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Browsing IIAP Publications by Author "Sagar, R"

Browsing IIAP Publications by Author "Sagar, R"

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  • The 3.6 metre Devasthal optical telescope: from inception to realization 
    Sagar, R; Kumar, Brijesh; Omar, A (Indian Academy of Sciences, 2019-08-10)
    India’s largest 3.6 metre Devasthal Optical Telescope (DOT) was commissioned in 2016, though the idea of building it germinated way back in 1976. This article provides research accounts as well as glimpses of its nearly ...
  • 3.6-m Devasthal Optical Telescope Project: Completion and first results 
    Kumar, Brijesh; Omar, A; Maheswar, G; Pandey, A. K; Sagar, R; Uddin, W; Sanwal, B. B; Bangia, T; Kumar, T. S; Yadav, S; Sahu, S; Pant, J; Reddy, B. K; Gupta, A. C; Chand, H; Pandey, J. C; Joshi, M. K; Jaiswar, M; Nanjappa, N; Purushottam; Yadav, R. K. S; Sharma, S; Pandey, S. B; Joshi, S; Joshi, Y. C; Lata, S; Mehdi, B. J; Misra, K; Singh, M (Societe Royale des Sciences de Liege, 2018-04)
    We present an update on the 3.6-m aperture optical telescope, which has been installed at Devasthal in the year 2016. In this paper, a brief overview of installation activities at site and first results are presented. The ...
  • The 4-m International Liquid Mirror Telescope 
    Surdej, J; Hickson, P; Borra, E; Swings, J; Habraken, S; Akhunov, T; Bartczak, P; Chand, H; De Becker, M; Delchambre, L; Finet, F; Kumar, B; Pandey, A; Pospieszalska, A; Pradhan, B; Sagar, R; Wertz, O; De Cat, P; Denis, S; de Ville, J; Jaiswar, M. K; Lampens, P; Nanjappa, N; Tortolani, J (Societe Royale des Sciences de Liege, 2018-04)
    The 4-m International Liquid Mirror Telescope (ILMT) is presently (March-June 2017) being erected on the ARIES site in Devasthal (Uttarakhand). We describe and illustrate in the present paper its different components. ...
  • ARIES, Nainital: a strategically important location for climate change studies in the Central Gangetic Himalayan region 
    Sagar, R; Dumka, U. C; Naja, M; Singh, N; Phanikumar, D. V (Indian Academy of Sciences, 2015-08-25)
    ARIES, acronym for Aryabhatta Research Institute of Observational Sciences, located in the Central Gangetic Himalayan (CGH) region is emerging as one of the unique sites for climate change studies. The long-term, in situ, ...
  • CCD photometry in VRI bands of the galactic cluster NGC 2818 
    Surendiranath, R; Kameswara Rao, N; Sagar, R; Nathan, J. S; Ghosh, K. K (Indian Academy of Sciences, 1990-06)
    The open cluster NGC 2818 containing a planetary nebula has been observed in VRI bands using the CCD system at prime focus of the 2.3 meter Vainu Bappu Telescope. The study extending to stars V of 21 magnitude established ...
  • CCD Photometry of NGC 2453 
    Mallik, D. C. V; Sagar, R; Pati, A. K (International Astronomical Union, 1993)
  • CCD photometry of the distant southern globular cluster NGC 5824 
    Cannon, R. D; Sagar, R; Hawkins, M. R. S (Royal Astronomical Society, 1990-03)
    A V, (B-V) C-M diagram for the distant globular cluster NGC 5824 is obtained from CCD observations of 285 stars reaching V = 20.5. Assuming a reddening of E(B-V) = 0.13, the color of the giant branch at the level of the ...
  • CCD photometry of the distant young open cluster NGC 7510 
    Sagar, R; Griffiths, W. K (Royal Astronomical Society, 1991-06)
    CCD observations in B, V, and I passbands have been used to generate deep V, (B-V), and V,(V-I) color-magnitude diagrams for the open cluster NGC 7510. The sample consists of 592 stars reaching down to V = 21 mag. There ...
  • Changing look AGN Mrk 590: broad-line region and black hole mass from photometric reverberation mapping 
    Amit Kumar Mandal; Schramm, Malte; Rakshit, Suvendu; Stalin, C. S; Vijarnwannaluk, Bovornpratch; Rujopakarn, Wiphu; Poshyachinda, Saran; Kouprianov, Vladimir V; Haislip, Joshua B; Reichar, Daniel E; Sagar, R; Mathew, Blesson (Oxford University Press on behalf of Royal Astronomical Society, 2021-12)
    We present the results of photometric reverberation mapping observations on the changing look active galactic nucleus Mrk 590 at z = 0.026. The observations were carried out from 2018 July to December using broad-band B-, ...
  • A complete photometric study of the open cluster NGC 7790 containing Cepheid variables 
    Gupta, A. C; Subramaniam, A; Sagar, R; Griffiths, W. K (EDP Sciences, 2000-09)
    CCD photometry of the northern open star cluster NGC 7790 has been carried out in BVI photometric passbands down to V ~ 21 mag for 1150 stars of which for ~ 700 stars, the data is obtained for the first time. We derive the ...
  • 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 ...
  • A comprehensive study of the rich open star cluster NGC 2099 based on deep BVI CCD observations 
    Nilakshi; Sagar, R (E D P Sciences, 2002-01)
    The CCD observations of the rich open star cluster NGC 2099 and its surrounding field region have been carried out up to a limiting magnitude of V ~ 22 mag in B, V and I passbands for the first time. A total of ~ 12 000 ...
  • 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, ...
  • A deep BVI photometric study of the open cluster NGC 2453 
    Mallik, D. C. V; Sagar, R; Pati, A. K (EDP Sciences, 1995-12)
    CCD observations of the open cluster NGC 2453 have been carried out in B, V and I passbands. A total of 356 stars have been observed in a field of about 4'x6' of the sky centred on the cluster. Colour-magnitude diagrams ...
  • A deep UBVRI CCD photometric study of the moderately young southern open star cluster NGC 4755 = Kappa-Crucis 
    Sagar, R; Cannon, R. D (The European Southern Observatory, 1995-05)
    CCD observations in U, B, V, R and I passbands have been used to generate (U-B), (B-V) colour-colour and deep V, (B-V); V, (U-B) and V, (V-I) colour-magnitude diagrams for the young open cluster NGC 4755. The sample consists ...
  • A deep UBVRI CCD photometric study of the open clusters Tr1 and Be 11 
    Yadav, R. K. S; Sagar, R (Royal Astronomical Society, 2002-11)
    We present deep UBVRI charge-coupled device (CCD) photometry for the young open star clusters Tr1 and Be11. The CCD data for Be11 are obtained for the first time. The sample consists of ~1500 stars reaching down to V~ 21 ...
  • Determination of the size of the dust torus in H0507+164 through optical and infrared monitoring 
    Amit Kumar; Rakshit, S; Kshama, S. K; Stalin, C. S; Mathew, B; Hoenig, Sebastian; Gandhi, Poshak; Sagar, R; Pandge, M. B (Oxford University Press on behalf of the Royal Astronomical Society, 2018-04)
    The time delay between flux variations in different wavelength bands can be used to probe the inner regions of active galactic nuclei (AGNs). Here, we present the first measurements of the time delay between optical and ...
  • Dust reverberation mapping of Z229–15 
    Mandal, A. K; Rakshit, S; Stalin, C. S; Wylezalek, D; Patig, M. K; Sagar, R; Mathew, B; Muneer, S; Pal, I (Oxford University Press on behalf of the Royal Astronomical Society, 2021-03)
    We report results of the dust reverberation mapping (DRM) on the Seyfert 1 galaxy Z229–15 at z = 0.0273. Quasi-simultaneous photometric observations for a total of 48 epochs were acquired during the period 2017 July to ...
  • 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 ...
  • Emission-line CCD imaging of three southern symbiotic stars 
    Bhatt, H. C; Sagar, R (Indian Academy of Sciences, 1991-06)
    Symbiotic stars that are strong radio sources and have cool dust emitting in the IR are expected to have extended emission nebulae around them. In order to search for such emission nebulae, CCD imaging of three symbiotic ...

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