Conveners
AGNs & Blazars: Session 1
- Santabrata Das (IIT Guwahati)
AGNs & Blazars: Session 2
- Vaidehi Paliya (IUCAA)
High-energy ($>$100 MeV) emission is one of the defining characteristics of active galactic nuclei (AGN) hosting closely aligned relativistic jets, i.e., blazars. One of the key research problems in jet physics is constraining the evolution of these enigmatic sources. This talk will briefly discuss some of the recent discoveries of detecting $\gamma$-ray emission from a variety of jetted AGN,...
The soft excess, an excess emission below 2 keV, is an extraordinary feature of the X-ray spectra for most of the Seyfert 1 AGNs. The origin of this feature remains debated, as several models have been suggested to explain it, including warm Comptonization, blurred ionized reflection and other models. From the long-term observations of Ark 120, a bare AGN, we found a strong correlation between...
We study the multi-wavelength properties of the bare Seyfert 1.5 galaxy MCG-2-58-22 using the multi-epoch AstroSat observations taken simultaneously in the X-ray and UV bands. Previous studies reported X-ray variability in MCG-2-58-22 on both short and long time scales. The source was in a high X-ray flux state in 2007 and 2016 with a 2-10 keV flux of ~5×10^-11 erg/cm^2/s. The AstroSat...
A detailed broadband spectral and timing analysis of a small flaring event of a120 ks in a narrow-line Seyfert 1 galaxy NGC 4051 using simultaneous XMM-Newton and NuSTAR observations has been performed. The ~300 ks long NuSTAR observation and the overlapping XMM-Newton exposure were segregated into pre-flare, flare and post-flare segments. We found that during the flare, the NuSTAR count rate...
Despite occupying ~ 40% of the local Universe, Low Luminosity Active Galactic Nuclei (LLAGNs) are less explored due to their faintness. Detection of a few in gamma rays by Fermi-LAT allows us to constrain the physical parameters of the jet by modeling their spectral energy distributions from radio to gamma-ray energies. While a one-zone model explains the broadband emission up to a few GeV,...
The radiative loss interpretation for the broken power-law spectra of blazars is often questioned since the difference between the indices does not support this inference. MKN 421 is one of the extensively studied high energy peaked blazars with its synchrotron component peaking at soft X-ray energies. The X-ray spectra, therefore, exhibits significant curvature and the spectrum is well...
The broadband spectral study of blazars has provided significant information regarding the emission processes and the blazar jet environment. Inputs derived from the temporal study are often conflicting with the processes responsible for the flux variation not being consistent with the statistical flux distribution. Besides these, even after decades of research, the matter content of blazar...
We studied the broadband X-ray spectra of Swift/BAT selected low-accreting AGNs using the observations from NuSTAR and Swift/BAT in the energy range of 3 − 150 keV. Our sample consists of 24 AGNs with Eddington ratio, $\lambda_{Edd} < 10^{−3}$. We extracted several coronal parameters from the spectral modelling, such as the photon index, hot electron plasma temperature, cutoff energy and...
Ultraluminous infrared galaxies (ULIRGs) are gas-rich merger remnants that are extremely luminous at infrared wavelengths, represent the final stage of the merging process of two comparable mass gas-rich galaxies that finally evolve into elliptical galaxies, and in some cases radio-loud AGN. Using the Giant Metrewave Radio Telescope (GMRT), we observed a large sample of ULIRGs that have...
In the radio-quiet category of active galactic nuclei (AGN), the observed X-ray emission is believed to originate in the hot corona close to the vicinity of the accretion disk. Despite the numerous X-ray studies on AGN, we still do not have a clear understanding of the nature of the corona, such as its geometry, shape, location and the physical processes that power it. Parameters that can put...
We present a multi-wavelength study of the active nucleus and the off-nuclear X-ray sources in the nearby spiral galaxy, NGC 1365 using three simultaneous UV/X-ray observations by AstroSat over a two months period and archival IR observations performed with Spitzer and Herschel. Utilising the data from the Soft X-ray Telescope (SXT) on-board AstroSat, we find spectral variability mainly caused...
