Optical Counterpart of XTE J0103-728 (SXP6.85)
ATel #1181; P. C. Schmidtke (ASU) and A. P. Cowley (ASU)
on 14 Aug 2007; 20:46 UT
Credential Certification: Paul Schmidtke (Paul.Schmidtke@asu.edu)
Subjects: Optical, X-ray, Binary, Neutron Star, Variables, Pulsar
Referred to by ATel #: 7498
Variability of the optical counterpart of the 6.85 s pulsar XTE
J0103-728, whose position is given in ATel #1095, has been studied.
The X-ray source is coincident with MACHO 206.16768.5 and OGLE-II
smc_sc9_146936. Both data sets show the source has a `swooping'
lightcurve, varying over half a magnitude, with a recurrence time of
~658 days. The maximum brightness is fairly constant (I_max=14.5),
while MACHO data show the depth of minima decreased over the 7.5 years
of observations. The color varies through the cycle, with the source
being bluest (V-R=-0.15) at minimum light and reddest (V-R=+0.08)
approximately 100 days after maximum light.
After removing this longterm variation from the I data, we find a weak
periodicity at P=24.82 days. The folded light curve shows an `outburst'
of ~0.02 mag lasting about 0.2P. This could be the orbital period, but
confirmation with X-ray or radial velocity data is needed.