Detecting Compton Reflection and a Broad Iron Line in MCG-5-23-16 with the Rossi X-ray Timing Explorer

Abstract

We report the detection with the Rossi X-ray Timing Explorer of a Compton reflection signature in the Seyfert galaxy MCG-5-23-16. RXTE also resolves the Fe K-alpha fluorescence line with FWHM ~48,000 km s^{-1}. This measurement provides the first independent confirmation of ASCA detections in Seyfert galaxies of broad Fe K-alpha lines that are thought to be the signature of emission from the inner regions of an accretion disk orbiting a black hole. Under the assumption that reflection arises from an isotropic source located above a neutral accretion disk, and using a theoretical model that accounts for the dependence of the reflected spectrum on inclination angle, we derive a 90% confidence range for the disk inclination of i = 50 to 81 degrees. The large inclination is consistent with that expected from the unified model for MCG-5-23-16 based on its Seyfert 1.9 classification. If we assume that the high-energy cutoff in the incident spectrum lies at energies larger than a few hundred keV, then the equivalent width of the Fe K-alpha line is much larger than predicted for the amount of reflection. This implies either an enhanced iron abundance, a covering factor of reflecting material > 0.5, or a cutoff in the incident spectrum at energies between ~60 and ~200 keV.Comment: Accepted for publication in ApJ, LaTeX. 14 pages including 3 figures, with 1 table as a separate postscript file. Typo corrected in abstrac