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

• Published in: Astronomy and astrophysics (Berlin) Vol. 464; no. 3; pp. L45 - L48
• Main Authors: Klochkov, D., Horns, D., Santangelo, A., Staubert, R., Segreto, A., Ferrigno, C., Kretschmar, P., Kreykenbohm, I., La Barbera, A., Masetti, N., McCollough, M., Pottschmidt, K., Schönherr, G., Wilms, J.
• Format: Journal Article
• Language: English
• Published: Les Ulis EDP Sciences 01.03.2007
• Subjects: accretion; accretion disks; Astronomy; Earth, ocean, space; Exact sciences and technology; stars: neutron; X-ray binaries; keV range; Neutron stars; Hard x radiation; accretion, accretion disks; Spectral properties; Binary X ray source; Cosmic x-ray sources; Luminosity; X-ray spectra; Accretion disks; stars: neutron; Continuum; Absorption line; X-ray binary stars; Models; X-ray binaries; Emission line; Timing; Power law; Pulse shape; Simultaneous observation
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20066801

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 $\dot P$ 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 $\dot P$ 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 $E\sim26$ 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.