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Browsing by Author "Sagar, R"

Browsing by Author "Sagar, R"

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  • Binary star clusters in galaxies : Our galaxy 
    Subramaniam, A; Gorti, U; Sagar, R; Bhatt, H. C (Astronomical Society of India, 2000)
  • BVRI CCD photometric standards in the field of GRB 990123 
    Nilakshi; Yadav, R. K. S; Mohan, V; Pandey, A. K; Sagar, R (Astronomical Society of India, 1999)
    The CCD magnitudes in Johnson BV and Cousins RI photometric passbands are determined for 18 stars in the field of GRB 990123. These mesurements can be used in carrying out precise CCD photometry of the optical transient ...
  • CCD imaging of gamma ray burster fields 
    Bhargavi, S. G; Cowsik, R; Pati, A. K; Sagar, R (Astronomical Society of India, 1998)
  • CCD photometry in VRI bands of the galactic cluster NGC 2818 
    Surendiranath, R; Kameswara Rao, N; Sagar, R; Nathan, J. S; Ghosh, K. K (Indian Academy of Sciences, 1990-06)
    The open cluster NGC 2818 containing a planetary nebula has been observed in VRI bands using the CCD system at prime focus of the 2.3 meter Vainu Bappu Telescope. The study extending to stars V of 21 magnitude established ...
  • CCD Photometry of NGC 2453 
    Mallik, D. C. V; Sagar, R; Pati, A. K (International Astronomical Union, 1993)
  • CCD photometry of the distant southern globular cluster NGC 5824 
    Cannon, R. D; Sagar, R; Hawkins, M. R. S (Royal Astronomical Society, 1990-03)
    A V, (B-V) C-M diagram for the distant globular cluster NGC 5824 is obtained from CCD observations of 285 stars reaching V = 20.5. Assuming a reddening of E(B-V) = 0.13, the color of the giant branch at the level of the ...
  • CCD photometry of the distant young open cluster NGC 7510 
    Sagar, R; Griffiths, W. K (Royal Astronomical Society, 1991-06)
    CCD observations in B, V, and I passbands have been used to generate deep V, (B-V), and V,(V-I) color-magnitude diagrams for the open cluster NGC 7510. The sample consists of 592 stars reaching down to V = 21 mag. There ...
  • CCD photometry of the galactic open star clusters. I - King 10 
    Mohan, V; Pandey, A. K; Paliwal, D. C; Sagar, R; Mahra, H. S (Astronomical Society of India, 1992)
    CCD photometry of the open cluster King 10 has been carried out in the UBVRI photometric passbands down to V of about 19.5 mag. The reddening for the cluster region is found to be variable. A distance of 3.2 kpc has been ...
  • CCD photometry of the galactic star clusters Be 15, Be 71 and King 1 
    Lata, S; Mohan, V; Sagar, R (Astronomical Society of India, 2004-12)
    We present UBV RI CCD photometry of three open star clusters Be 15, Be 71 and King 1 for the fist time. Base on these data, optical colour magnitude diagrams (CMDs) for the stars in the clusters down to V = 22 mag are ...
  • CCD photometry of the unstudied galactic star clusters Be 10, Be 67 and To 5 
    Lata, S; Mohan, V; Pandey, A. K; Sagar, R (Astronomical Society of India, 2004-03)
    We present the broad band Johnson U BV and Cousins RI CCD photometric observations for open clusters Be 10, Be 67 and To 5. So far no photometric study of these clusters is published. The colour-magnitude diagrams indicate ...
  • Changing look AGN Mrk 590: broad-line region and black hole mass from photometric reverberation mapping 
    Amit Kumar Mandal; Schramm, Malte; Rakshit, Suvendu; Stalin, C. S; Vijarnwannaluk, Bovornpratch; Rujopakarn, Wiphu; Poshyachinda, Saran; Kouprianov, Vladimir V; Haislip, Joshua B; Reichar, Daniel E; Sagar, R; Mathew, Blesson (Oxford University Press on behalf of Royal Astronomical Society, 2021-12)
    We present the results of photometric reverberation mapping observations on the changing look active galactic nucleus Mrk 590 at z = 0.026. The observations were carried out from 2018 July to December using broad-band B-, ...
  • A comparative study of the intra-night optical variability of powerful AGNs 
    Stalin, C. S; Gopal-Krishna; Sagar, R; Wiita, P. J (Astronomical Society of India, 2002-09)
    In order to address a currently much debated issue, we are carrying out a systematic search for intra-night optical micro-variability in major classes of powerful (M'II ~ -23.0 mag) active galactic nuclei (AGNs). Our ...
  • A complete photometric study of the open cluster NGC 7790 containing Cepheid variables 
    Gupta, A. C; Subramaniam, A; Sagar, R; Griffiths, W. K (EDP Sciences, 2000-09)
    CCD photometry of the northern open star cluster NGC 7790 has been carried out in BVI photometric passbands down to V ~ 21 mag for 1150 stars of which for ~ 700 stars, the data is obtained for the first time. We derive the ...
  • 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 ...
  • 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 ...

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