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Browsing by Author "Sahayanathan, S"

Browsing by Author "Sahayanathan, S"

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  • Adiabatic cooling and nonthermal spectrum of blazars 
    Sahayanathan, S; Bhattacharyya, S; Kaul, C. L; Bhat, C. L (Astronomical Society of India, 2001)
    Here we study the effect of adiabatic cooling on the non-thermal synchrotron spectra of blazars from radio to X-ray region resulting when blazars are in the flaring state.
  • Awakening of the high-redshift blazar CGRaBS J0809+5341 
    Paliya, Vaidehi S; Parker, M. L; Stalin, C. S; Fabian, A. C; Ramya, S; Covino, S; Tagliaferri, G; Sahayanathan, S; Ravikumar, C. D (IOP Publishing, 2015-04)
    CGRaBS J0809+5341, a high-redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by ~5 mag and reached an unfiltered apparent magnitude of 15.7 mag. This implies an absolute ...
  • Correlation between optical and γ -ray flux variations in bright flat spectrum radio quasars 
    Rajput, Bhoomika; Stalin, C. S; Sahayanathan, S (Oxford University Press on behalf of the Royal Astronomical Society, 2020-11)
    Blazars are known to show flux variations over a range of energies from low-energy radio to high-energy γ-rays. Cross-correlation analysis of the optical and γ-ray light curves in blazars shows that flux variations are ...
  • Correlation between optical and γ-ray flux variations in BL Lacs 
    Rajput, Bhoomika; Shah, Zahir; Stalin, C. S; Sahayanathan, S; Rakshit, S (Oxford University Press on behalf of the Royal Astronomical Society, 2021-06)
    We report here results of the analysis of correlated flux variations between the optical and GeV γ-ray bands in three bright BL Lac objects, namely AO 0235+164, OJ 287, and PKS 2155−304. This was based on the analysis of ...
  • Energy Sensitive Search for Pulsed Photons from Crab Pulsar using the TACTIC Imaging Element 
    Rannot, R. C; Yadav, K. K; Dhar, V. K; Tickoo, A. K; Bhatt, N; Bhattacharyya, S; Chandra, P; Goyal, H. C; Kaul, C. L; Kaul, R. K; Kothari, M; Kotwal, S; Koul, R; Sahayanathan, S; Sapru, M. L; Sharma, M; Venugopal, K; Bhat, C. L (Astronomical Society of India, 2003)
    The Imaging Element (IE) of the 4-element TACTIC array of atmospheric Cherenkov telescopes is in operation at Mt. Abu Rajasthan, in Western India. We have successfully detected a steady signal from the Crab Nebula at a ...
  • An Expanding Plasma Model for the X-ray/radio knots in KPC-scale Jets of Active Galactic Nuclei 
    Sahayanathan, S; Misra, R; Kembhavi, A. K; Kaul, C. L (Astronomical Society of India, 2003)
    We model the observed X-ray/radio knots in Active Galactic Nuclei (AGN) as isotropically expanding spherical plasma clouds fed continously by non-thermal electrons. The time-dependent electron distribution and the emitted ...
  • Large-Area Wide Angle (LAWA) cerenkov detector for MYSTIQUE array 
    Kamath, K; Bhattacharyya, S; Dhar, V. K; Darzi, M. A; Kaul, S. R; Kaul, R. K; Koul, R; Sahayanathan, S; Tickoo, A. K; Wani, A. M; Bhat, C. L (Astronomical Society of India, 2002)
    An ultra-sensitive, multidetector wide angle atmospheric Cerenkov telescope array is being set up at Mt. Abu for cosnic gamma-ray studies in tens of TeV energy region. The design features of the Cerenkov light detector, ...
  • 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 ...
  • 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 ...
  • On the Spectral Curvature of VHE Blazar 1ES 1011 + 496: Effect of Spatial Particle Diffusion 
    Sinha, A; Sahayanathan, S; Acharya, B. S; Anupama, G. C; Chitnis, V. R; Singh, B. B (IOP Publishing, 2017-02-10)
    The American Astronomical Society, find out more The Institute of Physics, find out more On the Spectral Curvature of VHE Blazar 1ES 1011+496: Effect of Spatial Particle Diffusion Atreyee Sinha1, S. ...
  • The peculiar radio-loud narrow line seyfert 1 galaxy 1H 0323+342 
    Paliya, Vaidehi S; Sahayanathan, S; Parker, M. L; Fabian, A. C; Stalin, C. S; Anjum, A; Pandey, S. B (IOP Publishing, 2014-07-10)
    We present a multi-wavelength study of the radio-loud narrow line Seyfert 1 galaxy (NLSy1), 1H 0323+342, detected by Fermi Gamma Ray Space Telescope. Multi-band light curves show many orphan X-ray and optical flares having ...
  • Recent observations of lES2344+514 and PSR 0355+54 with TACTIC Imaging Element 
    Tickoo, A. K; Dhar, V. K; Yadav, K. K; Rannot, R. C; Bhattacharyya, S; Chandra, P; Goyal, H. C; Kaul, C. L; Kaul, R. K; Kothari, M; Kotwal, S; Koul, R; Sahayanathan, S; Sapru, M. L; Sharma, M; Venugopal, K; Bhatt, N; Bhatt, C. L (Astronomical Society of India, 2002-09)
    The TACTIC Imaging Element has observed the active galaxy 1ES 2344+514 and the pulsar PSR 0355+54 during Oct-Nov, 2001. Analysis of the recorded events, collected for a period of 70 hours on both these sources reveals ...
  • Search for pulsed Te V gamma- rays from Crab pulsar with the TACTIC Imaging gamma-ray Telescope 
    Rannot, R. C; Yadav, K. K; Dhar, V. K; Tickoo, A. K; Bhatt, N; Bhattacharyya, S; Chandra, P; Goyal, H. C; Kaul, C. L; Kaul, R. K; Kothari, M; Kotwal, S; Koul, R; Sahayanathan, S; Sapru, M. L; Sharma, M; Venugopal, K; Bhat, C. L (Astronomical Society of India, 2002-09)
    The TACTIC Imaging Element has observed Crab Nebula/pulsar for a total. of about 40 hours during Jan.- Mar. 2001. Preliminary results do not show any evidence of the 33 ms pulsations from the pulsar direction at an energy ...
  • Temporal correlation between the optical and γ-ray flux variations in the blazar 3C 454.3 
    Rajput, Bhoomika; Stalin, C. S; Sahayanathan, S; Rakshit, S; Amit Kumar Mandal (Oxford University Press on behalf of the Royal Astronomical Society, 2019-06)
    Blazars show optical and γ-ray flux variations that are generally correlated, although there are exceptions. Here we present anomalous behaviour seen in the blazar 3C 454.3 based on an analysis of quasi-simultaneous data ...
  • The violent hard X-ray variability of MRK 421 observed by Nustar in 2013 April 
    Paliya, Vaidehi S; Bottcher, M; Diltz, C; Stalin, C. S; Sahayanathan, S; Ravikumar, C. D (IOP Publishing, 2015-10-01)
    The well-studied blazar Markarian 421 (Mrk 421, z = 0.031) was the subject of an intensive multi-wavelength campaign when it flared in 2013 April. The recorded X-ray and very high-energy (E > 100 GeV) γ-ray fluxes are the ...

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