Multi-wavelength properties of the high-energy bright Seyfert 1 galaxy IGR J18027-1455

¹ Departamento de Física (EPS), Universidad de Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain e-mail: jcombi@ujaen.es
² Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
³ AIM – Astrophysique Interactions Multi-échelles (UMR 7158 CEA/CNRS/Université Paris 7 Denis Diderot), CEA Saclay, DSM/DAPNIA/Service d'Astrophysique, Bât. 709, L'Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France

Received: 7 April 2006
Accepted: 8 August 2006

Abstract

A new sample of hard X-ray sources in the Galactic Plane is being revealed by the regular observations performed by the INTEGRAL satellite. The full characterization of these sources is mandatory to understand the hard X-ray sky. Here we report new multifrequency radio, infrared and optical observations of the source IGR J18027-1455, as well as a multi-wavelength study from radio to hard X-rays. The radio counterpart of IGR J18027-1455 is not resolved at any observing frequency. The radio flux density is well fitted by a simple power law with a spectral index . This value is typical of optically thin non-thermal synchrotron emission originated in a jet. The NIR and optical spectra show redshifted emission lines with , and a broad Hα line profile with km s^-1. This suggests an Active Galactic Nucleus (AGN) of type 1 as the optical counterpart of IGR J18027-1455. We confirm the Seyfert 1 nature of the source, which is intrinsically bright at high energies both in absolute terms and when scaled to a normalized 6 cm luminosity. Finally, comparing its X-ray luminosity with isotropic indicators, we find that the source is Compton thin and AGN dominated. This indicates that INTEGRAL might have just seen the tip of the iceberg, and several tens of such sources should be unveiled during the course of its lifetime.