data resulting from radiometric and drift noise.
The unified Allan variance computation scheme is designed to trace
total-power and spectroscopic fluctuations within the same framework. The
method includes an explicit error estimate both for the individual Allan
variance spectra and for the derived stability time. A new definition of the
instrument stability time allows to characterise the instrument even in the
case of a fluctuation spectrum shallower than 1/f, as measured for the total
power fluctuations in high-electron-mobility transistors. We find a non-linear
impact of the binning of spectrometer channels on the resulting noise and the
Allan time deviating from the description in existing theoretical treatments.
\\ ( http://arxiv.org/abs/0712.4335 , 1377kb)
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The 3D skeleton: tracing the filamentary structure of the Universe
T. Sousbie, C. Pichon, S. Colombi, D. Novikov, D. Pogosyan
Page 1655
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2966.2007.12685.x?ai=rs&ui=alp8&af=T
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arXiv:0801.2120
Date: Mon, 14 Jan 2008 17:27:49 GMT (721kb)
Title: Galactic kinematics with RAVE data: I. The distribution of stars towards
the Galactic poles
Authors: L. Veltz, O. Bienaym\'e, K. C. Freeman, J. Binney, J. Bland-Hawthorn,
B. K. Gibson, G. Gilmore, E. K. Grebel, A. Helmi, U. Munari, J. F. Navarro,
Q. A. Parker, G. M. Seabroke, A. Siebert, M. Steinmetz, F. G. Watson, M.
Williams, R. F. G. Wyse and T. Zwitter
Categories: astro-ph
Comments: 15 pages, 13 EPS figures and 1 table
\\
We analyze the distribution of G and K type stars towards the Galactic poles
using RAVE and ELODIE radial velocities, 2MASS photometric star counts, and
UCAC2 proper motions. The combination of photometric and 3D kinematic data
allows us to disentangle and describe the vertical distribution of dwarfs,
sub-giants and giants and their kinematics. We identify discontinuities within
the kinematics and magnitude counts that separate the thin disk, thick disk and
a hotter component. The respective scale heights of the thin disk and thick
disk are 225$\pm$10 pc and 1048$\pm$36 pc. We also constrain the luminosity
function and the kinematic distribution function. The existence of a kinematic
gap between the thin and thick disks is incompatible with the thick disk having
formed from the thin disk by a continuous process, such as scattering of stars
by spiral arms or molecular clouds. Other mechanisms of formation of the thick
disk such as `created on the spot' or smoothly `accreted' remain compatible
with our findings.
\\ ( http://arxiv.org/abs/0801.2120 , 721kb)
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arXiv:0801.2371
Date: Tue, 15 Jan 2008 20:29:08 GMT (425kb)
Title: CLOUDS search for variability in brown dwarf atmospheres
Authors: B. Goldman (NMSU, MPIA), M. C. Cushing (UA), M. S. Marley (Ames), \'E.
Artigau (Gemini), K. S. Baliyan (PRL), V. J. S. B\'ejar (IAC), J. A.
Caballero (MPIA, IAC), N. Chanover (NMSU), M. Connelley (IfA), R. Doyon
(Montr\'eal), T. Forveille (CFHT, Grenoble), S. Ganesh (PRL), C. R. Gelino
(NMSU, Spitzer), H. B. Hammel (SSI), J. Holtzman (NMSU), S. Joshi (ARIES), U.
C. Joshi (PRL), S. K. Leggett (JAC), M. C. Liu (IfA), E. L. Mart\'in (IAC),
V. Mohan (IUCAA), D. Nadeau (Montr\'eal), R. Sagar (AIRES) and D. Stephens
(BYU), for the CLOUDS Collaboration
Categories: astro-ph
Comments: 17 pages, 14 figures, accepted by A&A
\\
Context: L-type ultra-cool dwarfs and brown dwarfs have cloudy atmospheres
that could host weather-like phenomena. The detection of photometric or
spectral variability would provide insight into unresolved atmospheric
heterogeneities, such as holes in a global cloud deck.
Aims: It has been proposed that growth of heterogeneities in the global cloud
deck may account for the L- to T-type transition as brown dwarf photospheres
evolve from cloudy to clear conditions. Such a mechanism is compatible with
variability. We searched for variability in the spectra of five L6 to T6 brown
dwarfs in order to test this hypothesis.
Methods: We obtained spectroscopic time series using VLT/ISAAC, over
0.99-1.13um, and IRTF/SpeX for two of our targets, in J, H and K bands. We
search for statistically variable lines and correlation between those.
Results: High spectral-frequency variations are seen in some objects, but
these detections are marginal and need to be confirmed. We find no evidence for
large amplitude variations in spectral morphology and we place firm upper
limits of 2 to 3% on broad-band variability, on the time scale of a few hours.
The T2 transition brown dwarf SDSS J1254-0122 shows numerous variable features,
but a secure variability diagnosis would require further observations.
Conclusions: Assuming that any variability arises from the rotation of
patterns of large-scale clear and cloudy regions across the surface, we find
that the typical physical scale of cloud cover disruption should be smaller
than 5-8% of the disk area for four of our targets. The possible variations
seen in SDSS J1254-0122 are not strong enough to allow us to confirm the cloud
breaking hypothesis.
\\ ( http://arxiv.org/abs/0801.2371 , 425kb)
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arXiv:0801.4031
Date: Fri, 25 Jan 2008 21:13:29 GMT (34kb)
Title: Distant future of the Sun and Earth revisited
Authors: Klaus-Peter Schroder and Robert C. Smith
Categories: astro-ph
Comments: MNRAS 2008, in print (accepted Jan. 23rd, 2008)
We revisit the distant future of the Sun and the solar system, based on
stellar models computed with a thoroughly tested evolution code. For the solar
giant stages, mass-loss by the cool (but not dust-driven) wind is considered in
detail. Using the new and well-calibrated mass-loss formula of Schroder & Cuntz
(2005, 2007), we find that the mass lost by the Sun as an RGB giant (0.332
M_Sun, 7.59 Gy from now) potentially gives planet Earth a significant orbital
expansion, inversely proportional to the remaining solar mass.
According to these solar evolution models, the closest encounter of planet
Earth with the solar cool giant photosphere will occur during the tip-RGB
phase. During this critical episode, for each time-step of the evolution model,
we consider the loss of orbital angular momentum suffered by planet Earth from
tidal interaction with the giant Sun, as well as dynamical drag in the lower
chromosphere. We find that planet Earth will not be able to escape engulfment,
despite the positive effect of solar mass-loss. In order to survive the solar
tip-RGB phase, any hypothetical planet would require a present-day minimum
orbital radius of about 1.15 AU.
Furthermore, our solar evolution models with detailed mass-loss description
predict that the resulting tip-AGB giant will not reach its tip-RGB size. The
main reason is the more significant amount of mass lost already in the RGB
phase of the Sun. Hence, the tip-AGB luminosity will come short of driving a
final, dust-driven superwind, and there will be no regular solar planetary
nebula (PN). But a last thermal pulse may produce a circumstellar (CS) shell
similar to, but rather smaller than, that of the peculiar PN IC 2149 with an
estimated total CS shell mass of just a few hundredths of a solar mass.
\\ ( http://arxiv.org/abs/0801.4031 , 34kb)
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arXiv:0802.0481
Date: Mon, 4 Feb 2008 19:36:22 GMT (541kb)
Title: Confirmation of a Faraday Rotation Measure Anomaly in Cygnus
Authors: Catherine A. Whiting, Steven R. Spangler, Laura D. Ingleby, L. Matthew
Haffner
Categories: astro-ph
Comments: Submitted to the Astrophysical Journal
License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
We confirm the reality of a reversal of the sign of the Faraday Rotation
Measure in the Galactic plane in Cygnus (Lazio et al, 1990), possibly
associated with the Cygnus OB1 association. The rotation measure changes by
several hundred rad/m$^2$ over an angular scale of $2-5^{\circ}$. We show that
a simple model of an expanding plasma shell with an enhanced density and
magnetic field, consistent with observations of H$\alpha$ emission in this part
of sky, and physically associated with a superbubble of the Cygnus OB1
association, can account for the magnitude and angular scale of this feature.
\\ ( http://arxiv.org/abs/0802.0481 , 541kb)
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arXiv:0802.0702 (*cross-listing*)
Date: Tue, 5 Feb 2008 21:27:40 GMT (134kb)
Title: Strategies for Determining the Nature of Dark Matter
Authors: Dan Hooper and Edward A. Baltz
Categories: hep-ph astro-ph
Comments: 25 pages, 5 figures, Review intended for the Annual Review of Nuclear
and Particle Science
Report-no: FERMILAB-PUB-08-026-A
In this review, we discuss the role of the various experimental programs
taking part in the broader effort to identify the particle nature of dark
matter. In particular, we focus on electroweak scale dark matter particles and
discuss a wide range of search strategies being carried out and developed to
detect them. These efforts include direct detection experiments, which attempt
to observe the elastic scattering of dark matter particles with nuclei,
indirect detection experiments, which search for photons, antimatter and
neutrinos produced as a result of dark matter annihilations, and collider
searches for new TeV-scale physics. Each of these techniques could potentially
provide a different and complementary set of information related to the mass,
interactions and distribution of dark matter. Ultimately, it is hoped that
these many different tools will be used together to conclusively identify the
particle or particles that constitute the dark matter of our universe.
\\ ( http://arxiv.org/abs/0802.0702 , 134kb)
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arXiv:0803.1438
Date: Mon, 10 Mar 2008 15:20:05 GMT (565kb,D)
Title: Gomez's Hamburger (IRAS 18059-3211): A pre main-sequence A-type star
Authors: V. Bujarrabal, K. Young, D. Fong
Categories: astro-ph
Comments: 8 pages, 4 figures, + aa.cls + bbl file
License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
We aim to study the nature of Gomez's Hamburger (IRAS 18059-3211), a nebula
that has been proposed to be a post-AGB object. Such a classification is not
confirmed, instead we argue that it will be a key object in the study of disks
rotating around young stars.
We present high resolution SMA maps of CO J=2--1 in Gomez's Hamburger. The
data are analyzed by means of a code that simulates the emission of a nebula
showing a variety of physical conditions and kinematics.
Our observations clearly show that the CO emitting gas in Gomez's Hamburger
forms a spectacular disk in keplerian rotation. Model calculations undoubtly
confirm this result. The central (mainly stellar) mass is found to be high, ~ 4
Mo for a distance of 500 pc. The mass and (relatively low) luminosity of the
source are, independently of the assumed distance, very different from those
possible in evolved stars. Gomez's Hamburger is probably a transitional object
between the pre-MS and MS phases, still showing interstellar material around
the central star or stellar system.
\\ ( http://arxiv.org/abs/0803.1438 , 565kb)
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The Cosmic Neutrino Background and the Age of the Universe
Authors: Francesco de Bernardis (Rome), Alessandro Melchiorri (Rome), Licia
Verde (ICE & Princeton), Raul Jimenez (ICE & Princeton)
(Submitted on 27 Jul 2007 (v1), last revised 8 Mar 2008 (this version, v2))
Abstract: We discuss the cosmological degeneracy between the age of the
Universe, the Hubble parameter and the effective number of relativistic
particles N_eff. We show that independent determinations of the Hubble
parameter H(z) as those recently provided by Simon,Verde, Jimenez (2006),
combined with other cosmological data sets can provide the most stringent
constraint on N_eff, yielding N_eff=3.7 (-1.2) (+1.1) at 95% confidence
level. A neutrino background is detected with high significance: N_eff >1.8
at better than 99% confidence level. Constraints on the age of the universe
in the framework of an extra background of relativistic particles are
improved by a factor 3.
http://arxiv.org/abs/0707.4170
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arXiv:0803.4164
Date: Fri, 28 Mar 2008 16:41:03 GMT (63kb)
Title: The energy output of the Universe from 0.1 micron to 1000 micron
Authors: Simon P. Driver (St Andrews), Cristina C. Popescu (UCLan), Richard J.
Tuffs (MPIK), Alister W. Graham (Swin.), Jochen Liske (ESO), Ivan Baldry
(LJMU)
Categories: astro-ph
Comments: Accepted by ApJ Letters
License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
The dominant source of electromagnetic energy in the Universe today (over
ultraviolet, optical and near-infrared wavelengths) is starlight. However,
quantifying the amount of starlight produced has proven difficult due to
interstellar dust grains which attenuate some unknown fraction of the light.
Combining a recently calibrated galactic dust model with observations of 10,000
nearby galaxies we find that (integrated over all galaxy types and
orientations) only (11 +/- 2)% of the 0.1 micron photons escape their host
galaxies; this value rises linearly (with log(lambda)) to (87 +/- 3)% at 2.1
micron. We deduce that the energy output from stars in the nearby Universe is
(1.6+/-0.2) x 10^{35} W Mpc^{-3} of which (0.9+/-0.1) x 10^{35} W Mpc^{-3}
escapes directly into the inter-galactic medium. Some further ramifications of
dust attenuation are discussed, and equations that correct individual galaxy
flux measurements for its effect are provided.
\\ ( http://arxiv.org/abs/0803.4164 , 63kb)
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Improved Constraints on the Acceleration History of the Universe and the
Properties of the Dark Energy
Ruth A. Daly, S. G. Djorgovski, Kenneth A. Freeman, Matthew P. Mory, C. P. O
http://www.journals.uchicago.edu/doi/full/10.1086/528837
------------------------------------------------------------------------------
Adaptive optics, near-infrared observations of magnetars:
V. Testa, N. Rea, R.?P. Mignani, G.?L. Israel, R. Perna, S. Chaty, L. Stella, S.
Covino, R. Turolla, S. Zane, G. Lo Curto, S. Campana, G. Marconi and
S. Mereghetti
A&A 482 (2008) 607-615
http://www.aanda.org/10.1051/0004-6361:20078692
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Persistent circumpolar vortices on the extrasolar giant planet HD?37605 b:
J. Langton and G. Laughlin
A&A 483 (2008) L25-L28
http://www.aanda.org/10.1051/0004-6361:200809417
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arXiv:0806.2815
Date: Tue, 17 Jun 2008 15:07:28 GMT (114kb)
Title: The very massive binary NGC3603-A1
Authors: O. Schnurr, A. F. J. Moffat, N. St-Louis, J. Casoli, and A.-N. Chen\'e
Categories: astro-ph
Comments: 5 pages, 4 figures; accepted for MNRAS Letters
Using VLT/SINFONI, we have obtained repeated AO-assisted, NIR spectroscopy of
the three central WN6ha stars in the core of the very young (~1 Myr), massive
and dense Galactic cluster NGC3603. One of these stars, NGC3603-A1, is a known
3.77-day, double-eclipsing binary, while another one, NGC3603-C, is one of the
brightest X-ray sources among all known Galactic WR stars, which usually is a
strong indication for binarity. Our study reveals that star C is indeed an
8.9-day binary, although only the WN6ha component is visible in our spectra;
therefore we temporarily classify star C as an SB1 system. A1, on the other
hand, is found to consist of two emission-line stars of similar, but not
necessarily of identical spectral type, which can be followed over most the
orbit. Using radial velocities for both components and the previously known
inclination angle of the system, we are able to derive absolute masses for both
stars in A1. We find M_1 = (116 \pm 31) Mo for the primary and M_2 = (89 \pm
16) Mo for the secondary component of A1. While uncertainties are large, A1 is
intrinsically half a magnitude brighter than WR20a, the current record holder
with 83 and 82 Mo, respectively; therefore, it is likely that the primary in A1
is indeed the most massive star weighed so far.
\\ ( http://arxiv.org/abs/0806.2815 , 114kb)
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arXiv:0806.3220
Date: Thu, 19 Jun 2008 15:33:12 GMT (459kb)
Title: Ultra-High Energy Cosmic Rays Detected by the Pierre Auger
Observatory: First Direct Evidence, and its Implications, that a
Subset Originate in Nearby Radiogalaxies
Authors: Neil M. Nagar (U. de Concepcion), Javier Matulich (U. de
Concepcion)
CategOries: astro-ph
Comments: 10 pages total. To appear in A&A
(abridged) The Pierre Auger Collaboration has reported 27 Ultra-High
Energy Cosmic Ray Events (UHECRs) with energies above 56 EeV and well
determined arrival directions as of 2007 August 31. They find that the
arrival directions are not isotropic, but instead appear correlated
with the positions of nearby AGNs. Our aim was to determine the
sources of these UHECRs by comparing their arrival directions with
more comprehensive source catalogs. Four (eight) of the 27 UHECRs
with energy >56EeV detected by the Pierre Auger Observatory have
arrival directions within 1.5deg (3.5deg) of the extended (>180kpc)
radio structures of nearby radiogalaxies or the single nearby BLLac
with extended radio structure. Conversely the radio structures of
three (six) of all ten nearest extended radiogalaxies are within
1.5deg (3.5deg) of a UHECR; three of the remaining four radiogalaxies
are in directions with lower exposure times. This correlation between
nearby extended radiogalaxies and a subset of UHECRs is significant at
the 99.9% level. This is the first direct observational proof that
radio galaxies are a significant source of UHECRs. For the remaining
~20 UHECRs, an isotropic distribution cannot be ruled out at high
significance. The correlation found by the Auger Collaboration between
the 27 UHECRs and AGNs in the Veron-Cetty & Veron catalog at D < 71Mpc
has a much lower significance when one considers only the ~20 UHECRs
not `matched' to nearby extended radiogalaxies. No correlation is seen
between UHECRs and supernovae, supernova remnants, nearby galaxies, or
nearby groups and clusters of galaxies. The primary difference between
the UHECR detections at the Pierre Auger Observatory and previous
experiments may thus be that the Southern Hemisphere is more
privileged with respect to nearby extended radiogalaxies.
\\ ( http://arxiv.org/abs/0806.3220 , 459kb)
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arXiv:0805.0140
Title: Stellar Exotica in 47 Tucanae
Authors: Christian Knigge (1), Andrea Dieball (1), Jesus Maiz
Apellaniz (2),
Knox S. Long (3), David R. Zurek (4), Michael M. Shara (4) ((1)
University of
Southampton, (2) IAA-CSIC, (3) STSCI, (4) AMNH)
CategOries: astro-ph
Comments: 28 pages, 22 figures, 1 table, accepted for publication in
ApJ; abstract below is abridged; new version corrects some typos and
updates some references; a copy with some higher resolution figures is
available from
http://www.astro.soton.ac.uk/~christian (under "Research")
\\ ( http://arxiv.org/abs/0805.0140 , 2328kb)
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arXiv:0902.2084
Date: Thu, 12 Feb 2009 11:22:56 GMT (228kb)
Title: The Strange Prospects for Astrophysics
Authors: Irina Sagert, Matthias Hempel, Giuseppe Pagliara, Jurgen
Schaffner-Bielich, Tobias Fischer, Anthony Mezzacappa,
Friedrich-Karl
Thielemann, Matthias Liebendorfer
Categories: astro-ph.HE
Comments: 10 pages, 8 figures, invited talk given at the international
conference on strangeness in quark matter (SQM2008), Beijing,
October 6-10, Beijing, China
The implications of the formation of strange quark matter in neutron
stars and in core-collapse supernovae is discussed with special
emphasis on the possibility of having a strong first order QCD phase
transition at high baryon densities. If strange quark matter is formed
in core-collapse supernovae shortly after the bounce, it causes the
launch of a second outgoing shock which is energetic enough to lead to
a explosion. A signal for the formation of strange quark matter can be
read off from the neutrino spectrum, as a second peak in antineutrinos
is released when the second shock runs over the neutrinosphere.
\\ ( http://arxiv.org/abs/0902.2084 , 228kb)
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959-968
Kinematics of the young stellar objects associated with the cometary
globules in the Gum Nebula
Rumpa Choudhury, H. C. Bhatt
Published Online: 31 Jan 2009
DOI 10.1111/j.1365-2966.2008.14189.x
http://www3.interscience.wiley.com/journal/121674411/abstract
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Massive star formation within the Leo `primordial' ring pp990-993
The Leo ring is a massive, 200-kpc-wide structure orbiting the
galaxies
M105 and NGC3384 with a 4-Gyr period. This paper reports ultraviolet
light originating from gaseous substructures, which is attributed to
recent massive star formation. If structures like the Leo ring were
common in the early Universe, they may have produced a large, yet
undetected population of faint, metal-poor, halo-lacking dwarf
galaxies.
David A. Thilker et al.
doi:10.1038/nature07780
Abstract:
http://links.ealert.nature.com/ctt?kn=224&m=31506956&r=MTc2MjIxMjgzNQS2&b=2&j=NDU5MTcyMDQS1&mt=1&r
t=0
Article:
http://links.ealert.nature.com/ctt?kn=79&m=31506956&r=MTc2MjIxMjgzNQS2&b=2&j=NDU5MTcyMDQS1&mt=1&rt
=0
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Volume 137, Number 4, 2009 April (3731-4082)
http://www.iop.org/EJ/toc/-alert=36011/1538-3881/137/4
Outflows and Young Stars in Orion's Large Cometary Clouds L1622 and
L1634
John Bally, Josh Walawender, Bo Reipurth, and S. Thomas Megeath
2009 The Astronomical Journal 137 3843-3858
Abstract:
http://www.iop.org/EJ/abstract/-alert=36011/1538-3881/137/4/3843
Full text PDF:
http://www.iop.org/EJ/article/-alert=36011/1538-3881/137/4/3843/aj_137_4_3843.pdf
Full text HTML:
http://www.iop.org/EJ/article/-alert=36011/1538-3881/137/4/3843/aj_137_4_3843.html
New observations of protostellar outflows associated with young stars
in two of Orion's outlying cometary clouds, L1622 and L1634, are
presented. The Ha surface brightness of the bright rims are used to
argue that both clouds are located at a distance of about 400 pc in
the interior of the Orion superbubble where they are illuminated by
Orion's massive stars. Spitzer IRAC and MIPS images reveal 28
candidate young stellar objects (YSOs). Combined with the 14
spectroscopically confirmed T Tauri stars, there are at least 34 YSOs
in L1622. Narrow-band images have led to the identification of about a
dozen shock complexes in L1622. At least six belong to a highly
collimated externally irradiated, bipolar jet, HH 963, that is powered
by a low-luminosity Class II YSO located outside the projected edge of
the L1622 dark cloud. However, the sources of most shocks remain
unclear. The Spitzer/IRAC images reveal a compact, highly obscured,
S-symmetric outflow brightest in the 4.5 mm images. A faint [S II]
counter part, HH 962, is associated with the western end of this flow
which appears to be powered by an obscured source in the L1622 cloud
interior. The currently identified sample of YSOs implies a star
formation efficiency of about 4% for L1622. The L1634 cloud contains
nine YSOs and three outflows, including the well known HH 240/241
system. A new flow, HH 979, is powered by the embedded YSO IRS7 in
L1634 and crosses the eastern lobe of the HH 240 outflow. Spitzer/IRAC
images show 4.5 mm emission indicating molecular shocks from the
Herbig-Haro objects closest to IRS 7. A YSO embedded in a condensation
located 5' north of HH 240/241 is identified in the Spitzer
images. This source drives an irradiated outflow, HH 980, whose lobes
emerge into the ionized environment of the Orion-Eridanus superbubble
interior. The star formation efficiency of L1634 is estimated to be
about 3%.
------------------------------------------------------------------------------
arXiv:0903.3070
Date: Wed, 18 Mar 2009 17:42:47 GMT (96kb)
Title: Dark Stars: a new look at the First Stars in the Universe
Authors: Douglas Spolyar, Peter Bodenheimer, Katherine Freese, and
Palo Gondolo
Categories: astro-ph.CO
Comments: 14 pages, 4 figures, 1 Table, Submitted to APJ
We have proposed that the first phase of stellar evolution in the
history of the Universe may be Dark Stars (DS), powered by dark matter
heating rather than by nuclear fusion, and in this paper we examine
the history of these DS. The power source is annihilation of Weakly
Interacting Massive Particles (WIMPs) which are their own
antiparticles. These WIMPs are the best motivated dark matter (DM)
candidates and may be discovered by ongoing direct or indirect
detection searches (e.g. FERMI /GLAST) or at the Large Hadron Collider
at CERN. A new stellar phase results, powered by DM annihilation as
long as there is DM fuel, from millions to billions of years. We build
up the dark stars from the time DM heating becomes the dominant power
source, accreting more and more matter onto them. We have included
many new effects in the current study, including a variety of particle
masses and accretion rates, nuclear burning, feedback mechanisms, and
possible repopulation of DM density due to capture. Remarkably, we
find that in all these cases, we obtain the same result: the first
stars are very large, 500-1000 times as massive as the Sun; as well as
puffy (radii 1-10 A.U.), bright ($10^6-10^7 L_\odot$), and cool
($T_{surf} < $10,000 K) during the accretion. These results differ
markedly from the standard picture in the absence of DM heating. Hence
DS should be observationally distinct from standard Pop III stars. In
addition, DS avoid the (unobserved) element enrichment produced by the
standard first stars. Once the dark matter fuel is exhausted, the DS
becomes a heavy main sequence star; these stars eventually collapse to
form massive black holes that may provide seeds for the supermassive
black holes and intermediate black holes, and explain ARCADE data.
\\ ( http://arxiv.org/abs/0903.3070 , 96kb)
------------------------------------------------------------------------------
arXiv:0905.1696
Date: Mon, 11 May 2009 20:13:03 GMT (518kb)
Title: How common is the Milky Way - satellite system alignment?
Authors: Noam I Libeskind, Carlos S Frenk, Shaun Cole, Adrian Jenkins,
John C Helly
Categories: astro-ph.CO
Comments: 12 Pages, 10 Figures, Submitted to MNRAS
The highly flattened distribution of satellite galaxies in the Milky
Way presents a number of puzzles. Firstly, its polar alignment stands
out from the planar alignments commonly found in other
galaxies. Secondly, recent proper motion measurements reveal that the
orbital angular momentum of at least 3, and possibly as many as 8, of
the Milky Ways satellites point (within 30 degrees) along the axis of
their flattened configuration, suggesting some form of coherent
motion. In this paper we use a high resolution cosmological simulation
to investigate whether this pattern conflicts with the expectations of
the cold dark matter model of structure formation. We find that this
seemingly unlikely set up occurs often: approximately 35% of the time
we find systems in which the angular momentum of 3 individual
satellites point along, or close to, the short axis of the satellite
distribution. In addition, in 30% of the systems we find that the net
angular momentum of the 6 best aligned satellites lies within 35
degrees of the short axis of the satellite distribution, as observed
for the Milky Way.
\\ ( http://arxiv.org/abs/0905.1696 , 518kb)
------------------------------------------------------------------------------
The Physical Properties of the Red Supergiant WOH G64: The Largest
Star Known?
Emily M. Levesque, Philip Massey, Bertrand Plez, and Knut A. G. Olsen
2009 The Astronomical Journal 137 4744-4752
Abstract:
http://www.iop.org/EJ/abstract/-alert=36013/1538-3881/137/6/4744
Full text PDF:
http://www.iop.org/EJ/article/-alert=36013/1538-3881/137/6/4744/aj_137_6_4744.pdf
Full text HTML:
http://www.iop.org/EJ/article/-alert=36013/1538-3881/137/6/4744/aj_137_6_4744.html
WOH G64 is an unusual red supergiant (RSG) in the Large Magellanic
Cloud (LMC), with a number of properties that set it apart from the
rest of the LMC RSG population, including a thick circumstellar dust
torus, an unusually late spectral type, maser activity, and nebular
emission lines. Its reported physical properties are also extreme,
including the largest radius for any star known and an effective
temperature that is much cooler than other RSGs in the LMC, both of
which are at variance with stellar evolutionary theory. We fit
moderate-resolution optical spectrophotometry of WOH G64 with the
MARCS stellar atmosphere models, determining an effective temperature
of 3400 +- 25 K. We obtain a similar result from the star's broadband
V - K colors. With this effective temperature, and taking into account
the flux contribution from the asymmetric circumstellar dust envelope,
we calculate log(L/L ) = 5.45 +- 0.05 for WOH G64, quite similar to
the luminosity reported by Ohnaka and collaborators based on their
radiative transfer modeling of the star's dust torus. We determine a
radius of R/R = 1540, bringing the size of WOH G64 and its position on
the Hertzsprung-Russell diagram into agreement with the largest known
Galactic RSGs, although it is still extreme for the LMC. In addition,
we use the Ca II triplet absorption feature to determine a radial
velocity of 294 +- 2 km s-1 for the star; this is the same radial
velocity as the rotating gas in the LMC's disk, which confirms its
membership in the LMC and precludes it from being an unusual Galactic
halo giant. Finally, we describe the star's unusual nebula emission
spectrum; the gas is nitrogen-rich and shock-heated, and displays a
radial velocity that is significantly more positive than the star
itself by 50 km s-1.
------------------------------------------------------------------------------
arXiv:0906.5117
Date: Sun, 28 Jun 2009 06:53:31 GMT (889kb)
Title: Dark impact and galactic star formation: Origin of the Gould belt
Authors: Kenji Bekki
Categories: astro-ph.GA astro-ph.CO
Comments: 5 pages, 4 figures, accepted by MNRAS Letters
\\
The Milky Way has a giant stellar structure in the solar neighborhood, which
has a size of $\sim 1$ kpc, a mass of $\sim 10^6 {\rm M}_{\odot}$, and a
ring-like distribution of young stars. Fundamental physical properties of this
local enigmatic structure, known as the Gould belt (GB), have not been
reproduced by previously proposed models. We first show that the local
enigmatic structure can be formed about 30 Myr ago as a result of a high-speed,
oblique collision between a gas cloud with a mass of $\sim 10^6 {\rm
M}_{\odot}$ and a dark matter clump with a mass of $\sim 10^7 {\rm M}_{\odot}$
based on numerical simulations of the collision. We find that strong dynamical
impact of the clump transforms the flattened cloud into a ring-like stellar
structure after induced star formation within the cloud. Our simulations
furthermore demonstrate that the stellar structure is moderately elongated and
significantly inclined with respect to the disk of the Milky Way owing to the
strong tidal torque by the colliding clump. We thus suggest that the GB is one
of stellar substructures formed from collisions between gas clouds and dark
matter clumps predicted in the hierarchical clustering scenario of galaxy
formation. We also suggest that collisions of dark matter clumps with their
host galaxies can significantly change star formation histories for some of
their gas clouds thus influence galactic global star formation histories to
some extent.
\\ ( http://arxiv.org/abs/0906.5117 , 889kb)
------------------------------------------------------------------------------
arXiv:0906.5304
Date: Mon, 29 Jun 2009 15:49:46 GMT (1569kb)
Title: Galaxy Zoo : 'Hanny's Voorwerp', a quasar light echo?
Authors: Chris Lintott, Kevin Schawinski, William Keel, Hanny van
Arkel, Nicola Bennert, Edward Edmondson, Daniel Thomas, Daniel Smith,
Peter Herbert, Matt Jarvis, Shanil Virani, Dan Andreescu, Steven
Bamford, Kate Land, Phil Murray, Robert Nichol, Jordan Raddick, Anze
Slosar, Alex Szalay, Jan Vandenberg
Categories: astro-ph.CO
Comments: 13 pages, 10 figures, Accepted by MNRAS
We report the discovery of an unusual object near the spiral galaxy IC
2497, discovered by visual inspection of the Sloan Digital Sky Survey
(SDSS) as part of the Galaxy Zoo project. The object, known as Hanny's
Voorwerp, is bright in the SDSS g band due to unusually strong OIII
4959-5007 emission lines. We present the results of the first targeted
observations of the object in the optical, UV and X-ray, which show
that the object contains highly ionized gas. Although the line ratios
are similar to extended emission-line regions near luminous AGN, the
source of this ionization is not apparent. The emission-line
properties, and lack of x-ray emission from IC 2497, suggest either a
highly obscured AGN with a novel geometry arranged to allow
photoionization of the object but not the galaxy's own circumnuclear
gas, or, as we argue, the first detection of a quasar light echo. In
this case, either the luminosity of the central source has decreased
dramatically or else the obscuration in the system has increased
within 10^5 years. This object may thus represent the first direct
probe of quasar history on these timescales.
\\ ( http://arxiv.org/abs/0906.5304 , 1569kb)
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arXiv:0906.5350
Date: Tue, 30 Jun 2009 19:12:54 GMT (1048kb)
Title: The Palomar Transient Factory: System Overview, Performance and
First Results
Authors: N.M. Law, S.R. Kulkarni, R.G. Dekany, E.O. Ofek, R.M. Quimby,
P.E. Nugent, J. Surace, C.C. Grillmair, J.S. Bloom, M.M. Kasliwal,
L. Bildsten, T. Brown, S.B. Cenko, D. Ciardi, E. Croner,
S.G. Djorgovski, J.C. van Eyken, A.V. Filippenko, D.B. Fox,
A. Gal-Yam, D. Hale, N. Hamam, G. Helou, J.R. Henning, D.A. Howell,
J. Jacobsen, R. Laher, S. Mattingly, D. McKenna, A. Pickles,
D. Poznanski, G. Rahmer, A. Rau, W. Rosing, M. Shara, R. Smith, D.
Starr, M. Sullivan, V. Velur, R.S. Walters, J. Zolkower
Categories: astro-ph.IM astro-ph.CO
Comments: 12 pages, 11 figures, 3 tables, submitted to PASP
The Palomar Transient Factory (PTF) is a fully-automated, wide-field
survey aimed at a systematic exploration of the optical transient
sky. The transient survey is performed using a new 8.1 square degree
camera installed on the 48-inch Samuel Oschin telescope at Palomar
Observatory; colors and light curves for detected transients are
obtained with the automated Palomar 60-inch telescope. PTF uses eighty
percent of the 1.2-m and fifty percent of the 1.5-m telescope
time. With an exposure of 60-s the survey reaches a depth of
approximately 21.3 in g' and 20.6 in R (5 sigma, median seeing). Four
major experiments are planned for the five-year project: 1) a 5-day
cadence supernova search; 2) a rapid transient search with cadences
between 90 seconds and 1 day; 3) a search for eclipsing binaries and
transiting planets in Orion; and 4) a 3-pi sr deep H-alpha survey. PTF
provides automatic, realtime transient classification and follow up,
as well as a database including every source detected in each
frame. This paper summarizes the PTF project, including several months
of on-sky performance tests of the new survey camera, the observing
plans and the data reduction strategy. We conclude by detailing the
first 51 PTF optical transient detections, found in commissioning
data.
\\ ( http://arxiv.org/abs/0906.5350 , 1048kb)
------------------------------------------------------------------------------
Automated Variable Star Classification Using the Northern Sky
Variability Survey
D. I. Hoffman, T. E. Harrison, and B. J. McNamara
2009 The Astronomical Journal 138 466-477
Abstract:
http://www.iop.org/EJ/abstract/-alert=36013/1538-3881/138/2/466
Full text PDF:
http://www.iop.org/EJ/article/-alert=36013/1538-3881/138/2/466/aj_138_2_466.pdf
Full text HTML:
http://www.iop.org/EJ/article/-alert=36013/1538-3881/138/2/466/aj_138_2_466.html
We have identified 4659 variable objects in the Northern Sky
Variability Survey. We have classified each of these objects into
one of the five variable star classes: (1) Algol/b Lyr systems
including semidetached, and detached eclipsing binaries, (2) W
Ursae
Majoris overcontact and ellipsoidal variables, (3) long-period
variables such as Cepheid and Mira-type objects, (4) RR Lyr
pulsating variables, and (5) short-period variables including d
Scuti stars. All the candidates have outside of eclipse magnitudes
of [?]10-13. The primary classification tool is the use of Fourier
coefficients combined with period information and light-curve
properties to make the initial classification. Brief manual
inspection was done on all light curves to remove nonperiodic
variables that happened to slip through the process and to quantify
any errors in the classification pipeline. We list the coordinates,
period, Two Micron All Sky Survey colors, total amplitude
variation,
and any previous classification of the object. 548 objects
previously identified as Algols in our previous paper are not
included here.
------------------------------------------------------------------------------
 2049-2056
VLT/SINFONI time-resolved spectroscopy of the central, luminous,
H-rich WN stars of
R136★
O. Schnurr, A.-N. Chen?, J. Casoli, A. F. J. Moffat, N. St-Louis
Abstract
Published Online: 24 Jul 2009
DOI 10.1111/j.1365-2966.2009.15060.x
http://www3.interscience.wiley.com/journal/122522062/abstract
------------------------------------------------------------------------------
Where Is the Best Site on Earth? Domes A, B, C, and F, and Ridges A and B
Will Saunders, Jon S. Lawrence, John W. V. Storey, Michael C. B. Ashley, Seiji Kato,
Patrick Minnis, David M. Winker, Guiping Liu, and Craig Kulesa
Publications of the Astronomical Society of the Pacific September 2009, Vol. 121, No. 883:
976-992.
Abstract [www.journals.uchicago.edu] | Full Text [www.journals.uchicago.edu] | PDF Version
(2551 KB) [www.journals.uchicago.edu]
http://www.journals.uchicago.edu/doi/full/10.1086/605780
------------------------------------------------------------------------------
arXiv:0911.3391
Date: Tue, 17 Nov 2009 21:14:40 GMT (154kb)
Title: The distance to the Andromeda Galaxy from eclipsing binaries
Authors: F. Vilardell, I. Ribas, C. Jordi, E. L. Fitzpatrick and E. F. Guinan
Categories: astro-ph.CO astro-ph.SR
Comments: 7 pages, 3 figures, accepted for publication in A&A (Nov 6, 2009)
The cosmic distance scale largely depends on distance determinations to Local
Group galaxies. In this sense, the Andromeda Galaxy (M31) is a key rung to
better constrain the cosmic distance ladder. A project was started in 1999 to
firmly establish a direct and accurate distance to M31 using eclipsing binaries
(EBs). After the determination of the first direct distance to M31 from EBs,
the second direct distance to an EB system is presented:
M31V_J00443610+4129194. Light and radial velocity curves were obtained and
fitted to derive the masses and radii of the components. The acquired spectra
were combined and disentangled to determine the temperature of the components.
The analysis of the studied EB resulted in a distance determination to M31 of
(m-M)o = 24.30 +/- 0.11 mag. This result, when combined with the previous
distance determination to M31, results in a distance modulus of (m-M)o = 24.36
+/- 0.08 mag (744 +/- 33 kpc), fully compatible with other distance
determinations to M31. With an error of only 4%, the obtained value firmly
establishes the distance to this important galaxy and represents the
fulfillment of the main goal of our project.
\\ ( http://arxiv.org/abs/0911.3391 , 154kb)
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arXiv:0911.3507
Date: Wed, 18 Nov 2009 11:06:26 GMT (130kb,D)
Title: Correlation between technetium and lithium in a sample of oxygen-rich
AGB variables
Authors: Stefan Uttenthaler (Instituut voor Sterrenkunde, K. U. Leuven,
Belgium) and Thomas Lebzelter (Department of Astronomy, University of Vienna,
Austria)
Categories: astro-ph.SR
Comments: 12 pages, 7 figures, accepted for publication in A&A
The aims of this paper are: 1) to revisit the Tc content of a sample of
oxygen-rich asymptotic giant branch (AGB) variables and 2) to increase the
number of such stars for which the Li abundance has been measured to provide
constraints on theoretical models of extra-mixing processes. To this end, we
analysed high-resolution spectra of 18 sample stars for the presence of
absorption lines of Tc and Li. The abundance of the latter was determined by
comparing the observed spectra to hydrostatic MARCS model spectra. Bolometric
magnitudes were established from near-IR photometry and pulsation periods. We
reclassify the star V441 Cyg as Tc-rich, and the unusual Mira star R Hya, as
well as W Eri, as Tc-poor. The abundance of Li, or an upper limit to it, was
determined for all of the sample stars. In all stars with Tc we also detected
Li. Most of them have a Li content slightly below the solar photospheric value,
except for V441 Cyg, which has ~1000 times the solar abundance. We also found
that, similar to Tc, a lower luminosity limit seems to exist for the presence
of Li. We conclude that the higher Li abundance found in the cooler and higher
luminosity objects could stem from a Li production mechanism operating on the
AGB. The stellar mass might have a crucial influence on this (extra-mixing)
production mechanism. It was speculated that the declining pulsation period of
R Hya is caused by a recent thermal pulse (TP). While not detecting Tc does not
rule out a TP, it indicates that the TPs are not strong enough to drive
dredge-up in R Hya. V441 Cyg, on the other hand, could either be a low-mass,
intrinsic S-star that produced its large amount of Li by extra-mixing
processes, or an intermediate-mass star (M>=M_sun) undergoing Li production due
to hot bottom burning.
\\ ( http://arxiv.org/abs/0911.3507 , 130kb)
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arXiv:1004.1475
Date: Fri, 9 Apr 2010 07:15:26 GMT (315kb)
Title: Offset between dark matter and ordinary matter: evidence from a sample
of 38 lensing clusters of galaxies
Authors: HuanYuan Shan, Bo Qin, Bernard Fort, Charling Tao, Xiang-Ping Wu,
HongSheng Zhao
Categories: astro-ph.CO
Comments: 6 pages, 1 figure, 1 table, accepted for publication in MNRAS
\\
We compile a sample of 38 galaxy clusters which have both X-ray and strong
lensing observations, and study for each cluster the projected offset between
the dominant component of baryonic matter center (measured by X-rays) and the
gravitational center (measured by strong lensing). Among the total sample, 45%
clusters have offsets >10". The >10" separations are significant, considering
the arcsecond precision in the measurement of the lensing/X-ray centers. This
suggests that it might be a common phenomenon in unrelaxed galaxy clusters that
gravitational field is separated spatially from the dominant component of
baryonic matter. It also has consequences for lensing models of unrelaxed
clusters since the gas mass distribution may differ from the dark matter
distribution and give perturbations to the modeling. Such offsets can be used
as a statistical tool for comparison with the results of Lambda-CDM simulations
and to test the modified dynamics.
\\ ( http://arxiv.org/abs/1004.1475 , 315kb)
------------------------------------------------------------------------------
 863-880Â
The end of the rainbow: what can we say about the extragalactic sub-megahertz
radio sky?
Brian C. Lacki
Abstract
Published Online: 15 Jun 2010
DOI 10.1111/j.1365-2966.2010.16781.x
------------------------------------------------------------------------------
Nemesis reconsidered (pages L99–L102) [onlinelibrary.wiley.com]
Adrian L. Melott and Richard K. Bambach
Article first published online: 1 JUL 2010 | DOI: 10.1111/j.1745-3933.2010.00913.x
------------------------------------------------------------------------------
arXiv:1009.0925
Date: Sun, 5 Sep 2010 15:49:47 GMT (10kb)
Title: The Futile Search for Galactic Disk Dark Matter
Authors: Jos\'{e} Luis G. Pesta\~{n}a and Donald H. Eckhardt
Categories: astro-ph.GA
Comments: Accepted for publication in ApJ Letters
\\
Several approaches have been used to search for dark matter in our galactic
disk, but with mixed results: {\em maybe yes and maybe no}. The prevailing
approach, integrating the Poisson-Boltzmann equation for tracer stars, has led
to more definitive results: {\em yes and no}. The touchstone {\em yes} analysis
of Bahcall et al. (1992) has subsequently been confirmed or refuted by various
other investigators. This has been our motivation for approaching the search
from a different direction: applying the Virial Theorem to extant data. We
conclude that the vertical density profile of the disk is not in a state of
equilbrium and, therefore, that the Poisson-Boltzmann approach is inappropriate
and it thereby leads to indefensible conclusions.
\\ ( http://arxiv.org/abs/1009.0925 , 10kb)
------------------------------------------------------------------------------
A PROBLEM WITH THE CLUSTERING OF RECENT MEASURES OF THE DISTANCE TO
THE LARGE MAGELLANIC CLOUD
Bradley E. Schaefer
http://iopscience.iop.org/1538-3881/135/1/112/fulltext
------------------------------------------------------------------------------
arXiv:1102.2985
Date: Tue, 15 Feb 2011 07:46:27 GMT (66kb)
Title: Detection of C60 in the proto-planetary nebula IRAS 01005+7910
Authors: Yong Zhang, Sun Kwok
Categories: astro-ph.SR
Comments: 14 pages, 4 figures, accepted for publication in ApJ
\\
We report the first detection of buckminsterfullerene (C60) in a
proto-planetary nebula (PPN). The vibrational transitions of C60 at 7.0, 17.4,
and 18.9um are detected in the Spitzer/IRS spectrum of IRAS 01005+7910. This
detection suggests that fullerenes are formed shortly after the asymptotic
giant branch but before the planetary nebulae stage. A comparison with the
observations of C60 in other sources is made and the implication on
circumstellar chemistry is discussed.
\\ ( http://arxiv.org/abs/1102.2985 , 66kb)
------------------------------------------------------------------------------
Gravity modes as a way to distinguish between hydrogen- and
helium-burning red giant stars
Timothy R. Bedding et al
http://arxiv.org/abs/1103.5805
Abstract: Red giants are evolved stars that have exhausted the supply
of hydrogen in their cores and instead burn hydrogen in a surrounding
shell. Once a red giant is sufficiently evolved, the helium in the
core also undergoes fusion. Outstanding issues in our understanding of
red giants include uncertainties in the amount of mass lost at the
surface before helium ignition and the amount of internal mixing from
rotation and other processes. Progress is hampered by our inability to
distinguish between red giants burning helium in the core and those
still only burning hydrogen in a shell. Asteroseismology offers a way
forward, being a powerful tool for probing the internal structures of
stars using their natural oscillation frequencies. Here we report
observations of gravity-mode period spacings in red giants that permit
a distinction between evolutionary stages to be made. We use
high-precision photometry obtained with the Kepler spacecraft over
more than a year to measure oscillations in several hundred red
giants. We find many stars whose dipole modes show sequences with
approximately regular period spacings. These stars fall into two clear
groups, allowing us to distinguish unambiguously between
hydrogen-shell-burning stars (period spacing mostly about 50 seconds)
and those that are also burning helium (period spacing about 100 to
300 seconds).
------------------------------------------------------------------------------
Hydrogen-poor superluminous stellar explosions
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10095.html?WT.ec_id=NATURE-20110609
R. M. Quimby et al
Nature (2011)
doi:10.1038/nature10095
Received: 17 February 2011
Accepted: 01 April 2011
Published online: 08 June 2011
Supernovae are stellar explosions driven by gravitational or
thermonuclear energy that is observed as electromagnetic radiation
emitted over weeks or more1. In all known supernovae, this radiation
comes from internal energy deposited in the outflowing ejecta by one
or more of the following processes: radioactive decay of freshly
synthesized elements2 (typically 56Ni), the explosion shock in the
envelope of a supergiant star3, and interaction between the debris and
slowly moving, hydrogen-rich circumstellar material4. Here we report
observations of a class of luminous supernovae whose properties cannot
be explained by any of these processes. The class includes four new
supernovae that we have discovered and two previously unexplained
events5, 6 (SN 2005ap and SCP 06F6) that we can now identify as
members of the same class. These supernovae are all about ten times
brighter than most type Ia supernova, do not show any trace of
hydrogen, emit significant ultraviolet flux for extended periods of
time and have late-time decay rates that are inconsistent with
radioactivity. Our data require that the observed radiation be emitted
by hydrogen-free material distributed over a large radius (~1015
centimetres) and expanding at high speeds (>104 kilometres per
second). These long-lived, ultraviolet-luminous events can be observed
out to redshifts z > 4.
------------------------------------------------------------------------------
X-ray illumination of the ejecta of Supernova 1987A
Authors: J. Larsson et al
We present the late-time optical light curve of the ejecta of SN 1987A
measured from HST imaging observations spanning the past 17 years. We
find that the flux from the ejecta declined up to around year 2001,
powered by the radioactive decay of 44Ti. Then the flux started to
increase, more than doubling by the end of 2009. We show that the
increase is the result of energy deposited by X-rays produced in the
interaction with the circumstellar medium. We suggest that the change
of the dominant energy input to the ejecta, from internal to external,
marks the transition from supernova to supernova remnant. The details
of the observations and the modelling are described in the
accompanying supplementary information.
http://arxiv.org/abs/1106.2300
------------------------------------------------------------------------------
arXiv:1107.4029
Date: Wed, 20 Jul 2011 16:50:18 GMT (302kb)
Title: Galactic S Stars: Investigations of Color, Motion, and Spectral Features
Authors: Elizabeth Otto, Paul J Green, Richard O. Gray
Categories: astro-ph.SR astro-ph.GA
Comments: 11 pages. Accepted for publication in ApJS July 19, 2011. Spectra
available as http://hea-www.harvard.edu/~pgreen/SStarAtlas.tar
\\
Known bright S stars, recognized as such by their enhanced s-process
abundances and C/O ratio, are typically members of the asymptotic giant branch
(AGB) or the red giant branch (RGB). Few modern digital spectra for these
objects have been published, from which intermediate resolution spectral
indices and classifications could be derived. For published S stars we find
accurate positions using the Two-Micron All Sky Survey (2MASS), and use the
FAST spectrograph of the Tillinghast reflector on Mt. Hopkins to obtain the
spectra of 57 objects. We make available a digital S star spectral atlas
consisting of 14 spectra of S stars with diverse spectral features. We define
and derive basic spectral indices that can help distinguish S stars from
late-type (M) giants and carbon stars. We convolve all our spectra with the
SDSS bandpasses, and employ the resulting gri magnitudes together with 2MASS
JHK mags to investigate S star colors. S stars have colors similar to carbon
and M stars, and are therefore difficult to distinguish by color alone. Using
near and mid-infrared colors from IRAS and AKARI, we identify some of the stars
as intrinsic (AGB) or extrinsic (with abundances enhanced by past
mass-transfer). We also use V band and 2MASS magnitudes to calculate a
temperature index for stars in the sample. We analyze the proper motions and
parallaxes of our sample stars to determine upper and lower limit absolute
magnitudes and distances, and confirm that most are probably giants.
\\ ( http://arxiv.org/abs/1107.4029 , 302kb)
------------------------------------------------------------------------------
An extremely primitive star in the Galactic halo
* Elisabetta Caffau,1, 2
* Piercarlo Bonifacio,2
* Patrick François,2, 3
* Luca Sbordone,1, 2, 4
* Lorenzo Monaco,5
* Monique Spite,2
* François Spite,2
* Hans-G. Ludwig,1, 2
* Roger Cayrel,2
* Simone Zaggia,6
* François Hammer,2
* Sofia Randich,7
* Paolo Molaro8
* & Vanessa Hill
Nature
Volume:
477,
Pages:
67–69
Date published:
(01 September 2011)
DOI:
doi:10.1038/nature10377
Received
31 March 2011
Accepted
15 July 2011
Published online
31 August 2011
The early Universe had a chemical composition consisting of hydrogen,
helium and traces of lithium1; almost all other elements were
subsequently created in stars and supernovae. The mass fraction of
elements more massive than helium, Z, is known as ‘metallicity’. A
number of very metal-poor stars has been found2, 3, some of which have
a low iron abundance but are rich in carbon, nitrogen and oxygen4, 5,
6. For theoretical reasons7, 8 and because of an observed absence of
stars with Z < 1.5 × 10−5, it has been suggested that low-mass stars
cannot form from the primitive interstellar medium until it has been
enriched above a critical value of Z, estimated to lie in the range
1.5 × 10−8 to 1.5 × 10−6 (ref. 8), although competing theories
claiming the contrary do exist9. (We use ‘low-mass’ here to mean a
stellar mass of less than 0.8 solar masses, the stars that survive to
the present day.) Here we report the chemical composition of a star in
the Galactic halo with a very low Z (≤ 6.9 × 10−7, which is 4.5 × 10−5
times that of the Sun10) and a chemical pattern typical of classical
extremely metal-poor stars2, 3—that is, without enrichment of carbon,
nitrogen and oxygen. This shows that low-mass stars can be formed at
very low metallicity, that is, below the critical value of Z. Lithium
is not detected, suggesting a low-metallicity extension of the
previously observed trend in lithium depletion11. Such lithium
depletion implies that the stellar material must have experienced
temperatures above two million kelvin in its history, given that this
is necessary to destroy lithium.
http://www.nature.com/nature/journal/v477/n7362/full/nature10377.html?WT.ec_id=NATURE-20110901
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arXiv:1109.3979
Date: Mon, 19 Sep 2011 09:41:21 GMT (146kb,D)
Title: Magnetic field and convection in Betelgeuse
Authors: P. Petit, M. Auri\`ere, R. Konstantinova-Antova, A. Morgenthaler, G.
Perrin, T. Roudier, J.-F. Donati
Categories: astro-ph.SR
Comments: Submitted to Lecture Notes in Physics (CNRS astronomy school : "From
solar environment to stellar environment")
\\
We present the outcome of a highly-sensitive search for magnetic fields on
the cool supergiant Betelgeuse. A time-series of six circularly-polarized
spectra was obtained using the NARVAL spectropolarimeter at T\'elescope Bernard
Lyot (Pic du Midi Observatory), between 2010 March and April. Zeeman signatures
were repeatedly detected in cross-correlation profiles, corresponding to a
longitudinal component of about 1 G. The time-series unveils a smooth increase
of the longitudinal field from 0.5 to 1.5 G, correlated with radial velocity
fluctuations. We observe a strong asymmetry of Stokes V signatures, also
varying in correlation with the radial velocity. The Stokes V line profiles are
red-shifted by about 9 km/s with respect to the Stokes I profiles, suggesting
that the observed magnetic elements may be concentrated in the sinking
components of the convective flows.
\\ ( http://arxiv.org/abs/1109.3979 , 146kb)
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