The 1-50 keV spectral and timing analysis of IGR J18027-2016: an eclipsing, high mass X-ray binary
Hill, A. B.; Knigge, C.; Walter, R.; Bird, A. J.; Ubertini, P.; Malizia, A.; Bazzano, A.; Dean, A. J.; Bélanger, G.; Galache, J. L.; Renaud, M.; Stephen, J.
United Kingdom, Switzerland, Italy, France
Abstract
We report the association of the INTEGRAL source IGR J18027-2016 with the BeppoSAX source SAX J1802.7-2017. IGR J18027-2016 is seen to be a weak, persistent source by the IBIS/ISGRI instrument on board INTEGRAL with an average source count rate of 0.58 counts s-1 ( 6.4 mCrab) in the 20-40 keV band. Timing analysis performed on the ISGRI data identifies an orbital period of of 4.5696 ± 0.0009 days and gives an ephemeris of mid-eclipse as, T_mid = 52 931.37 ± 0.04 MJD. Re-analysis of archival BeppoSAX data has provided a mass function for the donor star, f(m) = 16 ± 1 M⊙ and a projected semimajor axis of axsin{i} = 68 ± 1 lt-s. We conclude that the donor is an OB-supergiant with a mass of 18.8-29.3 M⊙ and a radius of 15.0-23.4 R⊙. Spectra obtained by XMM-Newton and ISGRI indicate a high hydrogen column density of NH = 6.8 × 1022 cm-2, which suggests intrinsic absorption. The source appears to be a high mass X-ray binary with the neutron star emitting X-rays through wind-fed accretion while in an eclipsing orbit around an OB-supergiant.