INTEGRAL observations of OAO 1657-415: gamma-ray tomography of a B   supergiant
  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 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 supergiant companion. We find that the density profile of the outer layer can be described by a power law with the index   $\alpha = 8.5$. We also note that the fit hints toward smaller inclinations of the system within the allowed range 60-90 degrees. 
M. Denis, T. Bulik, R. Marcinkowski