Wavelet Analysis of AGN X-Ray Time Series: A QPO in 3C 273?

TL;DR

This study uses wavelet analysis on X-ray data from AGNs, notably 3C 273, to detect quasi-periodic signals that inform black hole mass estimates, revealing potential oscillatory modes in accretion disks.

Contribution

It introduces a wavelet-based method to identify QPOs in AGN X-ray data and applies it to 3C 273, providing new insights into black hole mass estimates.

Findings

Detected a 3.3 ks QPO candidate in 3C 273.

Estimated black hole mass ranges from 7.3 million to 81 million solar masses.

Reverberation-mapping results suggest a higher black hole mass, indicating possible higher order disk oscillations.

Abstract

Quasi-periodic signals have yielded important constraints on the masses of black holes in galactic X-ray binaries, and here we extend this to active galactic nuclei (AGNs). We employ a wavelet technique to analyze 19 observations of 10 AGNs obtained with the XMM-Newton EPIC pn camera. We report the detection of a candidate 3.3 ks quasi period in 3C 273. If this period represents an orbital timescale originating near a last stable orbit of 3Rs, it implies a central black hole mass of 7.3x10^6 Msun. For a maximally rotating black hole with a last stable orbit of 0.6Rs, a central black hole mass of 8.1x10^7 Msun is implied. Both of these estimates are substantially lower than previous reverberation-mapping results, which place the central black hole mass of 3C 273 at about 2.35 x10^8 Msun. Assuming that this reverberation mass is correct, the X-ray quasi period would be caused by a higher order oscillatory mode of the accretion disk.