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Upcoming Seminar/Colloqium


OJ287: The New Broadband Component and the issue of X-ray spectral changes

Speaker : Pankaj Kushwaha
Affiliation : ARIES
Date & Time :
Venue : Zoom
Abstract :

OJ 287 is a BL Lacertae (BL Lac) object and is one of the best candidate binary supermassive black hole systems. It is well-known for strong and rapid flux variability -- typical of blazars. However, unlike most of the blazars, often the flux variability is accompanied by strong spectral changes, particularly at X-rays that have been argued to be a new emission component. It underwent its brightest reported X-ray activity in 2017 and the 2nd brightest in 2020. In this talk, I will present results from detailed and systematic multi-wavelength studies of these activity phases and show that the two brightest phases with an extremely soft X-ray spectrum are due to a new broadband jet emission component of the HBL type but with some peculiar timing features. Using constraints offered by this new component and the Far-UV observations of AstroSat, we further show that the intermediate X-ray spectra are due to the extension of the synchrotron component to X-ray energies, contrary to the previous arguments attributing it to a new emission component. Finally, I will briefly discuss the implications of these results on a few of the jet physics issues.

About Speaker :

Dr. Pankaj Kushwaha is a DST-INSPIRE faculty fellow at ARIES.