The X-Ray Power Spectral Density Function and Black Hole Mass Estimate for the Seyfert Active Galactic Nucleus IC 4329a

Abstract

We present the X-ray broadband power spectral density function (PSD) of the X-ray-luminous Seyfert IC 4329a, constructed from light curves obtained via Rossi X-ray Timing Explorer monitoring and an XMM-Newton observation. Modeling the 3-10 keV PSD using a broken power-law PSD shape, a break in power-law slope is significantly detected at a temporal frequency of 2.5^+2.5 _-1.7 × 10^-6 Hz, which corresponds to a PSD break timescale T _b of 4.6^+10.1 _-2.3 days. Using the relation between T _b, black hole mass M _BH, and bolometric luminosity as quantified by McHardy and coworkers, we infer a black hole mass estimate of M _BH = 1.3^+1.0 _-0.3 × 10⁸ M _sun and an accretion rate relative to Eddington of 0.21^+0.06 _-0.10 for this source. Our estimate of M _BH is consistent with other estimates, including that derived by the relation between M _BH and stellar velocity dispersion. We also present PSDs for the 10-20 and 20-40 keV bands; they lack sufficient temporal frequency coverage to reveal a significant break, but are consistent with the same PSD shape and break frequency as in the 3-10 keV band.