机译:Why are X-ray sources in the M31 bulge so close to planetary nebulae?
Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA;
astrometry; galaxies : individual (M31); planetary nebulae : general; supernova remnants; X-rays : general; LARGE MAGELLANIC CLOUD; HIGH-RESOLUTION CAMERA; SUPERNOVA-REMNANTS; GLOBULAR-CLUSTERS; INTERSTELLAR-MEDIUM; POINT SOURCES; ROSAT OBSERVATIONS; ANDROMEDA GALAXY; STANDARD CANDLES; STAR-CLUSTERS;