The intense galactic X-ray source GX 349+2 ( Sco X-2 ) belongs to the class of persistently 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 been optically 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 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 ) .
Recently \markcite SouthSouthwell et al .
( 1996 ) have presented spectroscopic observations of GX 349+2 suggesting a 14 d orbital period .
We have obtained broadband photometry of the system on six consecutive nights , and find a statistically significant 21.85 \pm 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 other Z-sources , caution will be needed to insure that the variations are truly periodic , and not simply due to chaotic variability observed over a relatively short time span .
Depending on the origin of the brightness variations , our proposed period could be either the orbital or half the orbital period .
If our period is confirmed , then the nature of the 14 d spectroscopic variation found by \markcite SouthSouthwell et al .
( 1996 ) is unclear .
There is evidence that the mass function of GX 349+2 is similar to that of Sco X-1 .