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The intense galactic X-ray source GX 349+2 (Sco X-2) belongs to the class ofpersistently bright low-mass X-ray binaries called Z-sources. GX 349+2,although observed in X-rays for more than 30 years, has only recently beenoptically identified with a 19th mag star. Of the six known Z-sources, only two(Sco X-1 and Cyg X-2) have been studied in the optical. It has been suggestedthat Z-sources as a group are characterized by evolved companions andcorrespondingly long orbital periods (Sco X-1, P=0.8 d; Cyg X-2, P=9.8 d).Recently Southwell et al. (1996) have presented spectroscopic observations ofGX 349+2 suggesting a 14 d orbital period. We have obtained broadbandphotometry of the system on six consecutive nights, and find a statisticallysignificant 21.85 +/- 0.4 h (3 sigma) period of 0.14 mag half-amplitude,superposed on erratic flickering typical of Sco X-1 type objects. As with otherZ-sources, caution will be needed to insure that the variations are trulyperiodic, and not simply due to chaotic variability observed over a relativelyshort time span. Depending on the origin of the brightness variations, ourproposed period could be either the orbital or half the orbital period. If ourperiod is confirmed, then the nature of the 14 d spectroscopic variation foundby Southwell et al. (1996) is unclear. There is evidence that the mass functionof GX 349+2 is similar to that of Sco X-1.Comment: 17 pages including 3 tables and 5 figures; Uses AASTeX 4.0; Accepted  for publication in The Astronomical Journal, volume 112, December 199

Photometry of GX 349+2: Evidence for a 22-Hour Period