2016MNRAS.456.2717C

IGR J16195-4945 is a hard X-ray source discovered by INTEGRAL during the Core Programme observations performed in 2003. We analysed the X-ray emission of this source exploiting the Swift-Burst Alert Telescope (BAT) survey data from 2004 December to 2015 March, and all the available Swift-X-ray Telescope (XRT)-pointed observations. The source is detected at a high significance level in the 123-month BAT survey data, with an average 15-150 keV flux of the source of ∼ 1.6 mCrab. The timing analysis on the BAT data reveals with a significance higher than six standard deviations the presence of a modulated signal with a period of 3.945 d, that we interpret as the orbital period of the binary system. The folded light curve shows a flat profile with a narrow full eclipse lasting ∼ 3.5 percent of the orbital period. We requested phase-constrained XRT observations to obtain a more detailed characterization of the eclipse in the soft X-ray range. Adopting reasonable guess values for the mass and radius of the companion star, we derive a semimajor orbital axis of ∼ 31R_☉, equivalent to ∼ 1.8 times the radius of the companion star. From these estimates and from the duration of the eclipse, we derive an orbital inclination between 55 and 60 deg. The broad-band time-averaged XRT+BAT spectrum is well modelled with a strongly absorbed flat power law, with absorbing column NH = 7x10²²/cm2 and photon index Γ = 0.5, modified by a high energy exponential cutoff at Ecut = 14 keV.