| Abstract : | In the standard accretion disc-corona paradigm, the hard X-ray emission in the radio-quiet category of active galactic nuclei (AGN) is believed to be produced in a hot (~ 10^8-9 k) and compact region called the corona, through inverse Compton process, by the interaction of the seed ultra violet photons from the accretion disc. The shape of the X-ray continuum, among other factors, depends on the temperature of the corona (kTe). Investigating the variation of kTe in AGN and examining the correlation of kTe with other physical parameters such as the photon index, reflection fraction and optical depth could provide important clues to the yet unclear coronal physics in AGN. In this work, we aimed to investigate the variation of kTe in about a dozen AGN that includes NGC 3227, MR 2251-178 and NGC 5548. We carried out spectral analysis of multiple epochs of data acquired using the Nuclear Spectroscopic Telescope Array on our sample of sources. By fitting Comptonization model to the data, we investigated the changes in kTe if any in these sources. We found evidence for variation in kTe in NGC 3227. We also examined the correlations of kTe with other best fit parameters for this source. In MR 2251-178 and NGC 5548 no conclusive evidence for the variation in kTe is found. Details of the results will be presented in the meeting. |
