XMM–Newton observations of UW CrB: detection of X-ray bursts and evidence for accretion disc evolution |
| |
| Authors: | Pasi Hakala Gavin Ramsay Panu Muhli Phil Charles Diana Hannikainen Koji Mukai Osmi Vilhu |
| |
| Institution: | Observatory, PO Box 14, University of Helsinki, FIN-00014 University of Helsinki, Finland;Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT;School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ;Laboratory for High Energy Astrophysics, NASA/GSFC, Code 662, Greenbelt, MD 20771, USA |
| |
| Abstract: | UW CrB (MS 1603+2600) is a peculiar short-period X-ray binary that exhibits extraordinary optical behaviour. The shape of the optical light curve of the system changes drastically from night to night, without any changes in overall brightness. Here we report X-ray observations of UW CrB obtained with XMM–Newton . We find evidence for several X-ray bursts, confirming a neutron star primary. This considerably strengthens the case that UW CrB is an accretion disc corona system located at a distance of at least 5–7 kpc (3–5 kpc above the Galactic plane). The X-ray and Optical Monitor (ultraviolet–optical) light curves show remarkable shape variation from one observing run to another, which we suggest are due to large-scale variations in the accretion disc shape resulting from a warp that periodically obscures the optical and soft X-ray emission. This is also supported by the changes in phase-resolved X-ray spectra. |
| |
| Keywords: | accretion accretion discs binaries: close stars: individual: UW CrB X-rays: binaries X-rays: bursts |
|
|
