C. S. Stalin
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View article: Spectroscopic Reverberation Mapping for SARM: The Case of Mrk 1048 and Mrk 618
Spectroscopic Reverberation Mapping for SARM: The Case of Mrk 1048 and Mrk 618 Open
Robust extragalactic distance measurements are crucial for resolving the persistent discrepancy in the value of the Hubble constant ( H 0 ). Active galactic nuclei (AGNs), through their compact and variable broad-line regions, enable the d…
View article: Discovery of Changing-look Behavior in AGN NGC 3822: A Long-term Multiwavelength Study
Discovery of Changing-look Behavior in AGN NGC 3822: A Long-term Multiwavelength Study Open
We present a comprehensive long-term multiwavelength study of the active galactic nucleus NGC 3822, based on 17 yr (2008–2025) of X-ray, ultraviolet (UV), and optical observations. The data set includes observations from Swift , XMM - Newt…
View article: Spectroscopic Reverberation Mapping for SARM: The Case of Mrk 1048 and Mrk 618
Spectroscopic Reverberation Mapping for SARM: The Case of Mrk 1048 and Mrk 618 Open
Robust extragalactic distance measurements are crucial for resolving the persistent discrepancy in the value of the Hubble constant (H$_0$)). Active Galactic Nuclei (AGNs), through their compact and variable broad-line regions (BLRs), enab…
View article: Clues on the X-ray emission mechanism of blazars PKS 2155$-$304 and 3C 454.3 through polarization studies
Clues on the X-ray emission mechanism of blazars PKS 2155$-$304 and 3C 454.3 through polarization studies Open
X-ray polarization measurable with the imaging X-ray Polarimetry Explorer (\textit{IXPE}) could constrain the long-debated leptonic versus hadronic origin of the high-energy component in the broadband spectral energy distribution (SED) of …
View article: The Detection of Teraelectronvolt Radiation from a Flat-spectrum Radio Quasar
The Detection of Teraelectronvolt Radiation from a Flat-spectrum Radio Quasar Open
The very high-energy (VHE; >100 GeV) radiation carries the signatures of the matter–energy interaction in some of the most extreme astrophysical environments. Considering broad emission line blazars, i.e., flat-spectrum radio quasars (FSRQ…
View article: Radio Morphology of Gamma-Ray Sources. II. Giant Radio Galaxies
Radio Morphology of Gamma-Ray Sources. II. Giant Radio Galaxies Open
Giant radio sources, including galaxies and quasars (hereafter GRSs), are active galactic nuclei (AGN) hosting relativistic jets with source sizes exceeding a projected length of 0.7 Mpc. They are crucial to understanding the evolution of …
View article: Radio Morphology of Gamma-ray Sources -- II. Giant Radio Galaxies
Radio Morphology of Gamma-ray Sources -- II. Giant Radio Galaxies Open
Giant radio sources, including galaxies and quasars (hereafter GRGs), are active galactic nuclei (AGN) hosting relativistic jets with source sizes exceeding the projected length of 0.7 Mpc. They are crucial to understanding the evolution o…
View article: The long-term optical flux variations of Compact Symmetric Objects
The long-term optical flux variations of Compact Symmetric Objects Open
Compact Symmetric Objects (CSOs) are a distinct category of jetted active galactic nuclei (AGN) whose optical variability characteristics have not been well investigated. We present here the results of our investigation on the optical flux…
View article: Warm Ionized Gas Outflows in Active Galactic Nuclei: What Causes Them?
Warm Ionized Gas Outflows in Active Galactic Nuclei: What Causes Them? Open
The driving force behind outflows, often invoked to understand the correlation between the supermassive black holes powering active galactic nuclei (AGN) and their host galaxy properties, remains uncertain. We provide new insights into the…
View article: Study of giant radio galaxies using spectroscopic observations from the Himalayan Chandra Telescope
Study of giant radio galaxies using spectroscopic observations from the Himalayan Chandra Telescope Open
We present the results of spectroscopic observations of host galaxies of eleven candidate giant radio galaxies (GRGs), powered by active galactic nuclei (AGNs), conducted with the 2-m Himalayan Chandra Telescope (HCT). The primary aim of t…
View article: Study of giant radio galaxies using spectroscopic observations from the Himalayan Chandra Telescope
Study of giant radio galaxies using spectroscopic observations from the Himalayan Chandra Telescope Open
We present the results of spectroscopic observations of host galaxies of eleven candidate giant radio galaxies (GRGs), powered by active galactic nuclei (AGNs), conducted with the 2-m Himalayan Chandra Telescope (HCT). The primary aim of t…
View article: DA 362: A Gamma-Ray-emitting Compact Symmetric Object
DA 362: A Gamma-Ray-emitting Compact Symmetric Object Open
The γ -ray detection from an astrophysical object indicates the presence of an extreme environment where high-energy radiation is produced. With the continuous monitoring of the γ -ray sky by the Fermi Large Area Telescope (LAT) leading to…
View article: X-ray timing and spectral characteristics of compact symmetric objects
X-ray timing and spectral characteristics of compact symmetric objects Open
Compact Symmetric Objects (CSOs) are a distinct category of jetted active galactic nuclei whose high-energy emission is not well understood. We examined the X-ray characteristics of 17 bona fide CSOs using observations from Chandra, XMM–Ne…
View article: Radio Morphology of Gamma-Ray Sources: Double-lobed Radio Sources
Radio Morphology of Gamma-Ray Sources: Double-lobed Radio Sources Open
The extragalactic γ -ray sky is dominated by relativistic jets aligned to the observer’s line of sight, i.e., blazars. A few of their misaligned counterparts, e.g., radio galaxies, are also detected with the Fermi-Large Area Telescope (LAT…
View article: Simultaneous X-Ray and Optical Polarization Observations of the Blazar Mrk 421
Simultaneous X-Ray and Optical Polarization Observations of the Blazar Mrk 421 Open
We present near-simultaneous X-ray and optical polarization measurements in the high synchrotron peaked (HSP) blazar Mrk 421. The X-ray polarimetric observations were carried out using Imaging X-ray Polarimetry Explorer (IXPE) on 2023 Dece…
View article: Spectrophotometric Reverberation Mapping of Intermediate-mass Black Hole NGC 4395
Spectrophotometric Reverberation Mapping of Intermediate-mass Black Hole NGC 4395 Open
Understanding the origins of massive black hole seeds and their coevolution with their host galaxy requires studying intermediate-mass black holes (IMBHs) and estimating their mass. However, measuring the masses of these IMBHs is challengi…
View article: Ultraviolet Flux and Spectral Variability Study of Blazars Observed with UVIT/AstroSat
Ultraviolet Flux and Spectral Variability Study of Blazars Observed with UVIT/AstroSat Open
Blazars, the peculiar class of active galactic nuclei, are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wavelength…
View article: Exploring the central region of NGC 1365 in the ultraviolet domain
Exploring the central region of NGC 1365 in the ultraviolet domain Open
Active galactic nuclei (AGN) feedback and its impact on their host galaxies are critical to our understanding of galaxy evolution. Here, we present a combined analysis of new high resolution ultraviolet (UV) data from the Ultraviolet Imagi…
View article: Exploring the Central Region of NGC 1365 in the Ultraviolet Domain
Exploring the Central Region of NGC 1365 in the Ultraviolet Domain Open
Active galactic nuclei (AGN) feedback and its impact on their host galaxies are critical to our understanding of galaxy evolution. Here, we present a combined analysis of new high resolution ultraviolet (UV) data from the Ultraviolet Imagi…
View article: Simultaneous X-ray and optical polarization observations of the blazar Mrk 421
Simultaneous X-ray and optical polarization observations of the blazar Mrk 421 Open
We present near-simultaneous X-ray and optical polarization measurements in the high synchrotron peaked (HSP) blazar Mrk 421. The X-ray polarimetric observations were carried out using {\it Imaging X-ray Polarimetry Explorer} ({\it IXPE}) …
View article: Spectrophotometric reverberation mapping of Intermediate-mass black hole NGC 4395
Spectrophotometric reverberation mapping of Intermediate-mass black hole NGC 4395 Open
Understanding the origins of massive black hole seeds and their co-evolution with their host galaxy requires studying intermediate-mass black holes (IMBHs) and estimating their mass. However, measuring the mass of these IMBHs is challengin…
View article: UVIT Survey of the Host Galaxies of Active Galactic Nuclei. I. Star Formation Scenarios
UVIT Survey of the Host Galaxies of Active Galactic Nuclei. I. Star Formation Scenarios Open
Circumnuclear star formation (SF) is generally seen in galaxies hosting active galactic nuclei (AGN); however, the connection between the AGN activity and SF in them is less well understood. To explore this connection on scales of a few te…
View article: Detection of a new sample of Galactic white dwarfs in the direction of the Small Magellanic Cloud
Detection of a new sample of Galactic white dwarfs in the direction of the Small Magellanic Cloud Open
Aims. In this study, we demonstrate the efficacy of the Ultraviolet Imaging Telescope (UVIT) in identifying and characterizing white dwarfs (WDs) within the Milky Way Galaxy. Methods. Leveraging the UVIT point-source catalogue towards the …
View article: Ultraviolet flux and spectral variability study of blazars observed with UVIT/AstroSat
Ultraviolet flux and spectral variability study of blazars observed with UVIT/AstroSat Open
Blazars, the peculiar class of active galactic nuclei (AGN), are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wave…
View article: Spectropolarimetric view of the gamma-ray emitting NLS1 1H0323 + 342
Spectropolarimetric view of the gamma-ray emitting NLS1 1H0323 + 342 Open
The gamma-ray emitting narrow-line Seyfert 1 galaxies are a unique class of objects that launch powerful jets from relatively lower-mass black hole systems compared to the Blazars. However, the black hole masses estimated from the total fl…
View article: Revisiting the Dust Torus Size–Luminosity Relation Based on a Uniform Reverberation-mapping Analysis
Revisiting the Dust Torus Size–Luminosity Relation Based on a Uniform Reverberation-mapping Analysis Open
We investigate the torus size–luminosity relation of Type 1 active galactic nuclei (AGNs) based on the reverberation-mapping analysis using the light curves of the optical continuum and the IR continuum obtained with the W1 and W2 bands of…
View article: A comparative analysis of the active galactic nucleus and star formation characteristics of broad- and narrow-line Seyfert 1 galaxies
A comparative analysis of the active galactic nucleus and star formation characteristics of broad- and narrow-line Seyfert 1 galaxies Open
We report here our comparative analysis of the active galactic nucleus (AGN) and star formation (SF) characteristics of a sample of narrow-line Seyfert 1 (NLS1) and broad-line Seyfert 1 (BLS1) galaxies. Our sample consisted of 373 BLS1 and…
View article: Revisiting the dust torus size-luminosity relation based on a uniform reverberation mapping analysis
Revisiting the dust torus size-luminosity relation based on a uniform reverberation mapping analysis Open
We investigate the torus size -- luminosity relation of Type 1 AGNs based on the reverberation-mapping analysis using the light curves of the optical continuum and the IR continuum obtained with the W1 and W2-bands of the Wide-field Infrar…
View article: Multiwavelength spectral modelling of the candidate neutrino blazar PKS 0735+178
Multiwavelength spectral modelling of the candidate neutrino blazar PKS 0735+178 Open
The BL Lac object PKS 0735+178 was in its historic γ-ray brightness state during 2021 December. This period also coincides with the detection of a neutrino event IC 211208A, which was localized close to the vicinity of PKS 0735+178. We car…
View article: Multi-wavelength spectral modelling of the candidate neutrino blazar PKS 0735+178
Multi-wavelength spectral modelling of the candidate neutrino blazar PKS 0735+178 Open
The BL Lac object PKS 0735+178 was in its historic $γ$-ray brightness state during December 2021. This period also coincides with the detection of a neutrino event IC211208A, which was localized close to the vicinity of PKS 0735+178. We ca…