X-ray spectroscopy and photometry of the long-period polar AI Tri with XMM-Newton

Abstract

Context. The energy balance of cataclysmic variables with strong magnetic fields is a central subject in understanding accretion processes on magnetic white dwarfs. With XMM-Newton, we perform a spectroscopic and photometric study of soft X-ray selected polars during their high states of accretion. Aims. On the basis of X-ray and optical observations of the magnetic cataclysmic variable AI Tri, we derive the properties of the spectral components, their flux contributions, and the physical structure of the accretion region in soft polars. Methods. We use multi-temperature approaches in our xspec modeling of the spectra to describe the physical conditions and the structures of the post-shock accretion flow and the accretion spot on the white-dwarf surface. In addition, we investigate the accretion geometry of the system by a timing analysis of the photometric data. Results. Flaring soft X-ray emission from the heated surface of the white dwarf dominates the X-ray flux during roughly 70% of the binary cycle. This component deviates from a single black body and can be described by a superimposition of mildly absorbed black bodies with a Gaussian temperature distribution. In addition, weaker hard X-ray emission is visible nearly all the time. The spectrum from the cooling post-shock accretion flow is most closely fitted by a combination of thermal plasma mekal models with temperature profiles adapted from prior stationary two-fluid hydrodynamic calculations. The soft X-ray light curves show a dip during the bright phase, which can be interpreted as self-absorption in the accretion stream. Phase-resolved spectral modeling supports the picture of one-pole accretion and self-eclipse. One of the optical light curves corresponds to an irregular mode of accretion. During a short XMM-Newton observation at the same epoch, the X-ray emission of the system is clearly dominated by the soft component.

A&A, in press; 11 pages, 9 figures, 3 tables

References in corpus (4)

• Establishing HZ43 A, Sirius B, and RX J185635-3754 as soft X-ray standards: a cross-calibration between the Chandra LETG+HRC-S, the EUVE spectrometer, and the ROSAT PSPC
• Statistical evaluation of the flux cross-calibration of the XMM-Newton EPIC cameras
• The serendipituous discovery of a short-period eclipsing polar in 2XMMp
• XMM-Newton observations of the eclipsing polar V2301 Oph

Cited by in corpus (8)

• Quasi-periodic oscillations in accreting magnetic white dwarfs I. Observational constraints in X-ray and optical
• The NuSTAR Hard X-ray Survey of the Norma Arm Region
• A new soft X-ray spectral model for polars with an application to AM Herculis
• Multiwavelength study of RX J2015.6+3711: a magnetic cataclysmic variable with a 2-hr spin period
• Confirmation of two magnetic cataclysmic variables as polars: 1RXS J174320.1-042953 and YY Sex
• Phase-resolved X-ray spectroscopy and spectral energy distribution of the X-ray soft polar RS Caeli
• Discovery, observations and modelling of a new eclipsing polar: MASTER OT J061451.70-272535.5
• XMM-Newton observations of the X-ray soft polar QS Telescopii