INTEGRAL and Swift observations of EXO 2030+375 during a giant outburst

Aims. We investigate the X-ray spectral and timing properties of the high mass X-ray binary EXO 2030+375 observed during its June–September 2006 giant (type II) outburst. Methods. The data analyzed in this work are from partly simultaneous observations with INTEGRAL and Swift. The pulse period P and its temporal derivative Ṗ are measured. X-ray pulse profiles in different energy ranges and time intervals are constructed. Pulse averaged X-ray spectra for different time intervals are studied. Results. We report a strong spin-up of the source during the outburst, comparable to that observed in 1985 during the previous giant outburst when the source was discovered. The value of Ṗ is found to be linearly related to the X-ray luminosity of the source during the outburst. For the first time the hard X-ray (> 25 keV) characteristics of the source during a type II outburst are studied. The X-ray pulse profiles apparently change with luminosity. The X-ray spectral continuum in the 3–120 keV energy range is modeled with an absorbed power law with an exponential cutoff around E ∼ 26 keV. An iron emission line at ∼6–7 keV is observed. The spectrum reveals some features between 10 and 20 keV which can be modeled either by a broad emission line at ∼13–15 keV (a “bump”) or by two absorption lines at ∼10 and ∼20 keV.