Optical Period of the Newly Discovered X-ray Pulsar CXOU J005758.4-722229
ATel #5556; P. C. Schmidtke, A. P. Cowley (Arizona State University)
on 6 Nov 2013; 19:49 UT
Credential Certification: Paul Schmidtke (Paul.Schmidtke@asu.edu)
Subjects: Optical, X-ray, Binary, Pulsar
Israel et al. (ATel #5552) reported the discovery of a new transient X-ray pulsar in the Small Magellanic Cloud with a pulsation period of P=7.918s (SXP7.92).
Using OGLE-II data we find the likely optical counterpart to be star 46134 in field SMC_SC8 with a mean I magnitude of 15.8. In the first OGLE-II season the source brightened from 15.85 to 15.7 with
clear outbursts every 40.03 days. The outbursts show a steep rise and slower decline, with a full amplitude of ~0.04 mag. The folded light curve reveals a dip in brightness just before maximum light, as is seen in SXP291 (Schmidtke et al. 2013, MNRAS 431, 252). This 40-day period is very likely to be the orbital period of SXP7.92.
In the following three OGLE-II seasons the system was fainter (I=15.9) and showed a fairly constant magnitude. No clear periodicity was present in this fainter state.
