Publications of Astronomical Society of India: Recent submissions

  • Longitudinal shower development and its signature at observation level 
    Chitnis, V. R; Bhat, P. N (Astronomical Society of India, 2002)
    From a study of Cverenkov photon arrival times at various core distances at the observation level it has already been established that the photon front is well fitted with a spherical surface traveling at the speed of light ...
  • Estimation of vital shower parameters in wavefront sampling technique 
    Chitnis, V. R; Bhat, P. N (Astronomical Society of India, 2002)
    Wavefront sampling experiments record arrival times of Cverenkov photons with high precision at various locations in Cverenkov pool using a distributed array of telescopes. It was shown earlier that this photon front can ...
  • Gamma-hadron separation using Cverenkov photon density fluctuations 
    Chitnis, V. R; Bhat, P. N (Astronomical Society of India, 2002)
    In atmospheric Cverenkov technique gamma-rays are detected against abundant background produced by hadronic showers. In order to improve signal to noise ratio of the experiment, it is necessary to reject a significant ...
  • Gamma ray and hadron generated Cverenkov photon spectra at various observation altitudes 
    Rahman, M. A; Bhat, P. N; Acharya, B. S; Chitnis, V. R; Majumdar, P; Vishwanath, P. R (Astronomical Society of India, 2002)
    We have studied the propagation of Cverenkov photons generated by Very High Energy gamma-rays and hadrons in the atmosphere. Photon production height distributions derived from semi-empirical methods agree with those ...
  • Cosmic ray mass composition through Cerenkov technique - a feasibility study 
    Bhat, C. K; Kaul, R. K; Sapru, M. L; Bhat, C. L (Astronomical Society of India, 2002)
    Detailed Monte Carlo simulations of atmospheric Cerenkov events, recorded by the 349 - pixel imaging camera of the TACTIC Imaging Cerenkov Telescope array at Mt. Abu, Rajasthan, have been carried out to study the possibility ...
  • Understanding the behavior of energy X-rays from the black hole candidate GRS 1915+105 
    Nandi, A; Chakrabarti, S. K (Astronomical Society of India, 2002)
    Black Hole candidate GRS 1915+105 shows a very interesting behaviour at high energy X-rays. For instance, it shows quasi-Periodic Oscillations (QPO) only at high energies. Also the spectral slopes at high energies vary and ...
  • Analytical study of standing shocks around black hole 
    Das, S; Chakrabarti, S. K (Astronomical Society of India, 2002)
    Shocks from around black holes as the matter slows down by centifugal barrier. At the shocks, kinetic energy is converted into thermal energy and hard-X rays, outflows etc. are produced which are observed. We compute the ...
  • Wind induced instabilities in accretion flow around black holes 
    Acharya, K; Chakrabarti, S. K; Molteni, D (Astronomical Society of India, 2002)
    We identify a new type of instability of the accrelation flow which is formed due to interaction of the outgoing winds with the incoming flow. Mainly due to shear instability, the flow oscillates around the equatorial ...
  • Shocks in winds from accretion discs and the formation of high energy particles 
    Chattopadhyay, I; Chakrabarti, S. K (Astronomical Society of India, 2002)
    We study effects of radiation momentum deposition on jets and outflows from the disks and show that if disks are perturbed, jets could have propagating shock waves which may accelerate particles to observed slopes.
  • Astronomical gamma-ray lines predicting probable gamma-emitter nucleosynthesis sites as explosive events 
    Bardoloi, I; Barua, M. M (Astronomical Society of India, 2002)
    Astronomical gamma-ray (?) lines with energy 0.5 - 15 MeV have been interpreted as due to e+ - e- annihilation and decay and de-excitation of the excited nucleosynthesis yields produced in some explosive sites and then ...
  • Variability study of Mrk-421 in near IR bands from Mt. Abu observatory 
    Joshi, U. C; Baliyan, K. S; Ganesh, S (Astronomical Society of India, 2002)
    Mrk421 is the nearest, and brightest blazar detected in almost all the spectral windows, including high energy gamma-rays. It exhibits short and long timescale variations at all frequency bands. Though it has been observed ...
  • X-ray Spectroscopy of the HMXB Pulsar GX 301-2 with Chandra 
    Mukherjee, U; Paul, B (Astronomical Society of India, 2003)
    We present analysis of X-ray spectra of the accreting pulsar GX 301-2, from two observations with the Chandra X-ray observatory made during different phases of its orbital period. Analysis of the zeroth order ACIS spectra ...
  • Observations of Mkn 421 with TACTIC 
    Kaul, R. K; Bhat, C. L (Astronomical Society of India, 2002)
    The TACTIC imaging element has observed the extragalactic BL Lac object Mkn 421 for ~ 78h during Jan. - April 2001. Analysis of the overall data set, using the dynamic supercuts methodology, has revealed the presence of a ...
  • Orbital Evolution of the Binary X-ray Pulsar Her X-1 
    Bhatt, N; Paul, B; Koul, C. L (Astronomical Society of India, 2003)
    We report the discovery of a break in the orbital period evolution of Her X-1, coincident with a recent anomalous low state.
  • Of Neutrinos and Magnetars 
    Konar, S (Astronomical Society of India, 2003)
  • Observations of Markarian 421 by the CAT imaging telescope 
    Fleury, P (Astronomical Society of India, 2002)
    The CAT imaging telescope has been exploited since 1997 for the observation of Mrk-421 among other sources. After a brief review of the characteristics of the CAT telescope, the event reconstruction method will be described. ...
  • TeV Gamma-ray flares from Mkn 421 detected by the pachmarhi array of Cverenkov Telescopes 
    Bhat, P. N; Acharya, B. S; Chitnis, V. R; Majumdar, P; Rahman, M. A; Singh, B. B; Vishwanath, P. R (Astronomical Society of India, 2002)
    Pachmarhi Array of Cverenkov Telescopes (PACT), based on wavefront sampling technique, has been used for detecting TeV gamma rays from galactic and extra-galactic ?-ray sources. The Blaar, Mkn 421 was one such extra-galactic ...
  • Observations of Mrk 421 with the CELESTE Heliostat array 
    Le Gallou, R; Smith, D. A (Astronomical Society of India, 2002)
    Since CELESTE first began routine observations in November 1999 in the 50 GeV range Mrk 421 has been a prime target. Here we report the preliminary average integral flux measurement obtained with 31.5 hours of ON-source ...
  • The Magnetar Fields 
    Konar, S (Astronomical Society of India, 2003)
    We discuss the nature of evolution of the magnetic field in magnetars
  • Introduction to Markarian 421 special session 
    Fleury, P (Astronomical Society of India, 2002)

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