MACHO Light Curve of IGR J05007-7047
ATel #2601; P. C. Schmidtke (Arizona State University), A. P. Cowley (Arizona State University)
on 8 May 2010; 00:02 UT
Credential Certification: Paul Schmidtke (Paul.Schmidtke@asu.edu)
Subjects: Optical, X-ray, Binary, Neutron Star
Masetti et al. (ATel #783) identified the optical counterpart for X-ray
source IGR J05007-7047 with an LMC star
showing H-alpha emission and other Balmer lines in absorption,
which suggests it may be a Be star. Coe et al. (ATel #2597) have analyzed
this star in the OGLE-III database. We find that it is also
coincident with MACHO star 23.3300.10, whose longterm light curve
shows dips ranging in depth from 0.1 to 0.5 mag every 600-800 days.
At minimum light the color is blue (B-V~-0.15) consistent with a middle B
star. As the source brightens the color becomes redder (B-V~+0.1),
perhaps indicating a growing cool disk.
After flattening the MACHO light curve to remove the longterm
trends, the resulting periodogram shows a peak at ~28 days, consistent with the
X-ray period of 30.77 days (La Parola et al., ATel #2594) and the
OGLE-III period of 30.90 days (Coe et al., ATel #2597). The folded
MACHO R data shows a sinusoidal light curve with a full amplitude of
~0.01 mag.
