Ramsay, G., Groot, P. J., Marsh, T. R., Nelemans, G., Steeghs, D. and Hakala, P. (2006) XMM-Newton observations of AM CVn binaries : V396 Hya and SDSS J1240–01. Astronomy & Astrophysics, Vol.457 (No.2). pp. 623-627. doi:10.1051/0004-6361:20065491

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Abstract

We present the results of XMM-Newton observations of two AM CVn systems - V396 Hya and SDSS J1240-01. Both systems are detected in X-rays and in the UV: neither shows coherent variability in their light curves. We compare the rms variability of the X-ray and UV power spectra of these sources with other AM CVn systems. Apart from ES Cet, AM CVn sources are not strongly variable in X-rays, while in the UV the degree of variability is related to the systems apparent brightness. The X-ray spectra of V396 Hya and SDSS J1240-01 show highly non-solar abundances, requiring enhanced nitrogen to obtain good fits. We compare the UV and X-ray luminosities for 7 AM CVn systems using recent distances. We find that the X-ray luminosity is not strongly dependent upon orbital period. However, the UV luminosity is highly correlated with orbital period with the UV luminosity decreasing with increasing orbital period. We expect that this is due to the accretion disk making an increasingly strong contribution to the UV emission at shorter periods. The implied luminosities are in remarkably good agreement with predictions.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Cataclysmic variable stars, White dwarf stars, X-ray sources, Galactic
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Official Date:	October 2006
Dates:	Date Event October 2006 Published
Volume:	Vol.457
Number:	No.2
Page Range:	pp. 623-627
DOI:	10.1051/0004-6361:20065491
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	European Space Agency (ESA), United States. National Aeronautics and Space Administration (NASA), Suomen Akatemia [Academy of Finland], Smithsonian Astrophysical Observatory, Nederlandse Organisatie voor Wetenschappelijk Onderzoek [Netherlands Organisation for Scientific Research] (NWO), Particle Physics and Astronomy Research Council (Great Britain) (PPARC)
Grant number:	NNG04G30G (NASA), NNG06GC05G (NASA), 639.042.201 (NWO), 639.041.405 (NWO)

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