Astronomy and Astrophysics, volume 472, 905-910 (2007/9-4)
INTEGRAL-ISGRI observations of the Cygnus OB2 region. Searching for hard X-ray point sources in a region containing several non-thermal emitting massive stars.
DE BECKER M., RAUW G., PITTARD J.M., SANA H., STEVENS I.R. and ROMERO G.E.
Abstract (from CDS):
We analyze INTEGRAL-ISGRI data in order to probe the hard X-ray emission (above 20keV) from point sources in the CygOB2 region and to investigate the putative non-thermal high-energy emission from early-type stars (Wolf-Rayet and O-type stars). Among the targets located in the field of view, we focus on the still unidentified EGRET source 3EG2033+4118 that may be related to massive stars known to produce non-thermal emission in the radio domain, and on the wide colliding-wind binary WR140. Using a large set of data obtained with the IBIS-ISGRI imager onboard INTEGRAL, we run the OSA software package in order to find point sources in the fully coded field of view of the instrument. Our data do not allow the detection of a lower-energy counterpart of 3EGJ2033+4118 nor of any other new point sources in the field of view, and we derive upper limits on the high-energy flux for a few targets: 3EGJ2033+4118, TeVJ2032+4130, WR140, WR146 and WR147. The results are discussed in the context of the multiwavelength investigation of these objects. The upper limits derived are valuable constraints for models aimed at understanding the acceleration of particles in non-thermal emitting massive stars, and of the still unidentified very-high gamma-ray source TeVJ2032+4130.