High variability in Vela X-1: giant flares and off states

  title={High variability in Vela X-1: giant flares and off states},
  author={Ingo Kreykenbohm and Joern Wilms and Peter Kretschmar and J M Torrej{\'o}n and Katja Pottschmidt and Manfred Hanke and Andrea Santangelo and Carlo Ferrigno and Ruediger Staubert},
  journal={Astronomy and Astrophysics},
Aims. We investigate the spectral and temporal behavior of the high mass X-ray binary Vela X-1 during a phase of high activity, with special focus on the observed giant flares and off states. Methods. INTEGRAL observed Vela X-1 in a long almost uninterrupted observation for two weeks in 2003 Nov/Dec. The data were analyzed with OSA 7.0 and FTOOLS 6.2. We derive the pulse period, light curves, spectra, hardness ratios, and hardness intensity diagrams, and study the eclipse. Results. In addition… 
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