CAIXA: a catalogue of AGN in theXMM-Newtonarchive

Abstract

Context. We report on the results of the first XMM-Newton systematic "excess variance" study of all the radio quiet, X-ray un-obscured AGN. The entire sample consist of 161 sources observed by XMM-Newton for more than 10 ks in pointed observations, which is the largest sample used so far to study AGN X-ray variability on time scales less than a day. Aims. Recently it has been suggested that the same engine might be at work in the core of every black hole (BH) accreting object. In this hypothesis, the same variability should be observed in all AGN, once rescaled by the M BH (M BH ) and accretion rate (ṁ). Methods. We systematically compute the excess variance for all AGN, on different time-scales (10, 20, 40 and 80 ks) and in different energy bands (0.3-0.7, 0.7-2 and 2-10 keV). Results. We observe a highly significant and tight (∼0.7 dex) correlation between σ 2 rms and M BH . The subsample of reverberation mapped AGN shows an even smaller scatter (only a factor of 2-3) comparable to the one induced by the M BH uncertainties. This implies that X-ray variability can be used as an accurate tool to measure M BH and this method is more accurate than the ones based on single epoch optical spectra. This allows us to measure M BH for 65 AGN and estimate lower limits for the remaining 96 AGN. On the other hand, the σ 2 rms vs. accretion rate dependence is weaker than expected based on the PSD break frequency scaling. This strongly suggests that both the PSD high frequency break and the normalisation depend on accretion rate in such a way that they almost completely counterbalance each other (PSD amp ∝ṁ −0.8 ). A highly significant correlation between σ 2 rms and 2-10 keV spectral index is observed. The highly significant correlations between σ 2 rms and both the L Bol and the FWHM Hβ are consistent with being just by-products of the σ 2 rms vs. M BH relation. The soft and medium σ 2 rms is very well correlated with the hard σ 2 rms , with no deviations from a linear one to one correlation. This suggests that the additional soft components (i.e. soft excess, warm absorber) add a minor contribution to the total variability. Once the variability is rescaled for M BH andṁ, no significant difference between narrow-line and broad-line Seyfert 1 is observed. Conclusions. The results are in agreement with a picture where, to first approximation, all local AGN have the same variability properties once rescaled for M BH andṁ.

The evolution of the disc variability along the hard state of the black hole transient GX 339-4

“…Previous studies have pointed out that the high-frequency PSD does not show a clear scaling with the luminosity/mass-accretion rate both in BHXRBs (Gierliński et al 2008) and AGN (O'Neil et al 2005;Zhou et al 2010;Ponti et al 2012). We observe that the high-frequency fractional rms of GX 339-4 is constant in the hard and very hard band (dominated by the hard X-ray Comptonization continuum) at any luminosity probed.…”

“…Indeed the high-frequency fractional rms (or equivalently the 'excess variance', e.g. Nikołajuk et al 2004;Ponti et al 2012), while being independent of the mass-accretion rate, scales inversely with the BH mass, with a very small scatter (which mostly depends on the uncertainty on M BH ), of the order of less than 0.2-0.4 dex (e.g. O'Neill et al 2005;Zhou et al 2010;Ponti et al 2012;Kelly et al 2011).…”

Anatomy of the AGN in NGC 5548

“…The origin of this variability, which can be even large and fast (e.g., Matt et al 2003), is not fully understood yet (see e.g. McHardy et al 2006;Turner et al 2009;Ponti et al 2012). Variable absorption of the X-ray radiation along the line of sight is one of the possible explanations.…”

A well-monitored, X-ray selected, tidal disruption event

“…3). This rather slow variability implies a relatively high black hole mass and following the prescription of [7] we calculate M BH = 2.5 × 10 7 M from the excess variance with a systematic error of 0.4 dex. It should be pointed out that the correlation of excess variance with M BH in [7] has been calculated using persistent AGN and the disk conditions, leading to the X-ray variability, are not necessarily the same in TDE.…”

“…This rather slow variability implies a relatively high black hole mass and following the prescription of [7] we calculate M BH = 2.5 × 10 7 M from the excess variance with a systematic error of 0.4 dex. It should be pointed out that the correlation of excess variance with M BH in [7] has been calculated using persistent AGN and the disk conditions, leading to the X-ray variability, are not necessarily the same in TDE. From the relationship of black hole mass to bulge K-band luminosity ( [6]) and using a bulge to total-light luminosity ratio for SDSS J1201+30 of 85% ( [13]), we find M BH = 1.8 × 10 7 M , in good agreement with the estimate based on variability.…”