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Two new intermediate polars with a soft X-ray component

Authors :
Anzolin, G.
de Martino, D.
Bonnet-Bidaud, J.-M.
Mouchet, M.
G?nsicke, B.
Matt, G.
Mukai, K.
Source :
Astronomy and Astrophysics; October 2008, Vol. 489 Issue: 3 p1243-1254, 12p
Publication Year :
2008

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.

Details

Language :
English
ISSN :
00046361 and 14320746
Volume :
489
Issue :
3
Database :
Supplemental Index
Journal :
Astronomy and Astrophysics
Publication Type :
Periodical
Accession number :
ejs16962351