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Browsing by Author "Sagar, R"

Browsing by Author "Sagar, R"

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  • 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 ...
  • Light curve and spectral evolution of the Type IIb supernova 2011fu 
    Kumar, Brajesh; Pandey, S. 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, Brijesh; Bose, S; Roy, R; Sagar, R (Oxford University Press on behalf of the Royal Astronomical Society, 2013-05-01)
    We present the low-resolution spectroscopic and UBVRI broad-band photometric investigations of the Type IIb supernova (SN) 2011fu, discovered in UGC 01626. The photometric follow-up of this event was initiated a few days ...
  • The Mass Function of Young Star Clusters in our Galaxy and Nearby Galaxies: Is It Universal? 
    Sagar, R (International Astronomical union, 2002)
    Mass functions (MFs) derived from photometric observations of young star clusters of our Galaxy, the Magellanic Clouds (MCs), M31 and M33 have been used to investigate the question of universality of the initial mass ...
  • Measurements of linear polarization of some Herbig Ae/Be stars 
    Jain, S. K; Bhatt, H. C; Sagar, R (The American Physical Society, 1990-05)
    The linear polarization of eight bright Herbig Ae/Be stars in UBVRI bands has been measured. No unique wavelength dependence of polarization magnitude or direction is found in these measurements. Comparison with earlier ...
  • Multi-colour optical monitoring of the intra-day variable blazar S5 0716+71 
    Sagar, R; Gopal-Krishna; Mohan, V; Pandey, A. K; Bhatt, B. C; Wagner, S. J (The European Southern Observatory, 1999-02)
    We report multi-colour optical monitoring of the intra-day variable blazar S5 0716+71 with a dense temporal coverage over a total duration of 4 weeks in February/March 1994. Four filters (BV Johnson and RI Cousins) were ...
  • Multicolor CCD Photometry and Stellar Evolutionary Analysis of NGC 1907, NGC 1912, NGC 2383, NGC 2384, and NGC 6709 Using Synthetic Color-Magnitude Diagrams 
    Subramaniam, A; Sagar, R (The American Astronomical Society, 1999-02)
    We present the first CCD photometric observations of NGC 2383 and NGC 2384 in B, V, R, and I, NGC 1912, NGC 6709 in B, V, and I and NGC 1907 in B and V passbands, reaching down to a limiting magnitude of V~20 mag for ~3300 ...
  • A multicolour CCD photometric and mass function study of the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253 
    Sagar, R; Munari, U; de Boer, K. S (Royal Astronomical Society, 2001-10)
    We derive cluster parameters and mass functions from new UBVRI CCD photometric observations of ~3500 stars reaching down to V~20mag for the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC ...

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