The long time-scale X-ray variability of the radio-quiet quasar PG 0804+761

Abstract

We present the results from a study of the timing properties and the energy spectrum of the radio-quiet quasar PG0804+761, based on monitoring RXTE PCA observations that lasted for a year. This is a systematic study of the X-ray variations on time scales of weeks/months of the most luminous radio-quiet quasar studied so far. We detect significant variations in the 2-10 keV band of an average amplitude of ~15%. The excess variance of the light curve is smaller than that of Seyfert galaxies, entirely consistent with the relationship between variability amplitude and luminosity defined from the Seyfert data alone. The power spectrum of the source follows a power-like form of slope ~ -1. However, when we extend the power spectrum estimation at higher frequencies using archival ASCA data, we find strong evidence for an intrinsic steepening to a slope of ~ -2 at around ~ 1x10^(-6) Hz. This "break frequency" corresponds to a time scale of ~ 10 days. The time-average energy spectrum is well fitted by a power law model with Gamma ~ 2. We also find evidence for an iron line at \~ 6.4 keV (rest frame) with EW 110 eV, similar to what is observed in Seyfert galaxies. The flux variations are not associated with any spectral variation. This is the only major difference that we find when we compare the variability properties of the source with those of Seyfert galaxies. Our results support the hypothesis that the same X-ray emission and variability mechanism operates in both Seyfert galaxies and quasars.

8 pages, 6 figures, accepted for publication in MNRAS

References in corpus (3)

• X-ray continuum variability of MCG-6-30-15
• The nature of X-ray spectral variability in Seyfert Galaxies
• Black Hole Masses in Three Seyfert Galaxies

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• The scaling of the X-ray variability with black hole mass in AGN
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• The dust-gas AGN torus as constrained from X-ray and mid-infrared observations
• The X-ray Power Spectral Density Function and Black Hole Mass Estimate for the Seyfert AGN IC 4329a
• A correlation between the spectral and timing properties of AGN
• XMM-Newton long-look observation of the narrow line Seyfert 1 galaxy PKS0558-504; I: Spectral analysis
• Long-Term X-Ray spectral variability of the radio-loud NLS1 galaxy PKS 0558-504
• Extended Corona Models of X-ray Reverberation in the AGN 1H~0707-495 and IRAS 13224-3809