Detection of an orbital period in the supergiant high-mass X-ray binary IGR J16465-4507 with Swift-BAT

We analysed the IGR J16465-4507 Burst Alert Telescope (BAT) survey data collected during the first 54 months of the Swift mission. The source is in a crowded field and it is revealed through an ad hoc imaging analysis at a significance level of ~14 standard deviations. The 15-50 keV average flux is . The timing analysis reveals an orbital period of 30.243 +/- 0.035 d. The folded light curve shows the presence of a wide phase interval of minimum intensity, lasting ~20 per cent of the orbital period. This could be explained with a full eclipse of the compact object in an extremely eccentric orbit or with the passage of the compact source through a lower density wind at the orbit apastron. The modest dynamical range observed during the BAT monitoring suggests that IGR J16465-4507 is a wind-fed system, continuously accreting from a rather homogeneous wind, and not a member of the supergiant fast X-ray transient class.