Observational Study Of Three Special Active Galactic Nuclei

In the astrophysical studies,objects with special properties are valuable because their nature may be better understood.In recent decades,researches of active galactic nuclei(AGN)and their central engine supermassive black hole(SMBH)are well devel-oped,and some questions are still remained.In this thesis,we will study three AGNs with special properties and discuss the physics on thermal emission of accretion disk for SMBH,recoiling SMBH and absorbing media in AGN environment.We firstly discuss the thermal emission of accretion disk for SMBH.The standard accretion disk model predicted the thermal emission of accretion disks,which have been examined among the X-ray spectra of stellar black hole binaries.However for AGNs with SMBH,the X-ray spectra come mostly from the hot corona above the accretion disk,and there is little observational evidence of the thermal emission of the accre-tion disk.Model suggests that the thermal emission may be easier to be seen among intermediate-mass black holes.RX J1301.9+2747 is a Seyfert galaxy.It may host an intermediate-mass black hole whose mass is estimated to be 8 x 105M(?)according to the optical spectrum.The X-ray spectrum is super soft with spectral index as high as 7,far higher than typical values of?2.We found that the X-ray spectrum can be described by a model which is mainly contributed by a black body emission component.The black body temperature is 30-40 eV,close to the predicted value of standard accretion disk model.On the other hand,the X-ray light curve of RX J1301.9+2747 shows a flare state with flux increased by a factor of 5-7.The transition from quiescent state to flare state occurs in 1-2 ks.During the flare state the X-ray emission becomes harder.The flare state is seen in both of the X-ray observations separated by 9 years.The variability property of J1301.9+2747 is rare among AGNs and the its nature is still not clear.We secondly discuss searching for recoiling SMBHs.The merging of two galaxies will produce a binary SMBH at the center of the newly formed galaxy.Numerical rela-tivity simulations predict that the SMBH can be kicked out of the galaxy in binary black hole mergers with velocities up to several thousand km s-1.We found a candidate re-coiling SMBH in SBS 1421+511 whose Balmer broad emission lines have blue-skewed profiles.The profile of broad emission line can be modeled as emissions from a circular disk with a blueshift velocity of 1450 km s-1 relative to the narrow emission lines.The blueshift velocity is better interpreted as resulting from a recoiling SMBH than from a SMBH binary,since the line profile almost kept steady over one decade in the quasar rest-frame.Alternative interpretations are possible as well,such as emissions from a bipolar outflow or a circular disk with spiral emissivity perturbations.We thirdly discuss quasar absorption lines.LBQS 1206+1052 is a quasar with two sets of absorption lines with blueshift velocities relative to the quasar rest frame of?700 and?1400 km s-1,respectively.Both the two sets have Mg II and He I*absorption,and the first set show rare Balmer absorption lines which trace high den,sity gas.Our spectral monitoring of the quasar show variability in strength of absorption lines for both the two sets.We reproduce all of the spectral data by assuming that only the ionization state of the absorbing gas is variable and that all other physical properties are invariable.The variation of ionization is consistent with the variation of optical continuum from the V-band light curve.Additionally,we cannot interpret the data by assuming that the variability is due to a movement of the absorbing gas.Therefore,our analysis strongly indicates that the absorption-line variability in LBQS 1206+1052 is photoionization driven.As shown from photoionization simulations,the absorbing gas of the first set has a density in the range of 109 to 1010 cm-3 and a distance of?1 pc.We proposed follow-up works in two aspects.One is spectral monitoring of He I*absorption sample to make clear which of the two origins of absorption line variability is more common.The other is spectral monitoring of an AGN sample with Balmer absorption lines to constrain the positions and properties of the absorbers,and further study the distribution of high density gas in AGN enviroment.