A&A 365, L282-L287 (2001)
DOI: 10.1051/0004-6361:20000222

The eclipsing bursting X-ray binary EXO 0748-676 revisited by XMM-Newton

J. M. Bonnet-Bidaud¹, F. Haberl², P. Ferrando¹, P. J. Bennie³ and E. Kendziorra⁴.

¹  Service d'Astrophysique, DSM/DAPNIA/SAp, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
²  Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
³  Department of Physics & Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
⁴  Institut für Astronomie und Astrophysik - Astronomie, University of Tübingen, Waldhäuser Strasse 64, 72076 Tübingen, Germany

(Received 13 October 2000 / Accepted 8 November 2000)

Abstract
The bright eclipsing and bursting low-mass X-ray binary EXO 0748-676 has been observed at several occasions by XMM-Newton during the initial calibration and performance verification (CAL/PV) phase. We present here the results obtained from observations with the EPIC cameras. Apart from several type-I X-ray bursts, the source shows a high degree of variability with the presence of soft flares. The wide energy coverage and high sensitivity of XMM-Newton allows for the first time a detailed description of the spectral variability. The source is found to be the superposition of a central ( 2 10⁸ cm) Comptonized emission, most probably a corona surrounding the inner edge of an accretion disk, associated with a more extended ( 3 10¹⁰ cm) thermal halo at a typical temperature of 0.6 keV with an indication of non-solar abundances. Most of the variations of the source can be accounted for by a variable absorption affecting only the central comptonized component and reaching up to cm^-2. The characteristics of the surrounding halo are found compatible with an irradiated atmosphere of an accretion disc which intercepts the central emission due to the system high inclination.

Key words: stars: individual (EXO 0748-676/UY Vol) - binaries: eclipsing - X-rays: stars - accretion: accretion disc

Offprint request: J. M. Bonnet-Bidaud, bobi@discovery.saclay.cea.fr

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