The X-ray emission of the high-mass X-ray binary IGR J17200−3116

Abstract

The source IGR J17200-3116 was discovered in the hard X-ray band by INTEGRAL. A periodic X-ray modulation at ~326 s was detected in its Swift light curves by our group (and subsequently confirmed by a Swift campaign). In this paper, we report on the analysis of all the Swift observations, which were collected between 2005 and 2011, and of a ~20 ks XMM-Newton pointing that was carried out in 2013 September. During the years covered by the Swift and XMM-Newton observations, the 1-10 keV fluxes range from ~1.5 to 4E-11 erg/cm^2/s. IGR J17200-3116 displays spectral variability as a function of the pulse phase and its light curves show at least one short (a few hundreds of seconds) dip, during which the flux dropped at 20-30% of the average level. Overall, the timing and spectral characteristics of IGR J17200-3116 point to an accreting neutron star in a high-mass system but, while the pulse-phase spectral variability can be accounted for by assuming a variable local absorbing column density, the origin of the dip is unclear. We discuss different possible explanations for this feature, favouring a transition to an ineffective accretion regime, instead of an enhanced absorption along the line of sight.