Broad-band properties of the hard X-ray cataclysmic variables IGR J00234+6141 and 1RXS J213344.1+510725*
Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 3, 35122 Padova, Italy e-mail: email@example.com
2 INAF - Osservatorio Astronomico di Capodimonte, salita Moiariello 16, 80131 Napoli, Italy e-mail: firstname.lastname@example.org
3 CEA Saclay, DSM/DAPNIA/Service d'Astrophysique, 91191 Gif-sur-Yvette, France e-mail: [mfalanga;bonnetbidaud]@cea.fr
4 CRESST and X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA and Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA e-mail: email@example.com
5 Laboratoire APC, Université Denis Diderot, 10 rue Alice Domon et Léonie Duquet, 75005 Paris, France and LUTH, Observatoire de Paris, Section de Meudon, 5 place Jules Janssen, 92195 Meudon, France e-mail: firstname.lastname@example.org
6 Department of physics, Saitama University, Saitama, Japan e-mail: email@example.com
7 Institute of Space and Astronautical Science, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8150, Japan e-mail: firstname.lastname@example.org
Accepted: 25 April 2009
Context. A significant number of cataclysmic variables have been detected as hard X-ray sources in the INTEGRAL survey, most of them of the magnetic intermediate polar type.
Aims. We present a detailed X-ray broad-band study of two new sources, IGR J00234+6141 and 1RXS J213344.1+510725, that allow us to classify them as secure members of the intermediate polar class.
Methods. Timing and spectral analysis of IGR J00234+6141 are based on an XMM-Newton observation and INTEGRAL publicly available data. For 1RXS J213344.1+510725, we use XMM-Newton and Suzaku observations at different epochs, as well as INTEGRAL publicly available data.
Results. We determine a spin period of 561.64 ± 0.56 s for the white dwarf in IGR J00234+6141. The X-ray pulses are observed up to keV. From XMM-Newton and Suzaku observations of 1RXS J213344.1+510725, we find a rotational period of 570.862 ± 0.034 s. The observations span three epochs where the pulsation is observed to change at different energies both in amplitude and shape. In both objects, the spectral analysis spanned over a wide energy range, from 0.3 to 100 keV, shows the presence of multiple emission components absorbed by dense material. The X-ray spectrum of IGR J00234+6141 is consistent with a multi-temperature plasma with a maximum temperature of keV. In 1RXS J213344.1+510725, multiple optically thin components are inferred, as well as an optically thick (blackbody) soft X-ray emission with a temperature of eV. This adds 1RXS J213344.1+510725 to the growing group of soft X-ray intermediate polars.
Conclusions. Though showing similar rotational periods and being hard X-ray sources, these two intermediate polars appear different in several respects, among which the presence of a soft X-ray component in 1RXS J213344.1+510725. This source also emits circularly polarized light in the optical band, thus joining the group of soft and polarized intermediate polars as a fifth member. How the hard X-ray and polarized emission are thermalized in these systems is a timely question.
Key words: stars: binaries: close / stars: individual: IGR J00234+6141 / stars: individual: 1RXS J213344.1+510725 / stars: novae, cataclysmic variables / X-rays: stars / accretion, accretion disks
Based on observations obtained with XMM-Newton and INTEGRAL, ESA science missions with instruments and contributions directly funded by ESA Member States and NASA, and with Suzaku, a Japan's mission developed at the Institute of Space and Astronautical Science of Japan Aerospace Exploration Agency in collaboration with US (NASA/GSFC, MIT) and Japanese institutions.
© ESO, 2009