Observation of Cen A by the Rossi X-ray Timing Explorer

R. E. Rothschild, D. L. Band, P. R. Blanco, D. E. Gruber, W. A. Heindl, D. R. MacDonald, D. C. Marsden, K. Jahoda, D. Pierce, G. Madejski, M. Elvis, D. A. Schwartz, R. Remillard, A. A. Zdziarski, C. Done, R. Svensson

Published 1998-08-05Version 1

The Rossi X-ray Timing Explorer made a short (10 ks) observation of the radio galaxy Centaurus A on 14 August 1996. Analysis of the combined 2.5-240 keV spectrum has revealed a heavily absorbed(NH=9.42+/-0.24 e22 cm-2) primary power law (index=1.86+/-0.015) and an iron line due to fluorescence of cold matter (EW=162+/-25 eV). Flux from either a jet, primary flux scattered into the line of sight, or primary flux seen through a partial absorber was not required. The iron line width is unresolved at the 95% confidence level (sigma < 0.54 keV). No significant variability in the iron line flux is seen from measurements over the last two decades, while the overall continuum flux varied by more than a factor of four, which implies that the line emission region is distant from that of the primary emission. While radio-quiet Seyfert galaxies exhibit spectral components attributable to Compton reflection from cold matter, Cen A reveals no such component (exposed solid angle ratio < 0.09). This supports unified models of active galaxies that have little difference between Seyfert 2 and low luminosity radio galaxies