M.Sc Thesis

M.Sc StudentRosner Shahar
SubjectPhotometric and Spectroscopic Study of Active Galactic
Nuclei Variability
DepartmentDepartment of Physics
Supervisor PROF. Ari Laor
Full Thesis textFull thesis text - English Version


In this research thesis, the variability of active galactic nuclei is studied using photometric and spectroscopic methods. For this study, two monitoring campaigns were performed, and their data was analyzed and compared to existing results. The first campaign was photometric monitoring of 21 quasars from the Sloan Digitized Sky Survey (SDSS) sample. The main purpose of this campaign was to correlate the physical and variability parameters of these objects and compare it to existing relations. The objects were monitored over a period of two years, between 2006 and 2008, at the Wise observatory in Mitzpe-Ramon , Israel. The results of this campaign were added to existing data, taken from previous works, on objects in the SDSS sample and additional objects in the Palomar-Green sample. This data also includes physical parameters like redshift, black hole mass and luminosity. Correlations were made between the physical parameters and themselves, and between the physical parameters and the variability parameters. Correlations reported by previous studies have also been noticed during this campaign. Among them, are the very powerful black hole mass - luminosity relation and the somewhat weak black hole mass - magnitude variability gradient. These black hole mass correlations give the relations MBH~LR(1.57) and log(MBH)~-4<grad R>. A new correlation was noticed, which was not noted in previous works, between the luminosity and the magnitude variability gradient. This correlation gives the relation log(LR)~-2.2<grad R>.

The second campaign was spectroscopic study of two quasars, V396HER and SDSS135724, both showing variability in their visible waveband emission. The main purpose of this campaign was to use reverberation mapping in order to estimate the broad line region and the black hole mass of the objects and compare it to the black hole mass - luminosity and broad line region - luminosity relations from previous studies. For both objects, the spectra were taken with the 9.2 meters Hobby-Eberly Telescope, or HET, which is located at McDonald observatory. Reverberation mapping was performed on the continuum and the broad emission lines, resulting in the black hole masses and the broad line region radius of the objects. All the results are elaborated in the 'Results and Discussion' section of the work. The main finding in this campaign was that the black hole mass and broad line region size that were calculated using reverberation mapping did not agree with the values found by using the two luminosity relations. Only one value, the black hole mass of V396HER, seemed to agree between these two methods.