X-ray And Optical Long Time Scale Light Variation Of Active Galactic Nuclei

Active galaxies are a special class of galaxies,whose core(Active Galactic Nuclei,AGNs)undergoes violent physical processes,which makes its abundant observational phenomena.Variability is one of the typical ones.Luminosity variability refers to the change of AGN radiation flux over time.It has been observed from the radio wave band to the?energy band.It is one of the effective ways to understand the geometric structure and physical properties of active galactic nuclei.In AGN,the accretion disk surrounding a black hole is believed to produce a thermal spectrum.At energies above 2 ke V,the primary X-ray continuum is dominated by the inverse Compton scattering from the hot corona close to the central super-massive black hole,complemented with a reflection component from the accretion disc illuminated by the primary X-ray continuum.In order to investigate the accretion disk and the coronal structure of AGN,We analyze the long-term scale variability of X-ray and Optical wave of radio-quiet Seyfert 1 AGN,which has less influence of relativistic jet in radiation.Compared with short-term variability,long-term variability may correspond to different radiation mechanisms and radiation scales,while has been less studied,thus the investigation of long-term variability could contribute to the understanding of the physical structure of AGN.Using the RXTE(Rossi X-ray Timing Explorer Mission)satellite's 17-year observational data,we select 20 Seyfert 1 galaxies which have at least100 measurements,and analyze their energy spectrum in the X-ray band.To overcome the limitation of the signal resolution,a total of 18,335 energy spectra of the 20 Seyfert1 galaxies are uniformly fitted using a power-rate model,and a single Gaussian function is added when necessary.The overall samples have X-ray Eddington ratio range over 4orders of magnitude.The photon index of each source increases with the luminosity at the hard X-ray(2-10 ke V)band,but different sources show different slopes.Beyond that,we find that there is an anti-correlation between the slope and the X-ray Eddington ratio,which means as the X-ray Eddington ratio increases,the increase of X-ray photon index becomes smaller.This secondary effect of the evolution of energy spectrums demonstrates that it is not a linear function between X-ray Eddington ratio and its phonton index.This might be caused by changes in the geometry of the corona and the viscosity of the accretion disk of the AGN under different Eddington ratios.This effect should be taken into account on the modeling of the structure of the accretion disk and the corona in AGN,as well as the interaction between the two.In the optical wavebands,a subset of 8 years of observation of the 20 radio-quiet Seyfert 1 galaxies is analyzed at the ASAS-SN(All-Sky Automated Survey for Su-pernovae)waveband.The corresponding optical variability amplitudes of the discrete optical data are analyzed statistically and fitted multiple times,based on the principle of random walk model.The fitting procedure provides a better estimation of uncertainty.Through the correlation analysis,we find that in the range of redshift z<0.1,thermal luminosity L₅₁₀₀=10⁴¹-10⁴⁵erg/s,the optical variability has a certain positive corre-lation with the thermal luminosity,and also shows a strong positive correlation with the mass of the black hole,but the correlation with the Eddington ratio is not obvious.Our observation may limit the physics of the nearby low luminosity radio quiet galaxies on the optical long-term radiation.