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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 (AGN). We employ a wavelet technique to analyze 19 observations of 10 AGN obtained with the [*XMM-Newton*]{} EPIC-PN camera. We report the detection of a candidate 3.3 kilosecond quasi-period in 3C 273. If this period represents an orbital timescale originating near a last stable orbit of 3 $R_S$, it implies a central black hole mass of $7.3\times 10^6$ M$_\sun$. For a maximally rotating black hole with a last stable orbit of 0.6 $R_S$, a central black hole mass of $8.1\times 10^7$ M$_\sun$ 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 $2.35\times 10^8$ M$_\sun$. 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.'
author:
- 'C. Espaillat, J. Bregman, P. Hughes, and E. Lloyd-Davies'
title: 'Wavelet Analysis of AGN X-ray Time Series: A QPO in 3C 273?'
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Introduction
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Quasi-periodic oscillations (QPOs) are thought to originate in the inner accretion disk 