The measurement and analysis of flux variations in Seyfert galaxy nuclei

Seyfert galaxies have compact nuclei with luminosities only surpassed by quasars, to which they are believed to be related. The most common interpretation of these objects is that their central power source is a black hole with matter accreting towards it. An understanding of these powerful energy sources would vastly increase our knowledge of high energy physics and cosmology. One unexplained characteristic of Seyfert nuclei is that their luminosities are often variable. Some questions relating to this fact are: What is the nature of the variability? How much obscuration is there from matter in the line of sight? What is the shape of the flux continuum? What is the relationship between the variability and other properties of the galaxy and nucleus? This thesis seeks to answer some of these questions, as they critically affect any model put forward to explain the Seyfert phenomenon. 29 southern Seyfert galaxies were chosen for observation. Flux measurements through five colour filters in the 0.3 to 1 μm range were made regularly in the period September 1986 to October 1989 with a single channel photometer and a CCD camera. These were analysed in conjunction with similar data collected by other investigators. Flux changes of 10% or more were observed in most objects. Fluxes through individual colour filters varied proportionally to each other, indicating that the shape of the continuum at these wavelengths remains constant. The flux distribution derived in this manner is shown to be similar for all objects examined. A procedure potentially superior to existing methods is developed to estimate the extinction of Seyfert nuclei from the flux distribution. Spectroscopic observations in the 0.34-0.72 μm range were made for most objects. From these spectra the gas densities and temperatures, degrees of activity and spectral line intensities and widths were derived. Possible spectral variations were investigated. No definite periodic changes in the light curves could be found. However the possibility of regular variations is not completely excluded. The relative amplitude and rate of flux variations are shown to be independent of the luminosity and other nuclear properties.

Grantor dc:publisher.institution

Department of Astronomy

Year dc:date.issued

1990

Author dc:creator

• Winkler, Hartmut

Advisor dc:contributor.advisor

• Fairall, Anthony Patrick

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/17282

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/17282