X-Ray Continuum and Iron K Emission Line from the Radio Galaxy 3C 390.3
Elvis, M.; Fabbiano, G.; Hayashida, K.; Barr, P.; Makishima, K.; Tashiro, M.; Trinchieri, G.; Ohashi, T.; Palumbo, G. G. C.; Inda, M.; Kohmura, Y.
Japan, Italy
Abstract
X-ray properties of the radio galaxy 3C 390.3 were investigated using the EXOSAT and Ginga satellites. Long-term, large-amplitude X-ray intensity changes were detected over a period extending from 1984 through 1991, and high-quality X-ray spectra were obtained especially with Ginga. The X-ray continuum spectra were described with power-law model with photon slope in the range 1.5-1.8, and the slope flattened as the 2-20 keV luminosity decreased by 40%. There was a first detection of the iron emission line from this source at the 90% confidence level. An upper limit was derived on the thermal X-ray component. X-ray emission mechanisms and possible origins of the long-term variation are discussed.