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Browsing by Author "Sagar, R"

Browsing by Author "Sagar, R"

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  • 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 ...
  • Effect of mass segregation on mass function of young open clusters 
    Pandey, A. K; Mahra, H. S; Sagar, R (Astronomical Society of India, 1992)
    The effect of mass segregation on cluster mass function has been studied and it is found that the slope of the mass function is steeper in the outer part of the open clusters. Since derived dynamical relaxation time is ...
  • Emission from GRBs and their afterglows : Indian observations 
    Sagar, R (Astronomical Society of India, 2001)
    The study of Gamma-ray bursts, electromagnetically the most luminous events in the Universe though only for a few seconds, was revolutionized in 1997 when the Italian-Dutch X-ray satellite BeppoSAX started providing the ...
  • Emission-line CCD imaging of three southern symbiotic stars 
    Bhatt, H. C; Sagar, R (Indian Academy of Sciences, 1991-06)
    Symbiotic stars that are strong radio sources and have cool dust emitting in the IR are expected to have extended emission nebulae around them. In order to search for such emission nebulae, CCD imaging of three symbiotic ...
  • Estimation of the size and structure of the broad line region using Bayesian approach 
    Mandal, A. K; Rakshit, S; Stalin, C. S; Petrov, R. G; Mathew, B; Sagar, R (Oxford University Press on behalf of the Royal Astronomical Society, 2021-04)
    Understanding the geometry and kinematics of the broad line region (BLR) of active galactic nuclei (AGN) is important to estimate black hole masses in AGN and study the accretion process. The technique of reverberation ...
  • Evaluation of fractional clear sky over potential astronomical sites 
    Shantikumar, N. S; Song, H.- J; Mugil, S. K; Dumka, U. C; Larson, E. J. L; Brijesh Kumar; Sagar, R (Oxford University Press on behalf of Royal Astronomical Society, 2021-11)
    The estimation of the night-time cloud fraction (CF) is found to be one of the key parameters for evaluating the number of useful nights at an astronomical site. This work evaluates useful astronomical night-time observation ...
  • Evidence for Low-power Radio Jet–ISM Interaction at 10 pc in the Dwarf AGN Host NGC 4395 
    Nandi, Payel; Stalin, C. S; Saikia, D. J; Riffel, Rogemar A; Manna, Arijit; Pal, Sabyasachi; Dors, O. L; Wylezalek, Dominika; Paliya, Vaidehi S; Saikia, Payaswini; Dabhade, Pratik; Patig, Markus-Kissler; Sagar, R (American Astronomical Society, 2023-12-20)
    Black-hole-driven outflows in galaxies hosting active galactic nuclei (AGN) may interact with their interstellar medium (ISM) affecting star formation (SF). Such feedback processes, reminiscent of those seen in ...
  • Evolution of the Type IIb SN 2011fu 
    Pandey, S. B; Kumar, B; Sahu, D. K; Vinko, J; Moskvitin, A. S; Anupama, G. C; Bhatt, V. K; Ordasi, A; Nagy, A; Sokolov, V. V; Sokolova, T. N; Komarova, V. N; Kumar, B; Bose, S; Roy, R; Sagar, R (Cambridge University Press, 2014-01)
    The UBVRI photometric follow-up of SN 2011fu has been initiated a few days after the explosion, shows a rise followed by steep decay in all bands and shares properties very similar to that seen in case of SN 1993J, with a ...
  • Fibre spectroscopy and BV CCD photometry of the southern open cluster NGC 3114 
    Sagar, R; Sharples, Ray M (European Southern Observatory, 1991-04)
    New spectroscopic and photometric observations are presented for a sample of faint stars which extends the color-magnitude diagram of the open cluster NGC 3114 down to V = 16 mag. The distance to the cluster is estimated ...
  • Field star contamination in open star cluster NGC 2301 
    Mohan, V; Sagar, R (Astronomical Society of Indian, 1988-12)
    Photographic photometry of about 900 stars down to V = 17 mag has been carried out in the region of the open cluster NGC 2301. The cluster region seems to be severely contaminated by field stars. Statistical criteria yield ...
  • First Results from Light Scattering Enhancement Factor over Central Indian Himalayas during GVAX Campaign 
    Dumka, U. C; Kaskaoutis, D. G; Sagar, R; Chen, J; Singh, N; Tiwari, S (Elsevier B.V, 2017-02)
    The present work examines the influence of relative humidity (RH), physical and optical aerosol properties on the light-scattering enhancement factor [f(RH=85%)] over central Indian Himalayas during the Ganges Valley ...
  • 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)
  • Further evidence for intra-night optical variability of radio-quiet quasars 
    Goyal, Arti; Gopal-Krishna; Sagar, R; Anupama, G. C; Sahu, D. K (Astronomical Society of India, 2007-06)
    Although well established for BL Lac objects and radio-loud quasars, the occurrence of intra-night optical variability (INOV) in radio-quiet quasars is still debated, primarily since only a handful of INOV events with good ...
  • The Gap in the H-R Diagram of Open Clusters with Special Reference to NGC 2169, NGC 1778 and Tr I 
    Sagar, R; Joshi, U. C (Astronomical Society of India, 1978-06)
    The colour-magnitude diagrams of the open clusters NGC 1778 and Tr I indicate the presence of gaps on the rising branches of the evolving main sequnces. The positions of these gaps are compared with those found in other ...
  • The giant branch of the Fornax dwarf spheroidal galaxy 
    Sagar, R; Hawkins, M. R. S; Cannon, R. D (The Royal Astronomical Society, 1990-01)
    A color-magnitude diagram for a large sample of stars in the Fornax dwarf spheroidal galaxy has been obtained from BV electronographic observations. These reach to the level of the horizontal branch, below V = 21 mag. The ...
  • A Global Prospective of the Indian Optical and Near-Infrared Observational Facilities in the Field of Astronomy and Astrophysics: A Review 
    Sagar, R (Springer India, 2017-03)
    A review of modernization and growth of ground based optical and near-infrared astrophysical observational facilities in the globe attributed to the recent technological developments in opto-mechanical, electronics and ...
  • Globular cluster systems in giant elliptical galaxies : a probe for the galaxy formation and evolution 
    Subramaniam, A; Sagar, R (Astronomical Society of India, 2000)
    Most of the globular clusters in the universe reside in gaint elliptical galaxies. The number of GCs present in them is about a few thousands. Due to their large distances (> 10 Mpc), it is impossible to observe their ...
  • GRB 000301C with peculiar afterglow emission 
    Sagar, R; Mohan, V; Pandey, S. B; Pandey, A. K; Stalin, C. S; Castro-Tirado, A. J (Astronomical Society of India, 2000)
    The CCD magnitudes in Johnson V and Cousins R and I photometric passbands are determined for GRB 000301C afterglow starting ~ 1.5 day after the γ - ray burst. In fact we provide the earliest optical observations for this ...
  • 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 ...

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