Search Publications
On stellar limb darkening and exoplanetary transits
Howarth, Ian D.
This paper examines how to compare stellar limb-darkening coefficients evaluated from model atmospheres with those derived from photometry. Different characterizations of a given model atmosphere can give quite different numerical results (even for a given limb-darkening 'law'), while light-curve analyses yield limb-darkening coefficients that are…
Planck early results. XXVI. Detection with Planck and confirmation by XMM-Newton of PLCK G266.6-27.3, an exceptionally X-ray luminous and massive galaxy cluster at z ~ 1
Böhringer, H.; Kneissl, R.; Dahle, H. +189 more
We present first results on PLCKG266.6-27.3, a galaxy cluster candidate detected at a signal-to-noise ratio of 5 in the Planck All Sky survey. An XMM-Newton validation observation has allowed us to confirm that the candidate isa bona fide galaxy cluster. With these X-ray data we measure an accurate redshift, z = 0.94 ± 0.02, and estimate the clust…
Structure and Evolution of Debris Disks Around F-type Stars. I. Observations, Database, and Basic Evolutionary Aspects
Apai, D.; Pascucci, I.; Kovács, J. +11 more
Although photometric and spectroscopic surveys with the Spitzer Space Telescope remarkably increased the number of well-studied debris disks around A-type and Sun-like stars, detailed analyses of debris disks around F-type stars remained less frequent. Using the MIPS camera and the Infrared Spectrograph (IRS) spectrograph, we searched for debris d…
Lyα Emitting Galaxies as Early Stages in Galaxy Formation
Cowie, Lennox L.; Barger, Amy J.; Hu, Esther M.
We present optical spectroscopy of two samples of Galaxy Evolution Explorer grism selected Lyα emitters (LAEs): one at z = 0.195-0.44 and the other at z = 0.65-1.25. We have also observed a comparison sample of galaxies in the same redshift intervals with the same UV magnitude distributions but with no detected Lyα. We use the optical spectroscopy…
The Wolf-Rayet Content of M33
Massey, Philip; Neugent, Kathryn F.
Wolf-Rayet (WR) stars are evolved massive stars, and the relative number of WC-type and WN-type WRs should vary with metallicity, providing a sensitive test of stellar evolutionary theory. The observed WC/WN ratio is much higher than that predicted by theory in some galaxies but this could be due to observational incompleteness for WN types, which…
Embedded current sheets in the Earth’s magnetotail
Malova, H. V.; Petrukovich, A. A.; Zelenyi, L. M. +3 more
In this investigation we introduce and discuss quantitative parameters of a thin current sheet embedded in the background plasma sheet. We use Cluster statistics and empirical models, as well as self-consistent simulations, to understand the formation and development of embedded current sheets, in particular in the course of substorms. Data and th…
Dynamical versus stellar masses of ultracompact dwarf galaxies in the Fornax cluster
Mieske, Steffen; Infante, Leopoldo; Hilker, Michael +1 more
The origin of ultracompact dwarf (UCD) galaxies, compact extragalactic stellar systems, is still a puzzle for present galaxy formation models. We present the comprehensive analysis of high-resolution multi-object spectroscopic data for a sample of 24 Fornax cluster UCDs obtained with VLT with Fibre Large Array Multi Element Spectrograph (FLAMES). …
Constraints on Lorentz Invariance Violation using integral/IBIS observations of GRB041219A
Covino, S.; Götz, D.; Laurent, P. +2 more
One of the experimental tests of Lorentz invariance violation is to measure the helicity dependence of the propagation velocity of photons originating in distant cosmological obejcts. Using a recent determination of the distance of the gamma-ray burst GRB 041219A, for which a high degree of polarization is observed in the prompt emission, we are a…
Multiwavelength campaign on Mrk 509. III. The 600 ks RGS spectrum: unravelling the inner region of an AGN
Kaastra, J. S.; Kriss, G. A.; Arav, N. +14 more
We present the results of our 600 ks RGS observation as part of the multiwavelength campaign on Mrk 509. The very high quality of the spectrum allows us to investigate the ionized outflow with an unprecedented accuracy due to the long exposure and the use of the RGS multipointing mode. We detect multiple absorption lines from the interstellar medi…
A Hubble Space Telescope Study of Lyman Limit Systems: Census and Evolution
Lehner, Nicolas; Howk, J. Christopher; Ribaudo, Joseph
We present a survey for optically thick Lyman limit absorbers at z < 2.6 using archival Hubble Space Telescope observations with the Faint Object Spectrograph and Space Telescope Imaging Spectrograph. We identify 206 Lyman limit systems (LLSs), increasing the number of cataloged LLSs at z < 2.6 by a factor of ~10. We compile a statistical sa…