The XMM-Newton view of the eclipse and dips of the dwarf nova Z Chamaleontis

作者：Nucita A A^*; Kuulkers E; Maiolo B M T; De Paolis F; Ingrosso G; Vetrugno D

来源：Astronomy & Astrophysics, 2011, 536: A75.

DOI：10.1051/0004-6361/201117572

• X-rays: binaries
• white dwarfs
• novae, cataclysmic variables

Context. A cataclysmic variable contains a white dwarf that accretes material from a secondary star via the Roche lobe mechanism. Systems with high line-of-sight inclination angles offer the possibility to pinpoint the location of the X-ray emitting region by characterizing the observed eclipse by the secondary star.
Aims. We present an XMM-Newton observation of the dwarf nova Z Chamaleontis that we analyzed to determine the properties of the X-ray and optical light curves, as well as the high-energy spectrum.
Methods. We performed a spectral analysis of the data taken by the EPIC camera, and a timing analysis of the observed X-ray and optical OM light curves.
Results. We find that a multi-temperature plasma component absorbed by ionized material is required to describe the data. In particular, we estimate that the total absorbed flux in the 0.2-9.0 keV band is F-0.2-9.0(Abs) = (4.1 +/- 0.1) x 10(-12) erg s(-1) cm(-2), which, when accounted for absorption and bolometric correction, corresponds to a bolometric luminosity of L-X(Bol) = (6.9 +/- 0.1) x 10(30) erg s(-1) at a distance of 97 pc. The mass accretion rate onto the white dwarf turns out to be about 1.1 x 10(-11) M-circle dot yr(-1). Our analysis of the optical and X-ray eclipse light curves and the mid-eclipse times of Z-Chamaleontis, in addition to the eclipse (during which the observed EPIC count rate is 0.033 +/- 0.003 count s(-1)), implies that the X-ray light curve contains dips (at the orbital phases 0.30 +/- 0.02 and 0.73 +/- 0.02) that can be naturally explained as absorption effects by intervening stable gas clouds close to the accretor.

• 出版日期2011-12