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Session 36 - Extragalactic X-Ray Sources.
Display session, Tuesday, January 14
We present the results of ASCA observations of a sample of LINERs and low-luminosity AGN (LLAGN). We find that in most cases the ASCA spectra can be described by a canonical model consisting of a power-law with a photon index, \Gamma \sim 1.7-2.0, plus a soft optically-thin emission component with kT \sim 0.6-0.8 keV. The implied element abundances are often sub-solar. The soft component is usually extended and the nuclear, point-like emission is sometimes absorbed by column densities in the range \sim 10^21 - 10^23 \ cm^-2. The relative luminosities of the soft and hard components vary from galaxy to galaxy. The 2-10 keV luminosity of the hard component is typically \sim 10^40-41 \ ergs \ s^-1 whereas the 0.5-2.0 keV luminosity of the soft component is typically \sim 10^39-40 \ ergs \ s^-1. The hard component is similar to the observed X-ray spectra of quasars and also to the intrinsic X-ray spectra of classical Seyfert galaxies. Most of the galaxies in our sample exhibit no significant (\Delta I/I > 20%) short-term variability (with timescales of a day or less) whereas long-term variability is common. Most of the galaxies in our sample have L_X/L_H\alpha ratios comparable to those of more luminous AGN. These results suggest a strong connection between classical AGN, LINERs, and starburst galaxies.
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