Infrared identification of IGR J09026-4812 as a Seyfert 1 galaxy

Context. IGR J09026-4812 was discovered by INTEGRAL in 2006 as a new hard X-ray source. Thereafter, an observation with Chandra pinpointed a single X-ray source within the ISGRI error circle, showing a hard spectrum, and improving its high-energy localisation to a subarcsecond accuracy. Thus, the X-ray source was associated with the infrared counterpart 2MASS J09023731-4813339 whose JHKS photometry indicated a highly reddened source. The high-energy properties and the counterpart photometry suggested a high-mass X-ray binary with a main sequence companion star located 6.3–8.1 kpc away and with a 0.3–10 keV luminosity of $8_{-1}^{\rm +13}$ $\times$ 1034 erg s-1. Aims. New optical and infrared observations were needed to confirm the counterpart and to reveal the nature of IGR J09026-4812. Methods. We performed optical and near infrared observations on the counterpart 2MASS J09023731-4813339 with the ESO/NTT telescope on March 2007. We carried out photometry and spectroscopy in near infrared wavelengths and photometry in optical wavelengths. Results. The accurate astrometry at both optical and near infrared wavelengths confirmed 2MASS J09023731-4813339 as the counterpart of IGR J09026-4812. However, the near infrared images show that the source is extended, thus excluding the possibility of a Galactic compact source. The source spectrum shows three main emission lines identified as the HeI $\lambda1.0830~\mu\mathrm{m}$ line, and the HI Pa$\,\beta$ and Pa$\,\alpha$ lines, typical of galaxies with an active galactic nucleus. The broadness of these lines reached values as large as 4000 km s-1, suggesting a type 1 Seyfert galaxy. The redshift of the source is z = 0.0391 ± 0.0004. Thus, the near infrared photometry and spectroscopy allowed us to classify IGR J09026-4812 as a type 1 Seyfert galaxy