The broad-band X-ray spectrum of the dipping low mass X-ray binary EXO 0748–676

We present results of a 0.1–100 keV BeppoSAX observation of the dipping low-mass X-ray binary (LMXRB) EXO 0748–676 performed in 2000 November. During the observation EXO 0748–676 exhibited X-ray eclipses, type I X-ray bursts and dipping activity over a wide range of orbital phases. The 0.1–100 keV “dip-free”(i.e. dipping and eclipsing intervals excluded) spectrum is complex, especially at low energies where a soft excess is present. Two very different spectral models give satisfactory fits. The first is the progressive covering model, consisting of separately absorbed black body and cut-off power law components. This model is often used to study the dipping activity in LMXRB. The second model is an absorbed cut-off power law together with a moderately ionized absorber with a sub-solar abundance of Fe and a 2.13 keV absorption feature (tentatively identified with Si xii