1,306 research outputs found
X-ray populations in galaxies
Today's sensistive, high resolution Chandra X-ray observations allow the
study of many populations of X-ray sources. The traditional astronomical tools
of photometric diagrams and luminosity functions are now applied to these
populations, and provide the means for classifying the X-ray sources and
probing their evolution. While overall stellar mass drives the amount of X-ray
binaries in old stellar population, the amount of sources in star-forming
galaxies is related to the star formation rate. Shart-lived, luminous, high
mass binaries (HNXBs) dominate these young populations.Comment: This is a review talk,to be published in the proceedings of the IAU
Symposium 230, Populations of high energy sources in galaxies, held in Dublin
(Ireland), August 15-19, 200
Low-Mass X-ray Binary Populations
Low-mass X-ray binaries (LMXBs) have been studied in the Galaxy since the
beginning of X-ray astronomy. A lot has been learned about these bright X-ray
sources, but significant questions are still open. These questions are related
to the origin and evolution of LMXBs, dynamical evolution in globular clusters
(GC) or evolution of native field binaries, and on how their properties may
depend on those of the parent stellar population. The discovery of several
populations LMXB populations in elliptical galaxies with Chandra gives us tools
to look at these sources in a new way.Comment: Talk given at the meeting Mykonos-2010:"Binary Star Evolution: Mass
Loss, Accretion, and Mergers". Submitted for publication in the proceeding
The Very-Soft X-Ray Emission of X-Ray Faint Early-Type Galaxies
A recent re-analysis of Einstein data, and new ROSAT observations, have
revealed the presence of at least two components in the X-ray spectra of X-ray
faint early-type galaxies: a relatively hard component (kT>1.5 keV), and a very
soft component (kT\sim 0.2-0.3 keV). We address the problem of the nature of
the very soft component, and whether it can be due to a hot interstellar medium
(ISM), or is most likely originated by the collective emission of very soft
stellar sources. To this purpose, hydrodynamical evolutionary sequences for the
secular behavior of gas flows in ellipticals have been performed, and the
results are compared with the observational X-ray data: the very soft component
could be entirely explained with a hot ISM only in galaxies where the depth of
the potential well is quite shallow, otherwise the softest contribution to the
X-ray emission comes certainly from stellar sources. As stellar soft X-ray
emitters, we consider late-type stellar corone, supersoft sources such as those
discovered by ROSAT in the Magellanic Clouds and M31, and RSCVn systems. We
finally present a model for the X-ray emission of NGC4365, to reproduce in
detail the results of the ROSAT pointed observation (PSPC spectrum and radial
surface brightness distribution).Comment: Postscript file, 28 pages. For hardcopy of figures contact
[email protected]. BAP 12-1993-040-DD
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