ﻻ يوجد ملخص باللغة العربية
The relation between the 2-10 keV, long term, excess variance and AGN black hole mass is considered in this work. A significant anti-correlation is found between these two quantities in the sense that the excess variance decreases with increasing black hole mass. This anti-correlation is consistent with the hypothesis that the 2-10 keV power spectrum in AGN follows a power law of slope -2 at high frequencies. It then flattens to a slope of -1 below a break frequency until a second break frequency below which it flattens to a slope of zero. The ratio of the two break frequencies is equal to 10-30, similar to the ratio of the respective frequencies in Cyg X-1. The power spectrum amplitude in the frequency x power space does not depend on black hole mass. Instead it is roughly equal to 0.02 in all objects. The high frequency break decreases with increasing black hole mass according to the relation 1.5x(10^-6)/(BHmass/(10^7) solar masses) Hz, in the case of classical Seyfert 1 galaxies. The excess variance of NGC4051, a Narrow Line Seyfert 1 object, is larger than what is expected for its black hole mass and X-ray luminosity. This can be explained if its high frequency break is 20 times larger than the value expected in the case of a classical Seyfert 1 with the same black hole mass. Finally, the excess variance vs X-ray luminosity correlation is a byproduct of the excess variance vs black hole mass correlation, with AGN accreting at ~ 0.1-0.15 the Eddington limit. These results are consistent with recent results from the power spectral analysis of AGN.
We propose a new method of estimation of the black hole masses in AGN based on the normalized excess variance, sigma_{nxs}^2. We derive a relation between sigma_{nxs}^2, the length of the observation, T, the light curve bin size, Delta t, and the bla
We have investigated the relationship between the 2-10 keV X-ray variability amplitude and black hole mass for a sample of 46 radio-quiet active galactic nuclei observed by ASCA. Thirty-three of the objects in our sample exhibited variability over a
A calibration is made for the correlation between the X-ray Variability Amplitude (XVA) and Black Hole (BH) mass. The correlation for 21 reverberation-mapped Active Galactic Nuclei (AGN) appears very tight, with an intrinsic dispersion of 0.20 dex. T
In the past decades, the phenomenology of fast time variations of high-energy flux from black-hole binaries has increased, thanks to the availability of more and more sophisticated space observatories, and a complex picture has emerged. Recently, mod
We present the results from a detailed X-ray variability analysis of 66 AGN in the Lockman Hole, which have optical spectroscopic identifications. We compare, quantitatively, their variability properties with the properties of local AGN, and we study