Megan C. Engel, Craig O. Heinke, Gregory R. Sivakoff, Khaled G. Elshamouty, Peter D. Edmonds
We present a candidate orbital period for the low mass X-ray binary XB
1832-330 in the globular cluster NGC 6652 using a 6.5 hour Gemini South
observation of the optical counterpart of the system. Light curves in g' and r'
for two LMXBs in the cluster, sources A and B in previous literature, were
extracted and analyzed for periodicity using the ISIS image subtraction
package. A clear sinusoidal modulation is evident in both of A's curves, of
amplitude ~0.11 magnitudes in g' and ~0.065 magnitudes in r', while B's curves
exhibit rapid flickering, of amplitude ~1 magnitude in g' and ~0.5 magnitudes
in r'. A Lomb-Scargle test revealed a 2.15 hour periodic variation in the
magnitude of A with a false alarm probability less than 10^-11, and no
significant periodicity in the light curve for B. Though it is possible
saturated stars in the vicinity of our sources partially contaminated our
signal, the identification of A's binary period is nonetheless robust.
View original:
http://arxiv.org/abs/1201.4131
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