AR-2019-2020

during the 2016 outburst. They found that the QPO and the upper harmonic exhibit shifts in their centroid frequencies in the second observation with respect to the first one. The hardness intensity diagram implies that in contrast to the 2008 and 2014 failed outbursts, the 2016 outburst was a successful one. They also detect the presence of a broad iron K alpha line near 6.5 keV and a reflection hump in the energy range 15-30 keV. Along with the shape of the power density spectra, the nature of the characteristic frequencies and the fractional rms amplitude of the timing features imply that the source stayed in the low/hard state during these observations. Moreover, the photon index and other spectral parameters also indicate the low/hard state behaviour of the source. Unlike the soft lag detected in this source during the 2008 and 2014 failed outbursts, the 2016 outburst showed hard time lags of 0 . 40 ± 0 . 15 s and 0 . 32 ± 0 . 07s in the 0.07-0.4 Hz frequency range. The high Comptonized fraction and the weak thermal component indicate that the QPO is being modulated by the Comptonization process. Strong Xray excess in gamma-ray blazar OJ 287 Main Pal, Pankaj Kushwaha, Gulab C. Dewangan and Pramod Pawar reported a strong soft X-ray excess in the gamma-ray blazar OJ 287 during long exposure in 2015 May, among two of the latest XMM-Newton observations performed in 2015 and 2018 May. In the case of the 2015 May observation, a log parabola model is found to fit the EPIC-pn data well, while a log parabola plus a power law describes the overall simultaneous optical to X-ray spectra, suggesting the excess as the synchrotron tail. This interpretation, however, is inconsistent with the observed spectral break between near-infrared (NIR) and optical spectra, attributed to a standard disk around a supermassive black hole (SMBH). Based on this, they considered two commonly invoked accretion-disk-based models in active galactic nuclei (AGNs) to explain the soft excess: the cool Comptonization component in the accretion disk and the blurred reflection from the partially ionized accretion disk. They found that both cool Comptonization and blurred reflection models provide an equally good fit to the data, and favour a super-heavy SMBH of mass ∼ 10 10 M . Further investigation of about a month-long simultaneous X-ray and ultraviolet (UV) pointing observations revealed a delayed UV emission with respect to the 1.5 10 keV band, favouring X-ray reprocessing phenomenon as the dominant mechanism. The results suggest that the soft excess is probably caused by strong light bending close to the SMBH. The detected soft excess in the 2015 data and its disappearance in the 2018 data is also consistent with the presence of accretion-disk emission, inferred from the NIR-optical spectral break between 2013 May and 2016 March. Disruption of massive star Rupak Roy has been studying mainly the disruption of massive stars at the end of their life- time, known as Core-collapse Supernovae (CCSNe), disruption of stars through tidal forces of the Supermassive Black Holes (SMBHs) at the centers of the galaxies, known as Tidal Disruption Events (TDEs), and disruption of extremely massive stars, known as Superluminous Supernovae (SLSNe), observational aspects of extremely energetic outflows from AGNs, Radio Galaxies, etc. The CCSNe events produce a compact remnant (neutron star or stellar-mass black Hole) due to the collapse of the stellar-core, and its outer material is ejected in the space. Since in the universe, except Hydrogen, almost all other elements are produced at the centers of the stars, and get ejected through stellar-eruptions or supernovae, and produce second-generation stars, study of the supernovae are extremely important to understand this feedback process. This is also important to study the shock physics of the extreme catastrophes and to know the nature of their progenitors. Recently, astronomers have also discovered stellar-disruptions, which are 10-100 times luminous than canonical CCSNe. These are called Superluminous Supernovae (SLSNe), physics of which is still unknown. TDEs are the disruptions of stars by the supermassive black holes (SMBHs, mass ∼ 10 8 M ) at the centers of the galaxies. These extremely energetic phenomena (liberated energy ∼ 10 50 ergs) exist for several months in the sky and observable mainly in X-ray, UV, and Optical wavebands. These are also efficient probes to study the SMBHs in the inactive galaxies. They study these