The Orbital Period of the X-ray Pulsar XTE SMC144s
ATel #209; R. H.D. Corbet (GSFC and USRA), S. Laycock (CfA), F. E. Marshall (GSFC), C. B. Markwardt (GSFC and University of Maryland), M. J. Coe (Southampton University)
on 20 Nov 2003; 22:38 UT
Credential Certification: Robin Corbet (corbet@gsfc.nasa.gov)
Subjects: X-ray, Binary, Neutron Star, Transient
We have detected three additional outbursts from the 144s pulse period
transient X-ray pulsar in the direction of the Small Magellanic Cloud with
the RXTE Proportional Counter Array since the outburst that was reported in ATEL #163.
We have continued to monitor the SMC since that time with observations
made at intervals of approximately one week. The first outburst from
"XTE SMC144s" was detected on 2003 May 19 and subsequent outbursts were
detected on July 21, September 22, and November 18. These outbursts are all
consistent with a recurrence period of approximately two months. A linear
fit to these detection times gives
T = MJD 52779.2 (+/- 2.9) + n x 61.2 (+/- 1.6) d
We interpret this outburst recurrence period as the orbital period of a
neutron/Be star binary with outbursts occurring at periastron passage. Due
to the presence of other active pulsars in the SMC it has not yet been
possible to obtain an accurate position for this source.
A list of known X-ray pulsars in the SMC is provided at: http://lheawww.gsfc.nasa.gov/users/corbet/pulsars
X-ray Pulsars in the SMC
