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Browsing Publications based on data from IAO, Hanle by Author "Sagar, R"

Browsing Publications based on data from IAO, Hanle by Author "Sagar, R"

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  • Comprehensive multiwavelength modelling of the afterglow of GRB 050525A 
    Resmi, L; Misra, K; Johannesson, G; Castro-Tirado, A. J; Gorosabel, J; Jelınek, M; Bhattacharya, D; Kubanek, P; Anupama, G. C; Sota, A; Sahu, D. K; de Ugarte Postigo, A; Pandey, S. B; Sanchez-Ramırez, R; Bremer, M; Sagar, R (Wiley-Blackwell, 2012-11)
    The Swift era has posed a challenge to the standard blast-wave model of gamma-ray burst (GRB) afterglows. The key observational features expected within the model are rarely observed, such as the achromatic steepening ...
  • The dark nature of GRB 051022 and its host galaxy 
    Castro-Tirado, A. J; Bremer, M; McBreen, S; Gorosabel, J; Guziy, S; Fakthullin, T. A; Sokolov, V. V; González Delgado, R. M; Bihain, G; Pandey, S. B; Jelínek, M; de Ugarte Postigo, A; Misra, K; Sagar, R; Bama, P; Kamble, A. P; Anupama, G. C; Licandro, J; Pérez-Ramírez, D; Bhattacharya, D; Aceituno, F. J; Neri, R (EDP Sciences, 2007-11)
    Aims.We present multiwavelength (X-ray/optical/near-infrared/millimetre) observations of GRB 051022 between 2.5 h and ~1.15 yr after the event. It is the most intense gamma-ray burst (~10-4 erg cm-2) detected by HETE-2, ...
  • Early optical and millimeter observations of GRB 030226 afterglow 
    Pandey, S. B; Sagar, R; Anupama, G. C; Bhattacharya, D; Sahu, D. K; Castro-Tirado, A. J; Bremer, M (EDP Sciences, 2004-04)
    The CCD magnitudes in Johnson UBV and Cousins RI photometric passbands for the afterglow of the long duration GRB 030226 are presented. Upper limits of a few mJy to millimeter wave emission at the location of optical are ...
  • A flattening in the optical light curve of SN 2002ap 
    Pandey, S. B; Anupama, G. C; Sagar, R; Bhattacharya, D; Sahu, D. K; Pandey, J. C (Royal Astronomical Society, 2003-04)
    We present the UBVRcIc broad-band optical photometry of the Type Ic supernova SN 2002ap obtained during 2002 February 6-March 23 in the early decline phases and also later on 2002 August 15. Combining these data with the ...
  • Further evidence for intra-night optical variability of radio-quiet quasars 
    Goyal, Arti; Gopal-Krishna; Sagar, R; Anupama, G. C; Sahu, D. K (Astronomical Society of India, 2007-06)
    Although well established for BL Lac objects and radio-loud quasars, the occurrence of intra-night optical variability (INOV) in radio-quiet quasars is still debated, primarily since only a handful of INOV events with good ...
  • 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. ...
  • 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 ...
  • A multiwavelength study of star formation in the vicinity of galactic H II region Sh 2-100 
    Samal, M. R; Pandey, A. K; Ojha, D. K; Ghosh, S. K; Kulkarni, V. K; Kusakabe, N; Tamura, M; Bhatt, B. C; Thompson, M. A; Sagar, R (The American Astronomical Society, 2010-05)
    We present multiwavelength investigation of morphology, physical-environment, stellar contents, and star formation activity in the vicinity of star-forming region Sh 2-100. It is found that the Sh 2-100 region contains ...
  • NGC 146: a young open cluster with a Herbig Be star and intermediate mass pre-main sequence stars 
    Subramaniam, A; Sahu, D. K; Sagar, R; Vijitha, P (EDP Sciences, 2005-09)
    We present UBV CCD photometry and low-resolution spectra of stars in the field of the young open cluster NGC 146. UBV photometry of 434 stars were used to estimate the E(B-V) reddening of 0.55 $\pm$ 0.04 mag and BV photometry ...
  • The optical afterglow of the not so dark GRB 021211 
    Pandey, S. B; Anupama, G. C; Sagar, R; Bhattacharya, D; Castro-Tirado, A. J; Sahu, D. K; Parihar, P. S; Prabhu, T. P (The European Southern Observatory, 2003-09)
    We determine Johnson B,V and Cousins R,I photometric CCD magnitudes for the afterglow of GRB 021211 during the first night after the GRB trigger. The afterglow was very faint and would have been probably missed if no prompt ...
  • Optical and near-infrared photometric study of the open cluster NGC 637 and 957 
    Yadav, R. K. S; Kumar, B; Subramaniam, A; Sagar, R; Mathew, B (Royal Astronomical Society, 2008-11)
    We present UBVRI CCD photometry in the region of the open clusters NGC 637 and 957. The radii are found to be 4.2 and 4.3 arcmin. Their reddenings E(B - V) are 0.64 +/- 0.05 and 0.71 +/- 0.05 mag and their distances, from ...
  • 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 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 ...
  • 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 ...
  • SN 2002ap, the Hypernova of Class Ic 
    Pandey, S. B; Sahu, D. K; Anupama, G. C; Bhattacharya, D; Sagar, R (Astronomical Society of India, 2003)
    The supernova SN 2002ap was discovered in the outer regions of the nearby spiral M74 on January 29.4 UT. Early photometric and spectroscopic observations indicate the supernova belongs to the class of Ic hypernova. Late ...
  • 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 ...

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