EVIDENCE OF X-RAY PERIODICITY IN LSI-DEGREES-303(61)

We have carried out a period analysis of 2-10 keV observations of the 26.5 d radio periodic X-ray binary LSI+61 degrees 303 retrieved from t he quick-look results database provided by the ASM/RXTE team. After ap plying different period search methods, we find evidence that X-ray ou tbursts in LSI+61 degrees 303 are very likely to recur with the same r adio outburst period. Our best estimate of the LSI+61 degrees 303 X-ra y period is 26.7 +/- 0.2 d. The folded X-ray light curve displays a fr actional change in flux by a factor of similar to 5 and its highest em ission level overlaps with the active state of the radio emission.