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1998ApJ...499..650I - Astrophys. J., 499, 650-669 (1998/June-1)
ROSAT X-ray colors and emission mechanisms in early-type galaxies.
IRWIN J.A. and SARAZIN C.L.
Abstract (from CDS):
Galaxies with the lowest LX/LB values appear to be lacking a hot interstellar component. Their X-ray colors are consistent with those derived from the bulges of the spiral galaxies M31 and NGC 1291. In M31, the X-ray emission is resolved into discrete sources and is apparently due primarily to low-mass X-ray binaries (LMXBs). We therefore suggest that the bulk of the X-ray emission in the faintest elliptical galaxies is also due to LMXBs. Previously, the X-ray spectra of X-ray-faint galaxies had been found to be described by a hard component, which was attributed to LMXB emission, and a very soft component of unknown origin. We show that the very soft component also likely results from LMXBs, as a very soft component is seen in the X-ray spectra of the nearby LMXB Her X-1 and LMXBs in the bulge of M31. If the X-ray emission in X-ray-faint galaxies is primarily from stellar sources, then a range in LX/LB among these galaxies suggests that the stellar X-ray luminosity does not scale with optical luminosity, at least for galaxies of low optical luminosities. This could be the result of a decrease in the proportion of LMXBs with decreasing optical luminosity and/or the effects of fluctuations in the small number of LMXBs expected.
Abstract Copyright: ∼
Journal keyword(s): Galaxies: Abundances - Galaxies: Elliptical and Lenticular, cD - Galaxies: Halos - Galaxies: ISM - X-Rays: Galaxies - X-Rays: ISM
Simbad objects: 71
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