A New Period Analysis of OGLE-III Data for SXP967
ATel #1953; P. C. Schmidtke (Arizona State University), A. P. Cowley (Arizona State University), A. Udalski (Warsaw University Observatory)
on 6 Mar 2009; 20:18 UT
Credential Certification: Paul Schmidtke (Paul.Schmidtke@asu.edu)
Subjects: Optical, X-ray, Binary, Neutron Star, Pulsar
We have analyzed 8 seasons of OGLE-III data for SXP967 (formerly SXP700;
see discussion of the revised pulsar period by Haberl et al., 2008, A&A 489, 327).
The I-band observations show long-term changes of 0.6 mag, which were
removed via polynomial fitting to long segments of data (1-3 seasons in length).
The remaining small-amplitude variations were analyzed using both
periodogram and PDM techniques. The strongest signal, with P=101.94 days,
has an asymmetrical shape (very rapid rise followed by gradual decline over 0.2P)
with an amplitude of nearly 0.1 mag. The recurrence time and shape of these
outbursts suggests they are caused by orbital motion of the Be/pulsar binary.
Examination of inter-outburst data shows strong power in the periodogram at
P=1.003 days. The folded light curve is sinusoidal with full amplitude of ~0.02 mag,
suggesting the variation is due to non-radial pulsations (NRP) of the Be star. These
appear to be stable throughout the observations. An alias of the pulsation period
(at P~258 days) shows less power, and its sinusoidal light curve argues against it
being the orbital period. We note that McGowan et al. (2007, MNRAS 376, 759)
reported a 267-day period using 5 seasons of OGLE-III data, consistent with also
being an alias of the NRP.
