The optical counterpart of XTE J0929-314: the third transient millisecond X-ray pulsar
Abstract
A blue and variable optical counterpart of the X-ray transient XTE J0929-314 was identified on 2002 May 1. We conducted frequent BVRI broad-band photometry on this object using the Mt Canopus 1-m telescope during May and June until it had faded to below 21st magnitude. Nearly continuous I-band CCD photometry on 2002 May 2-4 revealed a ~10 per cent sinusoidal modulation at the binary period lasting ~6 cycles during the latter half of May 2. The phase indicates that the modulation may be due to a combination of emission by a hotspot on the disc and X-ray heating of the secondary. The emission generally trended bluer with B-I decreasing by 0.6 mag during the observations, but there were anomalous changes in colour during the first few days after optical identification when the I-band flux decreased slightly while fluxes in other bands increased. Spectral analysis of the BVRI broad-band photometry shows evidence of a variable excess in the R and I bands. We suggest that this may be due to synchrotron emission in matter flowing out of the system, and note that similar processes may have been responsible for anomalous V- and I-band measurements in 1998 of the persistent millisecond X-ray pulsar SAX J1808.4-3658.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2005
- DOI:
- 10.1111/j.1365-2966.2005.09255.x
- arXiv:
- arXiv:astro-ph/0506295
- Bibcode:
- 2005MNRAS.361.1180G
- Keywords:
-
- binaries close;
- pulsars general;
- pulsars individual XTE J0929-314;
- stars low-mass;
- stars neutron;
- X-rays binaries;
- Astrophysics
- E-Print:
- 7 pages, 6 figures, accepted by MNRAS, 6 June 2005