Volume 420, Number 1, June II 2004
|Page(s)||273 - 281|
|Section||Stellar structure and evolution|
|Published online||14 May 2004|
XMM-Newton observations of the dwarf nova YZ Cnc in quiescence
Observatory, PO Box 14, 00014 University of Helsinki, Finland
2 Mullard Space Science Lab, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
3 Department of Physics & Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
4 Institute of Space Applications and Remote Sensing, National Observatory of Athens, PO Box 20048, Athens 11810, Greece
5 Institute of Astronomy & Astrophysics, National Observatory of Athens, PO Box 20048, Greece
Corresponding author: P. Hakala, email@example.com
Accepted: 4 March 2004
We present results from the XMM-Newton observations of the dwarf nova YZ Cnc in a quiescent state. We have performed a detailed time series analysis of the resulting light curves. Unusually, we do not detect any orbital modulation in the UV, with only marginal evidence for X-ray modulation on this period. Although there are peaks in the X-ray periodograms at periods less than 5000 s, we attribute them to red noise effects and assign significance to them using a novel approach. The variability in the UV and optical bands can also be modelled as a result of aperiodic variability (red noise) in the system. There is evidence that the UV and X-ray fluxes are anti-correlated with a time delay of about 100 s, with the UV lagging behind the X-ray emission. This anti-correlation is intriguing, but is only present on two occasions lasting several 1000 s each. The X-ray spectrum shows similar emission features to other dwarf novae and is well fitted using a multi-temperature emission model. We measure a relatively high X-ray luminosity of ergs/s, although this is consistent with a low binary inclination. Finally, we find evidence for a possible -1200 km s-1 blue shift in the fitted Fe K line energies, possibly indicating the presence of an outflow in this low inclination system.
Key words: accretion, accretion disks / stars: individual: YZ Cnc / stars: binaries: close / X-rays: stars / methods: data analysis
© ESO, 2004
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