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A&A 399, 1121-1134 (2003)
DOI: 10.1051/0004-6361:20021854

Gamma-ray emission from Wolf-Rayet binaries

P. Benaglia and G. E. Romero

Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Buenos Aires, Argentina
(Received 14 May 2002 / Accepted 4 December 2002)

Abstract
In the colliding wind region of early-type binaries, electrons can be accelerated up to relativistic energies displaying power-law spectra, as demonstrated by the detection of non-thermal radio emission from several WR+OB systems. The particle acceleration region, located between the stars, is exposed to strong photon fields in such a way that inverse Compton cooling of the electrons could result in a substantial high-energy non-thermal flux. In particular cases, the ratio of the energy densities of magnetic to photon fields in the colliding wind region will determine whether a given source can produce or not significant gamma-ray emission. We present here a study of the binaries WR 140, WR 146, and WR 147 in the light of recent radio and gamma-ray observations. We show that with reasonable assumptions for the magnetic field strength WR 140 can produce the gamma-ray flux from the EGRET source 3EG J2022+4317. WR 146 and WR 147 are below the detection threshold, but new and forthcoming instruments like INTEGRAL and GLAST might detect non-thermal emission from them.

Key words: stars: early-type -- stars: binaries: general -- stars: winds, outflows -- radio continuum: stars -- gamma-rays: observations -- gamma-rays: theory

Offprint request: P. Benaglia, paula@lilen.fcaglp.unlp.edu.ar

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