Abstract
INAF IASF-Bo, via Gobetti 101, 40129 Bologna, ItalyABSTRACTAims.We investigate the X-ray spectral and timing properties of the high mass X-ray binary EXO 2030+375 observed during itsJune–September 2006 giant (type II) outburst.Methods.The data analyzed in this work are from partly simultaneous observations with INTEGRALand Swift. The pulse period Pand its temporal derivative P˙ are measured. X-ray pulse profiles in different energy ranges and time intervals are constructed. Pulseaveraged 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 giantoutburst when the source was discovered. The value of P˙ is found to be linearly related to the X-ray luminosity of thesource duringthe outburst. For the first time the hard X-ray (> 25 keV) characteristics of the source during a type II outburst are studied. The X-raypulse profiles apparently change with luminosity. The X-ray spectral continuum in the 3–120 keV energy range is modeled with anabsorbed power law with an exponential cutoff around E ∼ 26 keV. An iron emission line at ∼6–7 keV is observed. The spectrumreveals some features between 10 and 20 keV which can be modeled either by a broad emission line at ∼13–15 keV (a “bump”) or bytwo absorption lines at ∼10 and ∼20 keV.Key words. X-ray binaries; neutron stars; accretion disks
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