The broad-band spectrum of Cyg X-2 with INTEGRAL (Research Note)

Abstract

We study the broad band (3-100 keV) spectrum of Cygnus X-2 with INTEGRAL. We find that the spectrum is well fitted by a Comptonized component with a seed-photons temperature of ∼1 keV, an electron temperature of ∼3 keV and an optical depth τ ∼ 8. Assuming spherical geometry, the radius of the seed-photons emitting region is ∼17 km. The source shows no hard X-ray emission; it was detected only at a 3σ level above 40 keV. We also analyzed public ISGRI data of Cyg X-2 to investigate the presence of a hard X-ray component. We report the possible presence of hard X-ray emission in one data set. © ESO 2006.