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M. R. Garcia (Harvard-Smithsonian CfA)
Between Oct 1999 and Jun 2001 Chandra observed M31 on a nearly monthly schedule. These observations allowed the discovery of 14 X-ray transients, a few of which were followed up with HST in an attempt to find contemporaneous optical counterparts. The transient most luminous in X-rays shows a possible U~23 counterpart in HST imaging. The ratio of the X-ray to optical luminosity implies a rather long orbital period for this transient.
By adding the Chandra observations together we are able to measure the luminosity function within the bulge region down to ~3 \times 1035erg~s-1. This luminosity function shows a break whose position increases monotonically as we move out from the bulge into the disk. The slope of the luminosity function becomes steeper as we move towards the disk, which is surprising given that elliptical galaxies tend to have steeper luminosity functions than spiral disks. A hint as to what is causing this surprising behavior may be found in the variability of sources with M31, which also shows a monotonic trend, decreasing with increasing radius.
This work supported in part by NASA grant GO-9087 and contract NAS8-38248.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.