Optical identification of Swift J0732.5-1331
ATel #760; T. Marsh (Warwick), S. Littlefair (Sheffield), V. Dhillon (Sheffield)
on 8 Mar 2006; 19:38 UT
Credential Certification: Tom Marsh (tom.marsh@warwick.ac.uk)
Subjects: Optical, X-ray, Cataclysmic Variable
On 7 March 2006 we looked at the proposed optical counterpart of the hard X-ray source Swift J0732.5-1331 (Atel #697, #735, #757) using the high-speed multi-band CCD camera ULTRACAM mounted on the 4.2m William Herschel Telescope. This star is a suspected intermediate polar. We detected the pulsations previously reported in Atel #757. However, we also found that the proposed counterpart resolves into two stars approximately 1.8" apart and lying along a North-East/South-West axis. The pulsating source is the North-East star of the pair and was approximately half as bright as its companion in g', but equally bright in u'. The source confusion probably explains the puzzling reports of domination by a G star without any ellipsoidal variations and changes in its optical spectrum (Atel #735 and #757). The G star is presumably the South-West star of the pair and is nothing to do with the X-ray source.
