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Browsing IIAP Publications by Author "Sagar, R"

Browsing IIAP Publications by Author "Sagar, R"

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  • 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 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)
  • 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 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.
  • 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 ...
  • 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 ...
  • Quasar catalogue for the astrometric calibration of the forthcoming ILMT survey 
    Mandal, A. K; Pradhan, Bikram; Surdej, Jean; Stalin, C. S; Sagar, R; Mathew, B (Indian Academy of Sciences, 2020-12)
    Quasars are ideal targets to use for astrometric calibration of large scale astronomical surveys as they have negligible proper motion and parallax. The forthcoming 4-m International Liquid Mirror Telescope (ILMT) will ...
  • Radial distribution of the integrated light and photometric colours in open star clusters 
    Sagar, R; Bhatt, H. C (Indian Academy of Sciences, 1989-06)
    Mass segregation in the form of preferential concentration of more massive stars in the central regions of a number of open star clusters has been known for some time. In this paper, integrated UBV colors in concentric ...
  • Radio, millimeter and optical monitoring of GRB 030329 afterglow: constraining the double jet model 
    Resmi, L; Ishwara-Chandra, C. H; Castro-Tirado, A. J; Bhattacharya, D; Rao, A. P; Bremer, M; Pandey, S. B; Sahu, D. K; Bhatt, B. C; Sagar, R; Anupama, G. C; Subramaniam, A; Lundgren, A; Gorosabel, J; Guziy, S; de Ugarte Postigo, A; Castro Cerón, J. M; Wiklind, T (EDP Sciences, 2005-09)
    We present radio, millimeter and optical observations of the afterglow of GRB 030329. $UBVR_{\rm C}I_{\rm C}$ photometry is presented for a period of 3 h to 34 days after the burst. Radio monitoring at 1280 MHz has been ...
  • Rapid optical variability of TeV blazars 
    Gopal-Krishna; Goyal, A; Joshi, S; Karthick, C; Sagar, R; Wiita, P. J; Anupama, G. C; Sahu, D. K (Wiley-Blackwell, 2011-09)
    In this first systematic attempt to characterize the intranight optical variability (INOV) of TeV-detected blazars, we have monitored a well-defined set of nine TeV blazars on total 26 nights during 2004–10. In this R- or ...
  • REMAP: Determination of the inner edge of the dust torus in AGN by measuring time delays 
    Mandal, A. K; Rakshit, S; Pal, I; Stalin, C. S; Sagar, R; Mathew, B. (Societe Royale des Sciences de Liege, 2019-10)
    Active galactic nuclei (AGN) are high luminosity sources powered by accretion of matter onto super-massive black holes (SMBHs) located at the centres of galaxies. According to the Unification model of AGN, the SMBH is ...
  • SAO 75669: A late type giant behind the molecular cloud MBM 12 
    Bhatt, H. C; Sagar, R; Subramaniam, A; Gorti, U; Chandrasekhar, T; Ashok, N. M; Ragland, S (European Southern Observatory, 1994-09)
    Photometric and spectroscopic observations of the star SAO 75669 in the region of the high galactic latitude molecular cloud MBM 12 are presented. The optical, near-infrared and far-infrared IRAS photometric magnitudes ...
  • Science at high-altitude sites of ARIES-astrophysics and atmospheric sciences 
    Sagar, R; Naja, M; Maheswar, G; Srivastava, A. K (Indian National Science Academy, 2014-11)
    In this article we discuss various frontline research activities those are being carried out in the fields of Astronomy and Astrophysics and Atmospheric Sciences at Aryabhatta Research Institute of Observational Sciences ...

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