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Browsing by Author "Sagar, R"

Browsing by Author "Sagar, R"

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  • Optical observations and multiband modelling of the afterglow of GRB041006 : Evidence of a hard electron energy spectrum 
    Misra, K; Resmi, L; Pandey, S. B; Bhattacharya, D; Sagar, R (Astronomical Society of India, 2005-12)
    We present the CCD Cousins R band photometric observations of the afterglow of GRB 041006. The multiband afterglow evolution is modelled using an underlying `hard' electron energy spectrum with a p1 ~ 1.3. The burst appears ...
  • Optical observations of GRB 060124 afterglow: a case for an injection break 
    Misra, K; Bhattacharya, D; Sahu, D. K; Sagar, R; Anupama, G. C; Castro-Tirado, A. J; Guziy, S. S; Bhatt, B. C (EDP Sciences, 2007-03)
    Aims.We present broad band optical afterglow observations of a long duration GRB 060124 using the 1.04-m Sampurnanand Telescope at ARIES, Nainital and the 2.01-m HCT at IAO, Hanle, including the earliest ground-based ...
  • Optical observations of GRB afterglows from India 
    Sagar, R; Misra, K (Astronomical Society of India, 2005-06)
    Optical observations of GRB afterglows provide information about GRB distances as well as their isotropic/non-isotropic nature of emission. More than 30 GRB fields have been probed by us during 1999 to 2003, out of which ...
  • Optical observations of star clusters NGC 1513 and NGC 4147; white dwarf WD 1145þ017 and K band imaging of star-forming region Sh 2-61 with the 3.6-m Devasthal optical telescope 
    Sagar, R; Yadav, R. K. S; Pandey, S. B; Sharma, Saurabh; Lata, Sneh; Joshi, Santosh (Indian Academy of Sciences, 2022-06)
    The UBVRI CCD photometric data of open star cluster NGC 1513 are obtained with the 3.6-m Indo-Belgian Devasthal optical telescope (DOT). Analyses of the GAIA EDR3 astrometric data have identified 106 possible cluster ...
  • Optical observations of the bright long duration peculiar GRB 021004 afterglow. 
    Pandey, S. B; Sahu, D. K; Resmi, L; Sagar, R; Anupama, G. C; Bhattacharya, D; Mohan, V; Prabhu, T. P; Bhatt, B. C; Pandey, J. C; Parihar, P. S; Castro-Tirado, A. J (Astronomical Society of India, 2003)
    The CCD magnitudes in Johnson B,V and Cousins R and I photometric passbands are determined for the bright long duration GRB 021004 afterglow from 2002 October 4 to 16 starting ~ 3 hours after the γ - ray burst. Light curves ...
  • Optical variability of radio-intermediate quasars 
    Goyal, Arti; Gopal-Krishna; Joshi, S; Sagar, R; Wiita, Paul J; Anupama, G. C; Sahu, D. K (Blackwell Publishing, 2010-02)
    We report the results of our intensive intranight optical monitoring of eight optically bright `radio-intermediate quasars' (RIQs) having flat or inverted radio spectra. The monitoring was carried out in R band on 25 nights ...
  • PDS microdensitometer at Indian Institute of Astrophysics 
    Sagar, R; Srinivasan, R (Tata Institute of Fundamental Research, 1988)
  • Performance of the IIA mosaic CCD camera system 
    Naidu, B. N; Srinivasan, R; Mohan, V; Sagar, R (Astronomical Society of India, 2001)
    We evaluate performance of the 4K x 4K mosaic CCD camera system developed at the Indian Institute of Astrophysics using four Thomson CCDs in a buttable configuration. The camera system consists of a mosaic CCD dewar developed ...
  • Photoelectric and electronographic photometry of the globular cluster NGC 1851 
    Sagar, R; Cannon, R. D; Hawkins, M. R. S (Royal Astronomical Society, 1988-05)
    The colour-magnitude diagram for NGC 1851 is presented to a limit of V = 21.0 mag, approximately 2 mag below the main-sequence turn-off point, on the basis of UBV photoelectric photometry and electronographic BV photometry. ...
  • Photometric Performance of the CCD Detector at the Kavalur 102-CM Reflector 
    Sagar, R; Pati, A. K (Astronomical Society of Indian, 1989-03)
    A CCD detector system built around the Thomson TH 7882 chip has recently been acquired for use at the 102 cm telescope at the Vainu Bappu Observatory (VBO). The chip has a coating for enhanced ultraviolet sensitivity, ...
  • Photometric Variability of Four Coronally Active Stars 
    Pandey, J. C; Singh, K. P; Sagar, R; Drake, S. A (Indian Academy of Sciences, 2002-03)
    We present photometric observations of four stars that are optical counterparts of soft X-ray/EUV sources, namely 1ES 0829+15.9, 1ES0920-13.6, 2RE J110159+223509 and 1ES 1737+61.2. We have discovered periodic variability ...
  • Photometry and low resolution spectroscopy of hot post-AGB candidates 
    Gauba, G; Parthasarathy, M; Kumar, B; Yadav, R. K. S; Sagar, R (The European Southern Observatory, 2003-06)
    We have obtained Johnson U, B, V and Cousins R, I photometry and low resolution spectra of a small sample of hot post-AGB candidates. Using the present data in combination with JHK data from 2MASS, infrared data from the ...
  • Polarization Measurements of Some Herbig Ae / Be-Stars 
    Jain, S. K; Bhatt, H. C; Sagar, R (International Astronomical Union, 1990)
    We have measured the linear polarization of 8 bright Herbing Ae/ Be starsin UBVRI bands. No unique wavelength dependence of magnitude as well as direction is found on these measurements.
  • Possible Microlensing Event in the direction of M31 
    Joshi, Y. C; Pandey, A. K; Narasimha, D; Sagar, R (Astronomical Society of India, 2003)
    The Cousin R and I band photometric observations of ~ 13 x 13 field in the direction of M31 galaxy have been carried out during 1999-2001 to search for microlensing events using pixel technique. Here we report a microlensing-like ...
  • A possible scenario for the formation of the composite Large Magellanic Cloud star cluster NGC 2214 
    Bhatt, H. C; Sagar, R (Astronomical Society of India, 1992)
    The total masses and relaxation times for the two stellar populations (old and young) in the star cluster NGC 2214 are estimated. The total masses are found to be comparable. While the older population may be dynamically ...
  • Probable binary open star clusters in the Galaxy. 
    Subramaniam, A; Gorti, U; Sagar, R; Bhatt, H. C (EDP Science, 1995-10)
    The existence of double/binary clusters in the Magellanic Clouds is fairly well established, whereas only one such pair, h + χ Persei, is known in the Galaxy. From the catalogues of open clusters of the Galaxy, we have ...
  • Profile fitting for the stellar photometry 
    Sagar, R (Tata Institute of Fundamental Research, 1988)
    The point spread functions used for doing photometry on two-dimensional stellar images are described. Analytical functions used for this purpose are discussed and it is indicated that amongst them modified Lorentzian fits ...
  • Prolonged intranight optical quiescence of the classical BL Lac object PKS 0735+178 
    Goyal, A; Gopal-Krishna; Anupama, G. C; Sahu, D. K; Sagar, R; Britzen, S; Karazous, M; Aller, M. F; Aller, H. D (Astronomical Society of the Pacific, 2009-09)
    We report our extensive intranight optical monitoring of the well known low-energy peaked (LBL) BL Lac object PKS 0735+178. This long-term follow-up consists of R-band monitoring for a minimum duration of ˜ 4 hours, on 17 ...
  • Proposed microthermal measurements at Devasthal 
    Pant, P; Sagar, R (Astronomical Society of India, 1998)
  • The Puppis OB III association: polarization measurements 
    Bhatt, H. C; Jain, S. K; Sagar, R (European Southern Observatory, 1998-03)
    Optical linear polarization measurements of association members and field stars in the region of the Puppis OB III association are presented. The association members are found to have larger values of polarization than the ...

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