Chandra Localizations and Spectra of Integral Sources in the Galactic Plane

We report on the results of observations of hard X-ray sources in the Galactic plane with the Chandra X-ray Observatory. The hard X-ray “IGR” sources were discovered by the INTEGRAL satellite, and the goals of the Chandra observations are to provide sub-arcsecond localizations to obtain optical and infrared counterparts and to provide constraints on their 0.3–10 keV spectra. We obtained relatively short, ∼5 ks, observations for 20 IGR sources and find a bright Chandra source in INTEGRAL error circles in 12 cases. In 11 of these cases, a crosscorrelation with optical and/or infrared source catalogs yields a counterpart, and the range of J-band magnitudes is 8.1–16.4. Also, in 4 cases, the Chandra X-ray spectra show evidence for absorbing material surrounding the compact object with a column density of local material in excess of 5 × 1022 cm−2. We confirm that IGR J00234+6141 is a Cataclysmic Variable and IGR J14515–5542 is an Active Galactic Nucleus (AGN). We also confirm that IGR J06074+2205, IGR J10101–5645, IGR J11305–6256, and IGR J17200–3116 are High Mass X-ray Binaries (HMXBs). Our results (along with follow-up optical spectroscopy reported elsewhere) indicate that IGR J11435–6109 is an HMXB and IGR J18259–0706 is an AGN. We find that IGR J09026– 4812, IGR J18214–1318, and IGR J18325–0756 may be HMXBs. In cases where we do not find a Chandra counterpart, the flux upper limits place interesting constraints on the luminosities of black hole and neutron star X-ray transients in quiescence. Subject headings: stars: neutron — stars: white dwarfs — black hole physics — X-rays: stars — infrared: stars — stars: individual (IGR J00234+6141, IGR J01363+6610, IGR J06074+2205, IGR J09026–4812, IGR J10101–5645, IGR J11305–6256, IGR J11435–6109, IGR J14515– 5542, IGR J17200–3116, IGR J17285–2922, IGR J17331–2406, IGR J17407–2808, IGR J17445–2747, IGR J17507–2856, IGR J18193–2542, IGR J18214–1318, IGR J18256– 1035, IGR J18259–0706, IGR J18325–0756, IGR J18539+0727)