Pre-submission Thesis Presentation

Although, extensive observations and theoretical studies have been carried out on the BL Lacs, there are several aspects of these objects that remain poorly understood e.g. mechanisms responsible for particle acceleration in the jets, the structure of the magnetic fields within the jets, and the underlying causes of the observed variability in jet emission. My thesis work is focused on the study of two BL Lac sources: PKS 0903-57 & Markarian (Mrk) 180, which remained less explored until recently. For PKS 0903-57, 12-year-long Fermi-LAT data have been analysed for the first time for detailed temporal and spectral study. We identified ‘flaring’ events and calculated variability time, flare rising, and decaying time to investigate the emission process. Subsequent investigations included modeling the multi-wavelength spectral energy distribution (MWSED) with one-zone pure leptonic emission during the identified flaring phases to know the nature of this source. The other source, Mrk 180, is a potential candidate for high-energy cosmic-ray acceleration. With detailed temporal, spectral studies and MWSED modeling, we found that one-zone pure leptonic model is insufficient for explaining its long-term MWSED, and we explained it with a lepto-hadronic scenario. Moreover, according to an earlier study, Mrk 180 is associated with the Telescope Array (TA) ultrahigh energy hotspot events having energy more than 57 EeV, we examined whether Mrk 180 could be a source of ultrahigh energy cosmic rays with our simulation results. I will discuss the results of our studies on these sources.