INTEGRAL Observations of OAO 1657-415: Gamma-Ray Tomography of a B Super Giant

Abstract

OAO 1657-415 is an accreting pulsar in an eclipsing binary system. We analyzed the INTEGRAL core program observations of this object and obtained the eclipse light curve in the soft gamma-ray band between 15 keV and 40 keV. We note that the gamma rays from the pulsar allow to probe the density profile of the outer layers of the B super giant companion. We find that the density profile of the outer layer can be described by a power law with the index α=8.5. We also note that the fit hints toward smaller inclinations of the system within the allowed range 60°<i<90°.