NGC 3147: a `true' type 2 Seyfert galaxy without the broad-line region
Bianchi, S.; Jiménez-Bailón, E.; Barcons, X.; Bassani, L.; Carrera, F. J.; Matt, G.; Panessa, F.; Corral, A.
Italy, Spain, Mexico
Abstract
We report on simultaneous optical and X-ray observations of the Seyfert galaxy, NGC 3147. The XMM-Newton spectrum shows that the source is unabsorbed in the X-rays (NH < 5 × 1020 cm-2). On the other hand, no broad lines are present in the optical spectrum. The origin of this optical/X-rays misclassification (with respect to the Unification Model) cannot be attributed to variability, since the observations in the two bands are simultaneous. Moreover, a Compton-thick nature of the object can be rejected on the basis of the low-equivalent width of the iron Kα line (~=130 eV) and the large ratio between the 2-10 keV and the [OIII] fluxes. It seems therefore inescapable to conclude that NGC 3147 intrinsically lacks the Broad-Line Region, making it the first `true' type 2 Seyfert galaxy.