Rosat, Asca and Osse Observations of the Broad Line Radio Galaxy 3C120

Abstract

We present simultaneous observations of the superluminal radio galaxy 3C120 performed with the ASCA and GRO (OSSE) satellites on February-March 1994, as well as an analysis of all the ROSAT archival data. The ASCA spectrum of this object can be described by an absorbed (N_H=1.6e^21 cm^-2) power law with photon index Gamma_ASCA=2 and a very broad sigma>0.8 keV intense iron line (EW>400 eV) at ~ 6 keV. The combined ASCA--OSSE data do not exclude the presence of a narrower (sigma=0.4 keV) and less intense (EW<300 eV) iron line plus a hard component, corresponding either to reflection from an accretion disk or to a flatter power law from a jet. However a single power law plus broad Fe line is preferred from a statistical point of view by the ASCA data. The ROSAT data yield a column density in excess of the Galactic value. The spectral slopes, ranging from Gamma_ROSAT=2.5 to 3.3, are steeper than that measured by ASCA, suggesting the presence of a soft excess. The 0.1-2 keV power-law slope is variable and softer at higher intensity. These results show that the combined soft and hard X-ray spectrum of 3C120 is rather complex. The intrinsic absorption, the soft excess, and the iron line indicate that the X-ray emission from this blazar-like radio galaxy is dominated by a Seyfert-like component, at least in the 0.1-10keV energy band. The jet contribution, if present, becomes important only at higher energies.