INTEGRAL observations of the Be/X-ray binary EXO 2030+375 during outburst

¹ GACE, Instituto de Ciencias de los Materiales, Universidad de Valencia, PO Box 20085, 46071 Valencia, Spain e-mail: Ascension.Camero@uv.es
² XD12 NASA Marshall Space Flight Center, Huntsville, AL 35812, USA
³ NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA
⁴ Joint Center for Astrophysics, Depart. of Physics, University of Maryland, Baltimore County, MD 21250, USA

Received: 28 April 2005
Accepted: 5 June 2005

Abstract

We present a type–I outburst of the high-mass X-ray binary EXO 2030+375, detected during INTEGRAL's Performance and Verification phase in December 2002 (on-source time about 10⁶ s). In addition, six more outbursts have been observed during INTEGRAL's Galactic Plane Scans. X-ray pulsations have been detected with a pulse period of  s. The X-ray luminosity in the 5-300 keV energy range was  erg s^-1, for a distance of 7.1 kpc. Two unusual features were found in the light curve, with an initial peak before the main outburst and another possible spike after the maximum. RXTE observations confirm only the existence of the initial spike. Although the initial peak appears to be a recurrent feature, the physical mechanisms producing it and the possible second spike are unknown. Moreover, a four-day delay between periastron passage and the peak of the outburst is observed. We present for the first time a 5-300 keV broad-band spectrum of this source. It can be modelled by the sum of a disk black body ( keV) with either a power law model with  keV or a Comptonized component (spherical geometry,  keV, ,  keV).