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Browsing by Author "Stalin, C. S"

Browsing by Author "Stalin, C. S"

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  • 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 ...
  • Noise modeling and analysis of an IMU-based attitude sensor: improvement of performance by filtering and sensor fusion 
    Subramaniam, A; Sindhu, N; Tandon, S. N; Kameswara Rao, N; Postma, J; Cote, Patrick; Hutchings, J. B; Ghosh, S. K; George, K; Girish, V; Mohan, Rekhesh; Murthy, J; Sankarasubramanian, K; Stalin, C. S; Sutaria, F. K; Mondal, Chayan; Snehalata Sahu (SPIE-The International Society for Optical Engineering, 2016-07)
    We describe the characterization and removal of noises present in the Inertial Measurement Unit (IMU) MPU- 6050, which was initially used in an attitude sensor, and later used in the development of a pointing system for ...
  • NuSTAR spectral analysis of three Seyfert galaxies: NGC 3227, NGC 5548, and MR 2251−178 
    Pal, Indrani; Stalin, C. S; Mallick, L; Priyanka Rani (EDP Sciences, 2022-06)
    Context. The observed nuclear X-ray emission in the radio-quiet category of active galactic nuclei (AGN) is believed to be from a compact region, the corona, which is situated in the vicinity of central supermassive black ...
  • Obscured and powerful AGN and starburst activities at z ~ 3.5 
    Polletta, M; Omont, A; Berta, S; Bergeron, J; Stalin, C. S; Petitjean, P; Giorgetti, M; Trinchieri, G; Srianand, R; McCracken, H. J; Pei, Y; Dannerbauer, H (EDP Sciences, 2008-12)
    Aims. Short phases of coeval powerful starburst and AGN activity during the lifetimes of the most massive galaxies are predicted by various models of galaxy formation and evolution. In spite of their recurrence and high ...
  • On the origin of core radio emissions from black hole sources in the realm of relativistic shocked accretion flow 
    Das, Santabrata; Nandi, Anuj; Stalin, C. S; Rakshit, Suvendu; Dihingia, Indu Kalpa; Singh, Swapnil; Aktar, Ramiz; Mitra, Samik (Oxford University Press on behalf of Royal Astronomical Society, 2022-08)
    We study the relativistic, inviscid, advective accretion flow around the black holes and investigate a key feature of the accretion flow, namely the shock waves. We observe that the shock-induced accretion solutions are ...
  • On the Origin of Gamma-Ray Flares from Bright Fermi Blazars 
    Paliya, Vaidehi S; Böttcher, M; Gurwell, Mark; Stalin, C. S (IOP Publishing, 2021-12)
    The origin of γ-ray flares observed from blazars is one of the major mysteries in jet physics. We have attempted to address this problem following a novel spectral energy distribution (SED) fitting technique that explored ...
  • On the Photometric Error Calibration for the Differential Light Curves of Point-like Active Galactic Nuclei 
    Goyal, Arti; Mhaskey, Mukul; Gopal-Krishna; Witta, P. J; Stalin, C. S; Sagar, R (Indian Academy of Sciences, 2013-09)
    It is important to quantify the underestimation of rms photometric errors returned by the commonly used APPHOT algorithm in the IRAF software, in the context of differential photometry of point-like AGN, because of the ...
  • Optical and GeV flux variations in Fermi blazars 
    Stalin, C. S (Astronomical Society of India, 2015-04)
    A large fraction of γ-ray emitting blazars show correlated flux variations in the optical and γ-ray bands with little or no time lag. However, in a minority of them, uncorrelated optical and γ-ray flux variations are seen. ...
  • Optical and radio observations of the bright GRB 010222 afterglow: evidence for rapid synchrotron cooling ? 
    Sagar, R; Stalin, C. S; Bhattacharya, D; Pandey, S. B; Mohan, V; Castro-Tirado, A. J; Pramesh Rao, A; Trushkin, S. A; Nizhelskij, N. A; Bremer, M; Castro Ceron, J. M (Astronomical Society of India, 2001)
    We report photometric observations of the optical afterglow of GRB 010222 in V, R and I passbands carried out between 22-27 February 2001 at Nainital. We determine the CCD Johnson BV and Cousins RI photometric magnitudes ...
  • Optical identification of XMM sources in the Canada-France-Hawaii telescope legacy survey 
    Stalin, C. S; Petitjean, P; Srianand, R; Fox, A. J; Coppolani, F; Schwope, A (Blackwell Publishing, 2010-01)
    We present optical spectroscopic identifications of X-ray sources in similar to 3 deg2 of the XMM-Large Scale Structure survey (XMM-LSS), also covered by the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), obtained ...
  • Optical variability of narrow-line and broad-line Seyfert 1 galaxies 
    Rakshit, S; Stalin, C. S (IOP Publishing, 2017-05)
    We studied the optical variability ( OV ) of a large sample of narrow-line Seyfert 1 ( NLSy1 ) and broad-line Seyfert 1 ( BLSy1 ) galaxies with z  <  0.8 to investigate any differences in their OV ...
  • Origin of the broadband emission from the transition blazar B2 1308+326 
    Pandey, Ashwani; Kushwaha, Pankaj; Wiita, Paul J; Prince, Raj; Czerny, Bożena; Stalin, C. S (EDP Sciences, 2024-01)
    Context. Transition blazars exhibit a shift from one subclass to the next during different flux states. It is therefore crucial to study them to understand the underlying physics of blazars. Aims. We probe the origin of ...

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