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Browsing by Author "Sagar, R"

Browsing by Author "Sagar, R"

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  • Study of interstellar extinction in some young open clusters 
    Sagar, R (Royal Astronomical Society, 1987-09)
    Interstellar extinction has been studied in 15 open clusters, based on reliable cluster members and precise observational data. Out of these, 10 show nonuniform extinction across the cluster region. Most of these show ...
  • A study of spatial structure of galactic open star clusters 
    Nilakshi; Sagar, R; Pandey, A. K; Mohan, V (E D P Sciences, 2002-02)
    In order to study the relation between the core and corona in galactic star clusters, the spatial structure of 38 rich open star clusters has been studied using radial density profiles derived from the photometric data of ...
  • Study of the Galactic Cluster NGC 581 
    Sagar, R; Joshi, U. C (Astronomical Society of India, 1978-03)
    Photoelectric magnitudes and colours in the UBV system have been determined for 73 stars in NGC 581. The value of the interstellar reddening is 0m.38. The distance modules to the cluster is estimated at 12m.16 plus or ...
  • A study of the old galactic star cluster Berkeley 32 
    Richtler, T; Sagar, R (Astronomical Society of India, 2001)
    We present new CCD photometry of the distant old open star cluster Berkeley 32 in Johnson V and Cousins I passbands. A total of ~ 3200 stars have been observed in a field of about 13? x 13?. The colour-magnitude diagram ...
  • A study of the spatial stellar mass distribution in some young open clusters 
    Sagar, R; Miakutin, V. I; Piskunov, A. E; Dluzhnevskaia, O. B (Royal Astronomical Society, 1988-10)
    The stellar spatial distribution is studied as a function of mass in 11 young open clusters. In seven of these clusters, mass segregation is observed. The possibility of two cluster centers for NGC 2264 is discussed. It ...
  • A study of the spatial variation of mass functions in some young open clusters 
    Pandey, A. K; Mahra, H. S; Sagar, R (Astronomical Society of the Pacific, 1991)
    The effect of mass segregation on cluster mass functions has been studied and it is found that the slope of the mass function is steeper in the outer parts of open dusters. Since dynamical relaxation time is always larger ...
  • Supernova 2012aw – a high-energy clone of archetypal Type IIP SN 1999em 
    Bose, Subhash; Kumar, Brijesh; Sutaria, F. K; Kumar, Brajesh; Roy, Rupak; Bhatt, V. K; Pandey, S. B; Chandola, H. C; Sagar, R; Misra, Kuntal; Chakraborti, Sayan (Oxford University Press, 2013-08-11)
    We present densely sampled UBVRI/griz photometric and low-resolution (6–10 Å) optical spectroscopic observations from 4 to 270 d after explosion of a newly discovered Type II SN 2012aw in a nearby (∼9.9 Mpc) galaxy M95. ...
  • Survey for roAp stars in the northern sky from Naini Tal 
    Ashoka, B. N; Seetha, S; Raj, E; Chaubey, U. S; Gupta, S. K; Joshi, S; Martinez, P; Kurtz, D. W; Sagar, R; Kasturirangan, K (Astronomical Society of India, 2000)
    Of the 31 known rapidly oscillating Ap (roAp) stars, 28 are in the southern sky and majority of them were discovered at SAAO indicating that a systematic survey also is needed in the northern sky. Therefore, a project has ...
  • Temporal behaviour of emissions from gamma-ray bursts and optical/near-IR afterglows of GRB 991208 and GRB 991216 
    Sagar, R; Mohan, V; Pandey, A. K; Pandey, S. B; Castro-Tirado, A. J (Astronomical Society of India, 2000)
    The CCD magnitudes in Cousins R and I photometric passbands are determined for GRB 991216 and GRB 991208 afterglows respectively ~ 1 and ~ 3 day after trigger of the corresponding gamma-ray bursts. Light curves of the ...
  • Testing the mechanisms for optical micro-variability of powerful active galactic nuclei 
    Gopal-Krishna; Sagar, R; Wiita, P. J (Astronomical Society of India, 1993)
    We present the first results of a new type of observational program being carried out using the 2.34m Vainu Bappu Telescope at Kavalur. This program involves intra-night optical monitoring of radio quiet but optically ...
  • UBV photoelectric photometry of the open cluster NGC 2539 
    Joshi, U. C; Sagar, R (Astronomical Society of Indian, 1986-06)
    UBV photometric observations of 135 stars near NGC 2539, obtained using the 104-cm Sampurnanand reflector at Uttar Pradesh State Observatory during 1975-1978, are reported. The data are presented in tables and graphs and ...
  • UBVRI CCD photometry of the OB associations Bochum 1 and Bochum 6 
    Yadav, R. K. S; Sagar, R (Astronomical Society of India, 2003)
    We report the first deep $UBVRI$ CCD photometry of 2460 stars in the field of two poorly studied OB associations Bochum 1 and Bochum 6. We selected 15 and 14 probable members in Bochum 1 and Bochum 6 respectively using ...
  • UBVRI CCD photometry of the two southern galactic star clusters Berkeley 79 and Trumpler 11 
    Sagar, R; Cannon, R. D (Astronomical Society of India, 1994)
  • Unusual optical quiescence of the classical BL Lac object PKS 0735+178 on intranight time scale 
    Goyal, A; Gopal-Krishna; Anupama, G. C; Sahu, D. K; Sagar, R; Britzen, S; Karouzos, M; Aller, M. F; Aller, H. D (Wiley Blackwell, 2009-07)
    We present the result of our extensive intranight optical monitoring of the well known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of $R$-band monitoring for a minimum duration of ...
  • UOCS – III. UVIT catalogue of open clusters with machine learning-based membership using Gaia EDR3 astrometry 
    Jadhav, Vikrant K; Pennock, C. M; Subramaniam, A; Sagar, R; Prasanta Kumar Nayak (Oxford University Press on behalf of the Royal Astronomical Society, 2021-05)
    We present a study of six open clusters (Berkeley 67, King 2, NGC 2420, NGC 2477, NGC 2682, and NGC 6940), using the Ultra Violet Imaging Telescope (UVIT) aboard ASTROSAT and Gaia EDR3. We used combinations of astrometric, ...
  • UOCS. IV. discovery of diverse hot companions to blue stragglers in the old open cluster King 2 
    Jadhav, Vikrant V; Pandey, Sindhu; Subramaniam, A; Sagar, R (Indian Academy of Sciences, 2021-10)
    King 2, one of the oldest clusters in the Milky Way, with an age of ∼6 Gyr and distance of ∼5700 pc, has been observed with UVIT payload on the AstroSat. With membership information derived from Gaia EDR3, the cluster is ...
  • UOCS. XIII. Study of the Far-ultraviolet Bright Stars in the Open Cluster NGC 2420 Using AstroSat 
    Yadav, R. K. S; Dattatrey, Arvind K; Rangwal, Geeta; Subramaniam, A; Bisht, D; Sagar, R (American Astronomical Society, 2024-02-01)
    We present the study of four far-ultraviolet (FUV) bright stars in the field of the open cluster NGC 2420 using the Ultra Violet Imaging Telescope mounted on AstroSat. The three stars 525, 527, and 560 are members, while ...
  • UPSO three channel fast photometer 
    Gupta, S. K; Sagar, R; Joshi, S; Ashoka, B. N; Babu, V. C; Seetha, S; Girish, V (Astronomical Society of India, 2001)
    The design and performance of a modular portable three channel fast photometer is described. It can be disassembled as single individual channels such that the system can also be used as a single channel photometer. The ...
  • V, I CCD photometry of metal-rich bulge globular clusters: NGC 6553 
    Sagar, R; Subramaniam, A; Richtler, T; Grebel, E. K (The European Southern Observatory, 1999-03)
    We have carried out VI CCD photometry of about 40 000 stars down to V ~ 23 mag in an area of about 6' x 10' centered on the metal-rich Galactic bulge globular cluster NGC 6553 and an adjacent field region. Our photometry ...
  • VI CCD photometry of metal-rich globular clusters: NGC 6528 
    Richtler, T; Grebel, E. K; Subramaniam, A; Sagar, R (European Southern Observatory, 1998-01)
    We present CCD photometry in V and I for the metal-rich globular cluster NGC 6528. A comparison with previous photometry reveals discrepancies of the order 0.1 to 0.2 mag in V, emphasizing the need for independent photometry. ...

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