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Upcoming Seminar/Colloqium


Multi-Wavelength Study of Narrow-Line Seyfert 1 Galaxies

Speaker : Vineet Ojha
Affiliation : ARIES
Date & Time :
Venue : Auditorium
Abstract :

Narrow-line Seyfert 1 galaxies (NLSy1s) are a peculiar class of lower luminosity AGNs, characterized by the narrow width of optical Balmer emission lines FWHM(Hβ)< 2000 km s −1, a small flux ratio [O III ] λ5007 /Hβ < 3 and strong permitted optical/UV Fe ii emission lines. As a class of lower luminous AGN, NLSy1s were initially classified as radio-quiet objects, which were thought not to eject relativistic jets like those observed in radio-loud AGNs. However, a real path break came since the launch of Fermi-Gamma-ray telescope, which has detected 5 NLSy1s in γ-rays, suggest that these lower luminous AGNs can also emit enough radiations in high energies, akin to the blazars. The optical flux variations of AGN occurring on hour-like, or occasionally even shorter time-scales are commonly known as intra-night optical variability (INOV) and it has come to be used quite extensively as a tracer of jet activity in blazars and other classes of AGNs. In the case of blazars, the INOV phenomenon is usually associated with Doppler boosting of the jets radiation, which not only amplifies any emission fluctuations occurring within the jets plasma whose bulk relativistic motion is directed close to our line of sight but also shortens the time-scales. Flux variations on hour-like have already reported in few γ-rays detected NLSy1s, but this study yet not explored for other higher energies detected based sample such as X-rays. Furthermore, the physical mechanisms responsible for higher INOV detections akin to blazars in γ-ray detected NLSy1 galaxies are still debated. Additionally, there are many models proposed to explain the X-ray emissions mechanism for the NLSy1 galaxy, but a perfect model could not be established due to the small available homogeneous sample of X-ray and optical data of NLSy1s. Therefore, a detailed study based on large datasets of X-ray and optical is very important to understand the X-ray emissions mechanism of NLSy1s along with to remove the degeneracy among the possible proposed models, responsible for X-ray emissions in NLSy1s. In my thesis, I mainly focused on the aforementioned interesting problems and found very interesting results. The details of results and conclusions obtained by us for the aforementioned intriguing problems will be explained systematically chapter wise in my talk.

About Speaker :

Mr Vineet Ojha is pursuing PhD thesis work under supervision of Dr Hum Chand. This is his PhD thesis pre-submission talk.