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Browsing by Author "Sagar, R"

Browsing by Author "Sagar, R"

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  • A comprehensive study of the rich open star cluster NGC 2099 based on deep BVI CCD observations 
    Nilakshi; Sagar, R (E D P Sciences, 2002-01)
    The CCD observations of the rich open star cluster NGC 2099 and its surrounding field region have been carried out up to a limiting magnitude of V ~ 22 mag in B, V and I passbands for the first time. A total of ~ 12 000 ...
  • 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, ...
  • A deep BVI photometric study of the open cluster NGC 2453 
    Mallik, D. C. V; Sagar, R; Pati, A. K (EDP Sciences, 1995-12)
    CCD observations of the open cluster NGC 2453 have been carried out in B, V and I passbands. A total of 356 stars have been observed in a field of about 4'x6' of the sky centred on the cluster. Colour-magnitude diagrams ...
  • A deep UBVRI CCD photometric study of the moderately young southern open star cluster NGC 4755 = Kappa-Crucis 
    Sagar, R; Cannon, R. D (The European Southern Observatory, 1995-05)
    CCD observations in U, B, V, R and I passbands have been used to generate (U-B), (B-V) colour-colour and deep V, (B-V); V, (U-B) and V, (V-I) colour-magnitude diagrams for the young open cluster NGC 4755. The sample consists ...
  • A deep UBVRI CCD photometric study of the open clusters Tr1 and Be 11 
    Yadav, R. K. S; Sagar, R (Royal Astronomical Society, 2002-11)
    We present deep UBVRI charge-coupled device (CCD) photometry for the young open star clusters Tr1 and Be11. The CCD data for Be11 are obtained for the first time. The sample consists of ~1500 stars reaching down to V~ 21 ...
  • A deep V I CCD photometric study of the neglected galactic star cluster NGC 6631 
    Sagar, R; Naidu, B. N; Mohan, V (Astronomical Society of India, 2001)
    We present the V I CCD photometric observations of about 5500 stars up to a limiting magnitude of V ~ 20 in an area of ~ 16? x 16? around the cluster NGC 6631. The cluster parameters determined for the first time by fitting ...
  • Determination of the size of the dust torus in H0507+164 through optical and infrared monitoring 
    Amit Kumar; Rakshit, S; Kshama, S. K; Stalin, C. S; Mathew, B; Hoenig, Sebastian; Gandhi, Poshak; Sagar, R; Pandge, M. B (Oxford University Press on behalf of the Royal Astronomical Society, 2018-04)
    The time delay between flux variations in different wavelength bands can be used to probe the inner regions of active galactic nuclei (AGNs). Here, we present the first measurements of the time delay between optical and ...
  • Discovery of a planetary system around 51 Pegasus 
    Sagar, R (Astronomical Society of India, 1996)
  • Discovery of pulsations in HD 98851 
    Joshi, S; Girish, V; Martinez, P; Sagar, R; Ashoka, B. N; Gupta, S. K; Seetha, S; Chaubey, U. S; Kurtz, D. W (Astronomical Society of India, 2001)
    Using the UPSO 1-m Sampurnanand reflector telescope equipped with a fast photometer, we observed the chemically peculiar (CP) star HD 98851 for a total of around 30 hours on 5 different nights between January to April 2000. ...
  • Distribution of stellar mass in young star clusters of our Galaxy and nearby galaxies 
    Sagar, R (Astronomical Society of India, 2000)
    Stellar mass distribution in young star clusters of our Galaxy, the Magellanic Clouds and the nearby local groups of galaxies has been used to investigate the universality of initial mass function and presence of mass ...
  • Dust reverberation mapping of Z229–15 
    Mandal, A. K; Rakshit, S; Stalin, C. S; Wylezalek, D; Patig, M. K; Sagar, R; Mathew, B; Muneer, S; Pal, I (Oxford University Press on behalf of the Royal Astronomical Society, 2021-03)
    We report results of the dust reverberation mapping (DRM) on the Seyfert 1 galaxy Z229–15 at z = 0.0273. Quasi-simultaneous photometric observations for a total of 48 epochs were acquired during the period 2017 July to ...
  • 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 ...

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