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Browsing by Author "Bhattacharjee, P"

Browsing by Author "Bhattacharjee, P"

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  • Data analysis method for the search of point sources of gamma rays with the HAGAR telescope array 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhattacharjee, P; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Mahesh, P. K; Manoharan, J; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; Rao, S. K; Saha, L; Saleem, F; Saxena, A. K; Sharma, S. K; Shukla, A; Singh, B. B; Srinivasan, R; Srinivasulu, G; Sudersanan, P. V; Tsewang, D; Upadhya, S. S; Vishwanath, P. R (French Society of Astronomy and Astrophysics, 2011-12)
    The High Altitude GAmma-Ray (HAGAR) experiment is the highest altitude atmospheric Cherenkov sampling array, set up at 4300 m amsl in the Himalayas (Northern India). It constitutes 7 telescopes, each one with seven 90 ...
  • Detection of dark matter in the galactic halo 
    Bhattacharjee, P (Indian Academy of Sciences, 1994-02)
  • Dispersion Velocity of Galactic Dark Matter Particles 
    Cowsik, R; Ratnam, C; Bhattacharjee, P (The American Physical Society, 1996-05)
    The self-consistent spatial distribution of particles of galactic dark matter is derived including their own gravitational potential, as also of that of the visible matter of the Galaxy. In order to reproduce the observed ...
  • Dispersion velocity of Galactic dark matter particles- Reply 
    Cowsik, R; Ratnam, C; Bhattacharjee, P (The American Physical Society, 1997-03)
    A Reply to the Comment by N. W. Evans. Also, Evalyn Gates, Marc Kamionkowski, and Michael S. Turner.
  • Dynamics of dwarf-spheroidals and the dark matter halo of the galaxy 
    Cowsik, R; Ratnam, C; Bhattacharjee, P; Majumdar, S (Elsevier B. V., 2007-08)
    The dynamics of the dwarf-spheroidal (dSph) galaxies in the gravitational field of the Galaxy is investigated with particular reference to their susceptibility to tidal break-up. Based on the observed paucity of the dSphs ...
  • Extreme-energy cosmic rays: hints to new physics beyond the standard model? 
    Bhattacharjee, P; Sigl, G (Springer, 2001)
    The observed extreme energy cosmic ray (EECR) events above 10(20) eV are difficult to explain within tile standard scenario of origin of cosmic rays in which charged particles are accelerated in magnetized shocks in powerful ...
  • A Gap in the Highest Energy Cosmic Ray Spectrum as a Signature of Unification Scale Physics 
    Sigl, G; Lee, S; Schramm, D. N; Bhattacharjee, P (American Association for the Advancement of Science, 1995-12)
    Recent experimental data seem to indicate that there is significant structure in the cosmic ray spectrum above 1018 electron volts (eV). Besides a dip at ~5 x 1018 eV, two events above 2 x 1020 eV have been observed. The ...
  • Injection spectrum of ultrahigh energy cosmic rays in the top-down scenario 
    Basu, R; Bhattacharjee, P (The American Physical Society, 2004-07)
    We analyze the uncertainties involved in obtaining the injection spectra of UHECR particles in the top-down scenario of their origin. We show that the Dokshizer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) Q/Sup2 evolution of ...
  • Long-term study of Mkn 421 with the HAGAR array of telescopes 
    Sinha, A; Shukla, A; Saha, L; Acharya, B. S; Anupama, G. C; Bhattacharjee, P; Britto, R. J; Chitnis, V. R; Prabhu, T. P; Singh, B. B; Vishwanath, P. R (EDP Sciences, 2016-07)
    Context. The HAGAR Telescope Array at Hanle, Ladakh has been regularly monitoring the nearby blazar Mkn 421 for the past seven years. Aims. Blazars show flux variability in all timescales across the electromagnetic ...
  • Monopole annihilation and highest energy cosmic rays 
    Bhattacharjee, P; Sigl, G (The American Physical Society, 1995-04)
    Cosmic rays with energies exceeding 1020 eV have been detected. The origin of these highest energy cosmic rays remains unknown. Established astrophysical acceleration mechanisms encounter severe difficulties in accelerating ...
  • Multi-frequency, multi-epoch study of MrK 501: hints for a two-component nature of the emission 
    Shukla, A; Chitnis, V. R; Singh, B. B; Acharya, B. S; Anupama, G. C; Bhattacharjee, P; Britto, R. J; Mannheim, K; Prabhu, T. P; Saha, L; Vishwanath, P. R (IOP Publishing, 2015-01-01)
    Since the detection of very high energy (VHE) γ -rays from Mrk 501, its broadband emission of radiation was mostly and quite effectively modeled using the one zone emission scenario. However, broadband spectral and flux ...
  • Multiwavelength analysis of low surface brightness galaxies to study possible dark matter signature 
    Bhattacharjee, P; Majumdar, P; Mousumi Das; Das, Subinoy; Joarder, P. S; Biswas, Sayan (Oxford University Press on behalf of the Royal Astronomical Society, 2021-03)
    Low surface brightness (LSB) galaxies have very diffuse, low surface density stellar discs that appear faint in optical images. They are very rich in neutral hydrogen (H I) gas, which extends well beyond the stellar discs. ...
  • Multiwavelength study of the TeV blazar Mrk 421 during a giant flare 
    Shukla, A; Chitnis, V. R; Vishwanath, P. R; Acharya, B. S; Anupama, G. C; Bhattacharjee, P; Britto, R. J; Prabhu, T. P; Saha, L; Singh, B. B (EDP Sciences, 2012-05)
    Aims. The nearby (z = 0.031) TeV blazar Mrk 421 was reported to be in a high state of flux activity since November, 2009. We aim to investigate possible changes in the physical parameters of Mrk 421 during its high state ...
  • Observations with the High Altitude GAmma Ray (HAGAR) telescope array in the Indian Himalayas 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhatt, N; Bhattacharjee, P; Bhattacharya, S. S; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Koul, R; Mahesh, P. K; Mitra, A; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; Rannot, R. C; Rao, S. K; Saha, L; Saleem, F; Saxena, A. K; Sharma, S. K; Shukla, A; Singh, B. B; Srinivasan, R; Srinivasulu, G; Sudersanan, P. V; Tickoo, A. K; Tsewang, D; Upadhya, S; Vishwanath, P. R; Yadav, K. K (French Society of Astronomy and Astrophysics, 2010-12)
    For several decades, it was thought that astrophysical sources emit high energy photons within the energy range of the gamma-ray region of the lectromagnetic spectrum also. These photons originate from interactions of high ...
  • Observations with the High Altitude GAmma-Ray (HAGAR) telescope array in the Indian Himalayas 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhatt, N; Bhattacharjee, P; Bhattacharya, S; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Koul, R; Manoharan, J; Mahesh, P. K; Mitra, A; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; Rannot, R. C; Rao, S. K; Saha, L; Saleem, F; Saxena, A. K; Sharma, S. K; Shukla, A; Singh, B. B; Srinivasan, R; Srinivasulu, G; Sudersanan, P. V; Tickoo, A. K; Tsewang, D; Upadhya, S. S; Vishwanath, P. R; Yadav, K. K (Copernicus Publications, 2011-11)
    The High Altitude GAmma-Ray (HAGAR) array is a wavefront sampling array of 7 telescopes, set-up at Hanle, at 4270 m amsl, in the Ladakh region of the Himalayas (Northern India). It constitutes the first phase of the HImalayan ...
  • On the origin of highest energy cosmic rays 
    Sigl, G; Schramm, D. N; Bhattacharjee, P (Elsevier, 1994-09)
    In this paper we show that the conventional diffusive shock acceleration mechanism for cosmic rays associated with relativistic astrophysical shocks in active galactic nuclei (AGNs) has severe difficulties to explain the ...
  • On the survivability of cosmological quark nuggets 
    Bhattacharjee, P (World Scientific, 1994)
    The question of survivability of quark nuggets against the process of baryon evaporation from their surfaces is discussed within the context of a dynamical model, namely, the chromoelectric flux-tube fission model of baryan ...
  • Origin and propagation of extremely high-energy cosmic rays 
    Bhattacharjee, P; Sigl, G. G (Elsevier, 2000-04)
    Cosmic ray particles with energies in excess of 10**20 eV have been detected. The sources as well as the physical mechanism(s) responsible for endowing cosmic ray particles with such enormous energies are unknown. This ...
  • Origin of the highest energy cosmic rays 
    Bhattacharjee, P (Indian Academy of Sciences, 1996-10)
    After briefly recalling the history of discovery of cosmic rays, the present statns of the subject is discussed. Cosmic-ray particles with energy exceeding 1020 eV have been detected. The origin of cosmic rays remains ...
  • Probing grand unified theories with cosmic-ray, gamma-ray, and neutrino astrophysics 
    Sigl, G; Lee, S; Bhattacharjee, P; Yoshida, S (The American astronomical Society, 1999-04)
    We explore scenarios where the highest energy cosmic rays are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic nucleon, γ-ray, and neutrino propagation, ...

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