Periodic outbursts in the peculiar X-ray binary 2S 0114+65.

Abstract

The peculiar X-ray binary system 2S 0114 + 65 has been observed by every X-ray satellite mission since its discovery by SAS 3 in 1977. A persistent feature of all the observations are outbursts on a time scale of about 3 hr. We have utilized the archival EXOSAT data, as well as published data and ROSAT all-sky survey data and show that the observed outbursts are describable by a 2.78-hr period at all epochs. From the data at hand we determine that the underlying clock mechanism has a Q value not less than 10. The pulse shape is qualitatively similar to those observed in EXO 2030+375 and similar mechanisms may be at work in both systems. We speculate on the intriguing possibility that the underlying clock may be the pulsations of the early B star member of the system, LSI + 65 10. If this hypothesis is the correct description of the system, then LSI + 65 10 should be observed to pulsate optically at the 2.78-hr outburst period, making it a member of the Beta Cephei class of pulsating early B stars.