""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 ((m) over dot). 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 (similar to 0.7 dex) correlation between sigma(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 sigma(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 (PSDamp proportional to (m) over dot(-0.8)). A highly significant correlation between sigma(2)(rms) and 2-10 keV spectral index is observed. The highly significant correlations between sigma(2)(rms) and both the L-Bol and the FWHMH beta are consistent with being just by-products of the sigma(2)(rms) vs. M-BH relation. The soft and medium sigma(2)(rms) is very well correlated with the hard sigma(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 and (m) over dot, 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 and (m) over dot. RI Bianchi, Stefano\\\/B-4804-2010 OI Bianchi, Stefano\\\/0000-0002-4622-4240""
Ponti, G., Papadakis, I., Bianchi, S., Guainazzi, M., Matt, G., Uttley, P., et al. (2012). CAIXA: a catalogue of AGN in the XMM-Newton archive III. Excess variance analysis. ASTRONOMY & ASTROPHYSICS, 542 [10.1051/0004-6361/201118326].
CAIXA: a catalogue of AGN in the XMM-Newton archive III. Excess variance analysis
BIANCHI, STEFANO;MATT, Giorgio;
2012-01-01
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 ((m) over dot). 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 (similar to 0.7 dex) correlation between sigma(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 sigma(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 (PSDamp proportional to (m) over dot(-0.8)). A highly significant correlation between sigma(2)(rms) and 2-10 keV spectral index is observed. The highly significant correlations between sigma(2)(rms) and both the L-Bol and the FWHMH beta are consistent with being just by-products of the sigma(2)(rms) vs. M-BH relation. The soft and medium sigma(2)(rms) is very well correlated with the hard sigma(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 and (m) over dot, 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 and (m) over dot. RI Bianchi, Stefano\\\/B-4804-2010 OI Bianchi, Stefano\\\/0000-0002-4622-4240""I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
