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Browsing by Author "Bhattacharya, D"

Browsing by Author "Bhattacharya, D"

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  • Comprehensive multiwavelength modelling of the afterglow of GRB 050525A 
    Resmi, L; Misra, K; Johannesson, G; Castro-Tirado, A. J; Gorosabel, J; Jelınek, M; Bhattacharya, D; Kubanek, P; Anupama, G. C; Sota, A; Sahu, D. K; de Ugarte Postigo, A; Pandey, S. B; Sanchez-Ramırez, R; Bremer, M; Sagar, R (Wiley-Blackwell, 2012-11)
    The Swift era has posed a challenge to the standard blast-wave model of gamma-ray burst (GRB) afterglows. The key observational features expected within the model are rarely observed, such as the achromatic steepening ...
  • The dark nature of GRB 051022 and its host galaxy 
    Castro-Tirado, A. J; Bremer, M; McBreen, S; Gorosabel, J; Guziy, S; Fakthullin, T. A; Sokolov, V. V; González Delgado, R. M; Bihain, G; Pandey, S. B; Jelínek, M; de Ugarte Postigo, A; Misra, K; Sagar, R; Bama, P; Kamble, A. P; Anupama, G. C; Licandro, J; Pérez-Ramírez, D; Bhattacharya, D; Aceituno, F. J; Neri, R (EDP Sciences, 2007-11)
    Aims.We present multiwavelength (X-ray/optical/near-infrared/millimetre) observations of GRB 051022 between 2.5 h and ~1.15 yr after the event. It is the most intense gamma-ray burst (~10-4 erg cm-2) detected by HETE-2, ...
  • Does black hole spin play a key role in the FSRQ/BL Lac dichotomy? 
    Bhattacharya, D; Sreekumar, P; Mukhopadhyay, B; Tomar, I (IOP Publishing, 2016-04)
    Blazars are characterized by large intensity and spectral v ariations across the electromagnetic spectrum It is believed that jets emerging from them are almo st aligned with the line-of-sight. The major- ity of ...
  • A Dynamic Sky Simulation for the Scanning Sky Monitor on ASTROSAT 
    Mishra, S. D; Bhattacharya, D (Astronomical Society of India, 2003)
    We have developed a dynamic sky simulation software for the visualization of the operation of the Scanning Sky Monitor cameras. This software can be used for the background modelling of the cameras and the refinement of ...
  • Early optical and millimeter observations of GRB 030226 afterglow 
    Pandey, S. B; Sagar, R; Anupama, G. C; Bhattacharya, D; Sahu, D. K; Castro-Tirado, A. J; Bremer, M (EDP Sciences, 2004-04)
    The CCD magnitudes in Johnson UBV and Cousins RI photometric passbands for the afterglow of the long duration GRB 030226 are presented. Upper limits of a few mJy to millimeter wave emission at the location of optical are ...
  • Energy and Radiation Spectrum of Electrons in Ultra-relativistic Shocks of GRB Afterglows 
    Resmi, L; Bhattacharya, D (Astronomical Society of India, 2003)
    We consider particle acceleration near ultra relativistic shocks (shock p 1) and the distribution of accelerated particles in the shock downstream. We suggest that the electron energy spectrum will settle mp into an ...
  • Flat Spectrum Gamma Ray Burst Afterglows 
    Bhattacharya, D (Astronomical Society of India, 2001)
    Temporal behaviour of GRB afterglow light curve is derived for the case where the electron energy distribution is relatively hard, with the power-law index p lying between 1.0 and 2.0. It is shown that the expected behaviour ...
  • A flattening in the optical light curve of SN 2002ap 
    Pandey, S. B; Anupama, G. C; Sagar, R; Bhattacharya, D; Sahu, D. K; Pandey, J. C (Royal Astronomical Society, 2003-04)
    We present the UBVRcIc broad-band optical photometry of the Type Ic supernova SN 2002ap obtained during 2002 February 6-March 23 in the early decline phases and also later on 2002 August 15. Combining these data with the ...
  • A Flattening in the Optical Light Curve of SN 2002ap. 
    Pandey, S. B; Anupama, G. C; Sagar, R; Bhattacharya, D; Sahu, D. K; Pandey, J. C (Blackwell Publishing, Edinburge, UK, 1994)
  • General relativistic spectra of accretion discs around rapidly rotating neutron stars: effect of light bending 
    Bhattacharyya, S; Bhattacharya, D; Thampan, A. V (Royal Astronomical Society, 2001-08)
    We present computed spectra, as seen by a distant observer, from the accretion disc around a rapidly rotating neutron star. Our calculations are carried out in a fully general relativistic framework, with an exact treatment ...
  • GRB 000926 and its optical afterglow : Another possible evidence for non-isotropic emission 
    Sagar, R; Pandey, S. B; Mohan, V; Bhattacharya, D; Castro-Tirado, A. J (Astronomical Society of India, 2001)
    The CCD Johnson BV and Cousins RI photomertric magnitudes are determined for 20 stars in the field of GRB 000926. They are used to calibrate the present R as well as published BVRI photometric magnitudes of the GRB 000926 ...
  • Image Reconstruction for a Continuously Rotating Coded Mask Camera 
    Shankar, B. T. R; Bhattacharya, D (Astronomical Society of India, 2003)
    We discuss a method for reconstructing the image for Scanning Sky Monitor which is a continuously rotating X-ray coded mask camera aboard the Indian astronomical satellite, ASTROSAT.
  • Imaging with the Scanning Sky Monitor on ASTROSAT 
    Bhattacharya, D; Shankar, B. T. R (Astronomical Society of India, 2002-09)
    This paper describes the status of the development of software for coded mask imaging with the Scanning Sky Monitor aboard the proposed Indian multi wavelength astronomy satellite ASTROSAT.
  • Implications of kHz quasi-periodic brightness oscillations in X-ray binaries for neutron star structure 
    Thampan, A. V; Bhattacharya, D; Datta, B (Blackwell Science Ltd., 1999-02)
    Kilohertz quasi-periodic oscillations (QPOs) in low-mass X-ray binaries (LMXBs) may represent the orbital frequencies of the innermost Keplerian orbits around accreting neutron stars. Attempts have recently been made to ...
  • 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 ...
  • Neutron star physics in the square kilometre array era: an Indian perspective 
    Konar, S; Bagchi, Manjari; Bandyopadhyay, Debades; Banik, Sarmistha; Bhattacharya, D; Bhattacharyya, S; Gangadhara, R. T; Gopakumar, A; Gupta, Y; Joshi, B. C; Maan, Yogesh; Maitra, Chandreyee; Mukherjee, D; Pai, Archana; Paul, B; Ray, A; Sutaria, F. K (Indian Academy of Sciences, 2016-12)
    It is an exceptionally opportune time for astrophysics when a number of next-generation mega-instruments are poised to observe the Universe across the entire electromagnetic spectrum with unprecedented data quality. The ...
  • A Numerical Survey of Neutron Star Crustal Density Profiles 
    Datta, B; Thampan, A. V; Bhattacharya, D (Indian Academy of Sciences, 1995-12)
    An accurate numerical survey of the density profiles corresponding to the crusts of neutron stars for representative equation of state models is presented. This will find application in calculations of thermal and magnetic ...
  • Ohmic decay of magnetic flux expelled from neutron star interiors 
    Bhattacharya, D; Datta, B (Royal Astronomical Society, 1996-10)
    We study Ohmic diffusion of magnetic flux expelled from the superconducting core of a neutron star to its crust owing to spindown-induced field evolution. We find that Ohmic decay time-scales in the range 10^7.5-10^9 yr ...
  • The optical afterglow of the not so dark GRB 021211 
    Pandey, S. B; Anupama, G. C; Sagar, R; Bhattacharya, D; Castro-Tirado, A. J; Sahu, D. K; Parihar, P. S; Prabhu, T. P (The European Southern Observatory, 2003-09)
    We determine Johnson B,V and Cousins R,I photometric CCD magnitudes for the afterglow of GRB 021211 during the first night after the GRB trigger. The afterglow was very faint and would have been probably missed if no prompt ...
  • 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 ...

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