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Preprint 10/11

Quasi-periodic flares in EXO 2030+375 observed with INTEGRAL

D. Klochkov (1), C. Ferrigno (2), A. Santangelo (1), R. Staubert (1), P. Kretschmar (3), I. Caballero (4), K. Postnov (5), and C. A. Wilson-Hodge (6)

(1) Institut für Astronomie und Astrophysik, Universität Tübingen (IAAT), Sand 1, 72076 Tübingen, Germany
(2) ISDC Data Center for Astrophysics of the University of Geneva chemin d’Ecogia, 16 1290 Versoix, Switzerland
(3) European Space Astronomy Centre (ESA/ESAC), Science Operations Department, Villanueva de la Canada (Madrid), Spain
(4) CEA Saclay, DSM/IRFU/SAp-UMR AIM (7158) CNRS/CEA/Universite; P. Diderot F-91191
(5) Sternberg Astronomical Institute, Universitetski pr. 13, Moscow, 119991, Russia
(6) NASA Marshall Space Flight Center, Huntsville, AL 35812, USA

To be published in: A&A Letters

Abstract. Context: Episodic flaring activity is a common feature of X-ray pulsars in HMXBs. In some Be/X-ray binaries flares were observed in quiescence or prior to outbursts. EXO 2030+375 is a Be/X-ray binary showing "normal" outbursts almost every ~46 days, near periastron passage of the orbital revolution. Some of these outbursts were occasionally monitored with the INTEGRAL observatory. Aims: The INTEGRAL data revealed strong quasi-periodic flaring activity during the rising part of one of the system's outburst. Such activity has previously been observed in EXO 2030+375 only once, in 1985 with EXOSAT. (Some indications of single flares have also been observed with other satellites.) Methods: We present the analysis of the flaring behavior of the source based on INTEGRAL data and compare it with the flares observed in EXO 2030+375 in 1985. Results: Based on the observational properties of the flares, we argue that the instability at the inner edge of the accretion disk is the most p robable cause of the flaring activity.
 
Key words: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Galaxy Astrophysics

Preprint (261 kb PDF file including figures)
Astrophysics (astro-ph): 1111.3804

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