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Browsing by Author "Sagar, R"

Browsing by Author "Sagar, R"

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  • 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 ...
  • HD 12098 a new far-northern roAp star 
    Girish, V; Joshi, S; Seetha, S; Ashoka, B. N; Martinez, P; Chaubey, U. S; Gupta, S. K; Kurtz, D. W; Sagar, R (Astronomical Society of India, 2001)
    The rapidly oscillating Ap (roAp) stars are cool, magnetic, chemically peculiar stars which pulsate in non-radial p-modes in the period range 4-16 min and have Johnson B amplitudes less than 8 mmag. "The NainiTal-Cape ...
  • 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 ...
  • Influence of a third body on the luminosity of a contact binary system 
    Barman, S. K; Sagar, R (Astronomical Society of India, 1996)
  • 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. ...
  • Integrated photometric parameters of open and globuler clusters 
    Sagar, R; Joshi, U. C; Sinvhal, S. D (Astronomical Society of India, 1983-03)
    In this work we have discussed UBV parameters of 142 galactic clustes and 32 globular clusters. Comparison of the integrated parameters of galactic clusters with the theoretical ones confirms the validity of the basic ...
  • 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 ...
  • Internal motions in the open star clusters NGC 654 and 6087 
    Sagar, R; Bhatt, H. C (Astronomical Society of Indian, 1989-03)
    Proper motion measurements are used to study the internal kinematics in the open star clusters NGC 654 and 6087. It is found that intrinsic dispersions are independent of stellar mass and radial distance in both clusters. ...
  • 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. ...
  • Intracluster extinction in young open star clusters 
    Sagar, R; Qian, Z. Y (Astronomical Society of India, 1993)
    An analysis of near-infrared data in combination with optical observations, indicates a normal interstellar extinction law around hot O and B stars at wavelengths greater than or = 0.9 micrometers. At shorter wavelengths, ...
  • 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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