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

• Published in: Astronomy and astrophysics (Berlin) 2001-01, Vol.365 (1), p.L282-L287
• Main Authors: Bonnet-Bidaud, J. M., Haberl, F., Ferrando, P., Bennie, P. J., Kendziorra, E.
• Format: Article
• Language: English
• Subjects: accretion: accretion disc; Astrophysics; binaries: eclipsing; Cosmology and Extra-Galactic Astrophysics; Physics; stars: individual (EXO 0748-676/UY Vol); X-rays: stars
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361:20000222

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 NH $\sim 1.3 10^{23}$ 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.