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Browsing by Author "Stalin, C. S"

Browsing by Author "Stalin, C. S"

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  • 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. ...
  • Narrow-line Seyfert 1 galaxies in Sloan Digital Sky Survey: a new optical spectroscopic catalogue 
    Paliya, Vaidehi S; Stalin, C. S; Dominguez, Alberto; Saikia, D. J (Oxford University Press on behalf of Royal Astronomical Society, 2024-01)
    Narrow-line Seyfert 1 (NLSy1) galaxies are an enigmatic class of active galactic nuclei (AGN) that exhibit peculiar multiwavelength properties across the electromagnetic spectrum. For example, these sources have allowed ...
  • The Nature of γ -ray loud Narrow-line Seyfert I Galaxies PKS 1502+036 And PKS 2004-447 
    Paliya, Vaidehi S; Stalin, C. S; Shukla, A; Sahayanathan, S (IOP Publishing, 2013-05-01)
    Variable γ-ray emission has been discovered in five radio-loud narrow-line Seyfert 1 (NLSy1) galaxies by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. This has clearly demonstrated that these NLSy1 ...
  • Night sky at the Indian Astronomical Observatory during 2000-2008 
    Stalin, C. S; Hegde, M; Sahu, D. K; Parihar, P. S; Anupama, G. C; Bhatt, B. C; Prabhu, T. P (Astronomical Society of India, 2008-09)
    This paper presents an analysis of the optical night sky brightness and extinction coefficient measurements in UBVRI at the Indian Astronomical Observatory (IAO), Hanle, during the period 2000–2008. They are obtained from ...

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