Two new intermediate polars with a soft X-ray component

Abstract

Aims. We analyze the first X-ray observations with XMM-Newton of 1RXS J070407.9+262501 and 1RXS 180340.0+401214, in order to characterize their broad-band temporal and spectral properties, also in the UV/optical domain, and to confirm them as intermediate polars.Methods. For both objects, we performed a timing analysis of the X-ray and UV/optical light curves to detect the white dwarf spin pulsations and study their energy dependence. For 1RXS 180340.0+401214 we also analyzed optical spectroscopic data to determine the orbital period. X-ray spectra were analyzed in the 0.2-10.0 keV range to characterize the emission properties of both sources. Results. We find that the X-ray light curves of both systems are energy dependent and are dominated, below 3-5 keV, by strong pulsations at the white dwarf rotational periods (480 s for 1RXS J070407.9+262501 and 1520.5 s for 1RXS 180340.0+401214). In 1RXS 180340.0+401214 we also detect an X-ray beat variability at 1697 s which, together with our new optical spectroscopy, favours an orbital period of 4.4 h that is longer than previously estimated. Both systems show complex spectra with a hard (temperature up to 40 keV) optically thin and a soft (kT ∼ 85-100 eV) optically thick components heavily absorbed by material partially covering the X-ray sources. Conclusions. Our observations confirm the two systems as intermediate polars and also add them as new members of the growing group of "soft" systems which show the presence of a soft X-ray blackbody component. Differences in the temperatures of the blackbodies are qualitatively explained in terms of reprocessing over different sizes of the white dwarf spot. We suggest that systems showing cooler soft X-ray blackbody components also possess white dwarfs irradiated by cyclotron radiation.

Paloma: A Magnetic Cv Between Polars and Intermediate Polars

“…The soft-X-ray excess is mostly prominent in the X-ray spectra of polars; however, the growing number of IPs (e.g., PQ Gem, NY Lup, GK Per, V405 Aur, and V2400 Oph) also shows the soft X-ray component. In many systems, this soft-X-ray excess was explained by the black-body component with a temperature less than 100 eV (e.g., Mason et al 1992;Haberl et al 1994;de Martino et al 2004;Evans & Hellier 2007;Anzolin et al 2008Anzolin et al , 2009). However, in an IP IGR J17195−4100 the soft-X-ray excess was well fitted by a low-temperature apec component in X-ray spectra (Girish & Singh 2012).…”

SUZAKUOBSERVATION OF THE CLASSICAL NOVA V2491 Cyg IN QUIESCENCE

“…On the other hand, a distinct blackbody component with temperature in the range 20-100 eV, heavily absorbed by dense material partially covering the X-ray source, is observed in many IPs (Evans & Hellier 2007;Anzolin et al 2008;Bernardini et al 2012, and references therein). These objects form a growing group of so-called "soft IPs", including fifteen confirmed IPs (Bernardini et al 2012).…”

“…This phenomenon is usually caused by the accretion curtains crossing the line of sight (Evans & Hellier 2007;Anzolin et al 2008). …”

Swift J201424.9+152930: discovery of a new deeply eclipsing binary with 491-s and 3.4-h modulations

“…Ishida, Mukai, & Osborne 1994;Beardmore, Osborne, & Hellier 2000) and in many cases by a soft blackbody component with temperatures of tens of eV (e.g. de Martino et al 2004;Anzolin et al 2008Anzolin et al , 2009). On the other hand, X-ray spectra of quiescent NS low mass, short-period systems are characterized by a soft blackbody component arising from the NS atmosphere but also with lower temperature than that derived.…”