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

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

Corresponding author: J. M. Bonnet-Bidaud, bobi@discovery.saclay.cea.fr

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 N_H 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.