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Browsing by Author "Stalin, C. S"

Browsing by Author "Stalin, C. S"

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  • Intra-night optical variability of misaligned active galaxies 
    Bhattacharya, Debbijoy; Gulati, S; Stalin, C. S (Oxford University Press on behalf of the Royal Astronomical Society, 2019-03)
    The majority of the γ-ray sources detected by the Fermi Gamma-ray Space Telescope belong to the blazar class of active galactic nuclei (AGNs). In addition to blazars, a minority of non-blazar AGNs is also found to be γ-ray ...
  • Intranight optical variability of γ -ray-loud narrow-line Seyfert 1 galaxies 
    Paliya, Vaidehi S; Stalin, C. S; Kumar, Brijesh; Kumar, Brajesh; Bhatt, V. K; Pandey, S. B; Yadav, K. S (Oxford University Press on behalf of the Royal Astronomical Society, 2013-01-21)
    The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope has detected γ-ray emission in about half a dozen narrow-line Seyfert 1 (NLSy1) galaxies. This indicates the presence of relativistic jets in these ...
  • Investigation of the correlation between optical and γ-ray flux variation in the blazar Ton 599 
    Rajput, Bhoomika; Mandal, Amit Kumar; Pandey, Ashwani; Stalin, C. S; Max-Moerbeck, Walter; Mathew, Blesson (Published by Oxford University Press on behalf of Royal Astronomical Society, 2024-02)
    The correlation between optical and γ-ray flux variations in blazars reveals a complex behaviour. In this study, we present our analysis of the connection between changes in optical and γ-ray emissions in the blazar Ton ...
  • Leptonic and hadronic modeling of Fermi-LAT hard spectrum quasars and predictions for high-energy polarization 
    Paliya, Vaidehi S; Zhang, H; Bottcher, M; Ajello, M; Domi­nguez, A; Joshi, M; Hartmann, D; Stalin, C. S (IOP Publishing, 2018-08)
    We present the results of a study of the time-averaged spectral energy distributions (SEDs) of eight flat spectrum radio quasars (FSRQs) present in the second catalog of high energy sources detected beyond 50 GeV by the ...
  • Lepto−Hadronic Origin of γ-ray Outbursts of 3C 279 
    Paliya, Vaidehi S; Diltz, C; Bottcher, M; Stalin, C. S; Buckley, D (Astronomical Society of India, 2015-03)
    The blazar 3C 279 exhibited a giant γ-ray outburst in 2013 December and 2014 April. Apart from the very fast γ-ray flux variability, the spectral nature of the flares were also found to vary significantly between these ...
  • Long term γ-ray variability of blazars 
    Rajput, Bhoomika; Stalin, C. S; Rakshit, S (EDP Sciences, 2020-02)
    We used the data from the Fermi Gamma-ray Space Telescope to characterise the γ-ray flux variability of blazars on month-like time scales. Our sample consists of 1120 blazars of which 481 are flat spectrum radio quasars ...
  • Long-Term Monitoring of Blazar PKS 0208-512: A Change of γ-Ray Baseline Activity from EGRET to Fermi Era 
    Ammenadka, Krishna Mohana; Bhattacharya, Debbijoy; Bhattacharyya, Subir; Bhatt, N; Stalin, C. S (Multidisciplinary Digital Publishing Institute, 2022-10)
    The blazar PKS 0208-512 was in the lowest 𝛾 -ray brightness state during the initial 10 years of observations with the Fermi Gamma-ray Space Telescope (Fermi), which was an order of magnitude lower than its flux state ...
  • Long-term optical and infrared variability characteristics of Fermi blazars 
    Safna, P. Z; Stalin, C. S; Rakshit, S; Mathew, Blesson (Oxford University Press on behalf of the Royal Astronomical Society, 2020-11)
    We present long-term optical and near-infrared flux variability analysis of 37 blazars detected in the γ-ray band by the Fermi Gamma-Ray Space Telescope. Among them, 30 are flat spectrum radio quasars (FSRQs) and 7 are BL ...
  • Long-term optical flux and colour variability in quasars 
    Sukanya, N; Stalin, C. S; Jeyakumar, S; Praveen, D; Dhani, A; Damle, R (IOP Publishing, 2016-02)
    We have used optical V and R band observations from the Massive Compact Halo Object (MACHO) project on a sample of 59 quasars behind the Magellan ic clouds to study their long term optical flux and colour ...
  • Long-term ultraviolet variability of Seyfert galaxies 
    Sukanya, N; Stalin, C. S; Joseph, P; Rakshit, S; Praveen, D; Damle, R (Indian Academy of Sciences, 2018-12)
    Flux variability is one of the defining characteristics of Seyfert galaxies, a class of active galactic nuclei (AGN). Although these variations are observed over a wide range of wavelengths, results on their flux variability ...
  • Long-term ultraviolet variability of Seyfert galaxies 
    Sukanya, N; Stalin, C. S; Joseph, P; Rakshit, S; Praveen, D; Damle, R (Indian Academy of Sciences, 2018-12)
    Flux variability is one of the defining characteristics of Seyfert galaxies, a class of active galactic nuclei (AGN). Although these variations are observed over a wide range of wavelengths, results on their flux variability ...
  • Mass of the black hole in the Seyfert 1.5 galaxy H 0507+164 from reverberation mapping 
    Stalin, C. S; Jeyakumar, S; Coziol, R; Pawase, R. S; Thakur, S. S (Wiley-Blackwell, 2011-09)
    We present the results of our optical monitoring campaign of the X-ray source H 0507+164, a low-luminosity Seyfert 1.5 galaxy at a redshift z= 0.018. Spectroscopic observations were carried out during 22 nights in 2007, ...
  • Measurement of coronal properties of Seyfert galaxies from NuSTAR’s hard X-ray spectrum 
    Priyanka Rani; Stalin, C. S (Indian Academy of Sciences, 2018-02)
    Precise measurement of the coronal properties of Active Galactic Nuclei (AGN) requires the availability of high signal-to-noise ratio data covering a wide range of X-ray energies. The Nuclear Spectroscopic Telescope Array ...
  • Mid-infrared variability of γ-ray emitting blazars 
    Anjum, A; Stalin, C. S; Rakshit, S; Gudennavar, S. B; Durgapal, A (Oxford University Press on behalf of the Royal Astronomical Society, 2020-05)
    Using data from the Wide-field Infrared Survey Explorer, we studied the mid-infrared (mid-IR) 3.4 μm (W1-band) and 4.6 μm (W2-band) flux variability of γ-ray emitting blazars. Our sample consists of 460 flat spectrum radio ...
  • Multi-epoch intranight optical monitoring of eight radio-quiet BL Lac candidates 
    Kumar, P; Gopal-Krishna; Stalin, C. S; Chand, H; Srianand, R; Petitjean, P (Oxford University Press on behalf of the Royal Astronomical Society, 2017-10)
    For a new sample of eight weak-line quasars (WLQs) we report a sensitive search in 20 intranight monitoring sessions, for blazar-like optical flux variations on hour-like and longer time-scale (day/month/year-like). The ...
  • Multi-wavelength observations of 3C 279 during the extremely bright gamma-ray flare in 2014 March-April 
    Paliya, Vaidehi S; Sahayanathan, S; Stalin, C. S (IOP Publishing, 2015-04)
    The well-studied blazar 3C 279 underwent a giant γ-ray outburst in 2014 March–April. The measured γ-ray flux is the highest detected from 3C 279 by the Fermi Large Area Telescope. Hour scale γ-ray flux variability is ...
  • Multiwavelength monitoring of NGC 1275 over a decade: evidence of a shift in synchrotron peak frequency and long-term multiband flux increase 
    Gulati, Sanna; Bhattacharya, Debbijoy; Bhattacharyya, Subir; Bhatt, N; Stalin, C. S; Agrawal, V. K (Oxford University Press on behalf of the Royal Astronomical Society, 2021-05)
    We carried out a detailed study of the temporal and broad-band spectral behaviour of one of the brightest misaligned active galaxies in γ-rays, NGC 1275, utilizing 11 years of Fermi data and the available Swift and AstroSat ...
  • Multiwavelength study of different flaring and low-activity states of blazar 4C+21.35 
    Bhattacharya, D; Krishna Mohana, A; Bhattacharyya, S; Bhatt, N; Stalin, C. S (Oxford University Press on behalf of the Royal Astronomical Society, 2021-01)
    Blazars, a class of active galactic nuclei, emit over the entire accessible electromagnetic spectrum and modelling of their broad-band spectral energy distribution (SED) is the key to constrain the underlying emission ...
  • Multiwavelength study of radio galaxy Pictor A: detection of western hotspot in far-UV and possible origin of high energy emissions 
    Gulati, Sanna; Bhattacharya, Debbijoy; Ramadevi, M. C; Stalin, C. S; Sreekumar, P (Oxford University Press on behalf of Royal Astronomical Society, 2023-05)
    A comprehensive study of the nucleus and western hotspot of Pictor A is carried out using AstroSat observations, 13 yr of Fermi, and archival Swift observations along with other published data. We report the first detection ...
  • A multiwavelength study of the flat-spectrum radio quasar NVSS J141922−083830 covering four flaring episodes 
    Buckley, D. A. H; Britto, R. J; Chandra, S; Krushinsky, V; Bottcher, M; Razzaque, S; Lipunov, V; Stalin, C. S; Gorbovskoy, E; Tiurina, N; Vlasenko, D; Kniazev, A (Oxford University Press on behalf of Royal Astronomical Society, 2022-12)
    We present multiwavelength observations and a model for flat-spectrum radio quasar (FSRQ) NVSS J141922−083830, originally classified as a blazar candidate of unknown type (BCU II object) in the Third Fermi-LAT AGN Catalog. ...

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