In this paper we report the discovery of a hard Xray selected Type 2 Seyfert galaxy and we present and discuss its X-ray and optical spectrum together with the radio to X-ray energy distribution. The X-ray source - AXJ2254+1146 - is part of the ASCA Hard Serendipitous Survey (HSS). What makes this discovery particularly noteworthy is the fact that the Spe 2 classification of this Seyfert galaxy has resulted directly from the X-ray data and has been confirmed by optical spectroscopy only subsequently. The X-ray spectrum of AXJ2254+1146 is best described by a model consisting of an unresolved Gaussian line at 6.43 +/- 0.1 keV plus the so called "leaky-absorber" continua having an intrinsic power law photon index of Gamma = 2.51(2.17)(2.76) (1 sigma confidence interval). The best fit values of the absorbing column density (N-H = 1.85(1.47)(2.24) x 10(23) cm(-2)), of the line equivalent width (0.6(0.36)(0.84) keV) and of the scattering fraction (0.7(0.1)(1.4)%), lead us to classify it as a Type 2 AGN from an X-ray point of view. Inspection of the POSS II image reveals the presence, within the ASCA X-ray error circle, of the nearby Sbc spiral galaxy UGC 12237 (m(Bo) = 14.26) that, even on positional ground considerations alone, is the most likely optical counterpart of AXJ2254+1146. Subsequent optical spectroscopy of UGC 12237 has confirmed its Seyfert 2 optical nature.
A hard medium survey with ASCA III. a Type 2 AGN revealed from X-ray spectroscopy
ROSATI, Piero;
2000
Abstract
In this paper we report the discovery of a hard Xray selected Type 2 Seyfert galaxy and we present and discuss its X-ray and optical spectrum together with the radio to X-ray energy distribution. The X-ray source - AXJ2254+1146 - is part of the ASCA Hard Serendipitous Survey (HSS). What makes this discovery particularly noteworthy is the fact that the Spe 2 classification of this Seyfert galaxy has resulted directly from the X-ray data and has been confirmed by optical spectroscopy only subsequently. The X-ray spectrum of AXJ2254+1146 is best described by a model consisting of an unresolved Gaussian line at 6.43 +/- 0.1 keV plus the so called "leaky-absorber" continua having an intrinsic power law photon index of Gamma = 2.51(2.17)(2.76) (1 sigma confidence interval). The best fit values of the absorbing column density (N-H = 1.85(1.47)(2.24) x 10(23) cm(-2)), of the line equivalent width (0.6(0.36)(0.84) keV) and of the scattering fraction (0.7(0.1)(1.4)%), lead us to classify it as a Type 2 AGN from an X-ray point of view. Inspection of the POSS II image reveals the presence, within the ASCA X-ray error circle, of the nearby Sbc spiral galaxy UGC 12237 (m(Bo) = 14.26) that, even on positional ground considerations alone, is the most likely optical counterpart of AXJ2254+1146. Subsequent optical spectroscopy of UGC 12237 has confirmed its Seyfert 2 optical nature.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
