NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-18 T02:24:24 PDT
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For refcode 2001MNRAS.324..653L:
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NED Abstract

Copyright by Royal Astronomical Society. 2001MNRAS.324..653L The relationship between X-ray variability and the central black hole mass Youjun Lu, and Qingjuan Yu Accepted 2001 January 12. Received 2000 December 12; in original form 2000 April 18 ABSTRACT We assembled a sample of Seyfert 1 galaxies, quasi-stellar objects (QSOs) and low-luminosity active galactic nuclei (LLAGNs) observed by ASCA, the central black hole masses of which have been measured. We found that the X- ray variability (which is quantified by the 'excess variance' {sigma}_rms_^2^) is significantly anti-correlated with the central black hole mass, and it is likely that a linear relationship of {sigma}_rms_^2^ is proportional to M_bh_^-1^ exists. It can be interpreted that the short time-scale X-ray variability is caused by some global coherent variations in the X-ray emission region, which is scaled by the size of the central black hole. Hence the central black hole mass is the driving parameter of the previously established relation between X-ray variability and luminosity. Our findings favour the hypothesis that the narrow-line Seyfert 1 galaxies and QSOs harbour smaller black holes than the broad-line objects, and can also easily explain the observational fact that high- redshift QSOs have greater variability than local AGNs at a given luminosity. Further investigations are needed to confirm our findings, and a large sample X-ray variability investigation can give constraints on the physical mechanisms and evolution of AGNs. Keywords: galaxies: active - galaxies: nuclei - galaxies: Seyfert - X-rays: galaxies
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