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XMM-Newton observations of UW CrB -- detection of X-ray bursts and evidence for accretion disc evolution

P. Hakala·G. Ramsay·P. Muhli·P. Charles·D. Hannikainen·K. Mukai·O. Vilhu
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Abstract

UW CrB (MS1603+2600) is a peculiar short period X-ray binary that exhibits extraordinary optical behaviour. The optical light curve shape 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 {\it 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 (ADC) system located at a distance of at least 5--7 kpc, (3--5 kpc above the galactic plane). The X-ray and optical monitor (UV+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 which periodically obscures the optical and soft X-ray emission. This is also supported by the changes in phase-resolved X-ray spectra.

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P. Hakala, G. Ramsay, P. Muhli, P. Charles, D. Hannikainen, K. Mukai, O. Vilhu. 2004-10-25. XMM-Newton observations of UW CrB -- detection of X-ray bursts and evidence for accretion disc evolution. https://doi.org/10.1111/j.1365-2966.2004.08543.x

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