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Session 44 - Stellar X-Ray Sources.
Display session, Tuesday, January 14
Metropolitan Ballroom,

[44.04] Optical and Infrared Photometry of Faint Low Mass X-ray Binary Systems

S. Wachter (U. of Washington)

The intense galactic X-ray source GX 349+2 belongs to the class of persistently bright low mass X-ray binaries called Z-sources. Of the six known Z-sources, only two (\mboxSco X-1 and Cyg X-2) have been studied in the optical. It has been suggested that Z-sources as a group are characterized by evolved companions and correspondingly long orbital periods (Sco X-1, P=0.8 d; Cyg X-2, P=9.8 d). GX 349+2 has only recently been optically identified with a 19th magnitude star. We previously reported on photometric evidence for a 22 h period. Additional observations obtained on 6 consecutive nights in July 1996 confirm this period and refine its value to 22.4 h.

X1608-52 is one of only a few recurrent soft X-ray transients which exhibit persistent X-ray emission between outbursts. Observations of the field after the recent X-ray outburst (IAUC 6331, 6336) show that the faint optical counterpart QX Nor last seen in 1977 has reappeared. Data from May-July 1996, 3-5 months after the outburst, show the counterpart at about R=19.9 and variable on timescales of days. A comparison to identical observations last year shows that the object has brightened by at least 2 mag in R. We also detected QX Nor in the IR in BOTH quiescence and outburst. A faint source is visible at J but not R in May 1995. J frames obtained in August 1996 show the star brighter by about 0.8 mag (J\approx 17).

GX 13+1 is a bright X-ray burst source, located in the galactic bulge. Due to the heavy obscuration in the galactic center direction, no optical counterpart brighter than R\sim 22 mag has been detected, although recently a K=12 IR counterpart was found. Our previous photometry suggests variability of \sim0.4 mag on a timescale of several days. Results of a recent photometric monitoring program will be presented.

Program listing for Tuesday