Optical Sources Near the Bright X-Ray Source in NGC 1073
  New HST observations show that the bright X-ray source in the face-on spiral galaxy NGC 1073 is located near a ring of recent star formation with an age of 8-16 Myr. This strengthens the association of X-ray sources in spiral galaxies emitting near or above the Eddington limit for a 20 solar mass black hole with recent star formation events. Two candidate optical counterparts of the X-ray source are found. The X-ray to optical flux ratios of both are consistent with those of low-mass X-ray binaries and higher than most high-mass X-ray binaries, suggesting that reprocessing of X-rays contributes to the optical light. The optical magnitude and color of one candidate is consistent with that predicted for an X-ray binary with an initial donor mass of 6-8 solar masses. However, the same X-ray binary evolution model underestimates the X-ray luminosity. An X-ray source list for the field is presented which includes detections of the nucleus of NGC 1073, three quasars, and an M3e brown dwarf star with high proper motion. 
Philip Kaaret