The Study Of Multi-wavelength Variability Of Quasars

Since the 1960s,the quasar was fist discovered which was always one of the hot topic field in astrophysics.Extreme variability is one characteristics of quasars.Therefore,the study on variability of quasars is one means for us to understand the physical mech-anism in quasars.The thesis study the variability of quasar carefully.The three works in variability aspects are listed as follows.First,we mainly study the variability of 144 radio quiet quasars from random se-lection in SDSS.The ensemble result indicates it is consistent with the damped random walk(DRW)model.The individual result suggest ten objects are deviated from the damped random walk model.We further examine the probability deviating from the damped random walk model by simulating light curve,which present 70%probability deviated from the DRW model.Second,we select the data release 7 quasar sample and analyze the mid-infrared variability of quasars.The analysis are presented as follows,(1).There are no obvious variation between the structure function in one year and bolometric luminosity,black hole mass as well as Eddington ratio.(2).The slopes in W1 band and W2 band are steeper than that in previous studies,which may be caused by different sampling.(3).We further investigate the relationship of variability amplitude between optical band and mid-infrared band.No obvious trend is found.We also investigate the color re-lationship between W1-W2 and g-r,which shows no obvious correlation.We think it may be smoothed out by the extended emission region in infrared band.(4).We select a radio-loud subsample to investigate the relationship between variability amplitude and radio power at 1.4 GHz,thus the results suggest they are no obvious correlation.The results indicate the mid-infrared emission originated from relativistic jet is weak.Third,we investigate the optical variability of a large narrow-line Seyfert 1 sample,and the optical data sets are from Pan-STARRS1.The results are listed as follows,(1).We analyze the variability amplitude with the luminosity in g,r,i,z and y bands.The results suggest the amplitude become weaker with brighter,which is consistent with previous results.(2).We analyze the relation between variability amplitude and MBH.L5100A and other parameters,but no previous correlations are found in our results.(3).At last,we analyze the relation between variability amplitude and radio power at 1.4 GHz,but also no obvious correlations are found.The variability in narro-line Seyfert 1 galaxies is weak in optical band,then it is difficult to find the contribution of variation from relativistic jet by statistical method.In order to probe the contribution from relativistic jet,we will mainly focus on a few narrow-line Seyfert 1 galaxies with strong variability in the future.At last,the development in the field of quasar in the future is included in section five.With the LSST,eROSITA,etc will be put into use,we anticipate much more exciting discovery in the field of quasar.