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Browsing IIAP Publications by Author "Sagar, R"

Browsing IIAP Publications by Author "Sagar, R"

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  • 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 ...
  • 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 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 ...
  • Improved characterization of intranight optical variability of prominent AGN classes 
    Goyal, A; Gopal-Krishna; Wiita, P. J; Stalin, C. S; Sagar, R (Oxford University Press on behalf of the Royal Astronomical Society, 2013-10-21)
    The incidence of intranight optical variability (INOV) is known to differ significantly among different classes of powerful active galactic nuclei (AGN). A number of statistical methods have been employed in the literature ...
  • Integrated parameters of open clusters 
    Pandey, A. K; Bhatt, B. C; Mahra, H. S; Sagar, R (Royal Astronomical Society, 1989-01)
    Integrated magnitudes and colors of population I synthetic clusters have been derived using theoretical evolutionary tracks and an age-dependednt initial mass function. A comparison of the theoretically obtained integrated ...
  • Integrated photometric characteristics of galactic open star clusters 
    Lata, S; Pandey, A. K; Sagar, R; Mohan, V (E D P Sciences, 2002-06)
    Integrated UBVRI photometric parameters of 140 galactic open clusters have been computed. Integrated I(V-R)0 and I(V-I)0 colours as well as integrated parameters for 71 star clusters have been obtained for the first time. ...
  • Internal kinematics of open star clusters 
    Sagar, R; Bhatt, H. C (Royal Astronomical Society, 1989-02)
    Proper motion measurements are employed to investigate the internal kinematics of eight open star clusters. In most of the clusters considered, no dependence of the intrinsic dispersion in proper motion on stellar mass and ...
  • Intra-night optical variability of core dominated radio quasars: the role of optical polarization 
    Goyal, A; Gopal-Krishna; Wiita, P. J; Anupama, G. C; Sahu, D. K; Sagar, R; Joshi, S (EDP Sciences, 2012-08)
    Context. Rapid variations in optical flux are seen in many quasars and all blazars. The amount of variability in different classes of active galactic nuclei has been studied extensively but many questions remain unanswered. ...
  • Intranight optical monitoring of optically selected bright quasars 
    Sagar, R; Gopal-Krishna; Wiita, P. J (Royal Astronomical Society, 1996-08)
    As part of an ongoing programme to search for intranight optical variations, we report results for six radio-quiet and one radio-moderate, but all optically bright and luminous, quasi-stellar objects (QSOs), using the ...
  • Intranight optical variability in optically selected QSOs 
    Gopal-Krishna; Sagar, R; Wiita, J. Paul (Blackwell Publishing, 1995-06)
    We report results from a continuing programme to search for intranight optical variability in one radio-moderate and six radio-quiet (but all optically bright and luminous) quasi-stellar objects, using the 2.34-m Vainu ...
  • JHK photometric study of the variable interstellar extinction in the direction of open star cluster NGC 654 
    Sagar, R; Yu, Q. Z (The Royal Astronomical Society, 1989-10)
    JHK magnitudes have been determined for 18 stars in the field of NGC 654. Study of the interstellar extinction law in the cluster direction indicates an anomalous distribution of interstellar grains causing more extinction ...
  • Kinematical distances to open star clusters 
    Sagar, R; Bhatt, H. C (Indian Academy Sciences, 1988-06)
    Kinematical distances are estimated for six open star clusters. They agree fairly well with the photometric distances. The kinematical distances cannot, at present, be estimated better than the photometric distances. When ...

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