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Browsing by Author "Sagar, R."

Browsing by Author "Sagar, R."

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  • Comprehensive multiwavelength modelling of the afterglow of GRB 050525A 
    Resmi, L. et. al.; Pandey, S. B.; Sagar, R. (2012)
    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 BV I CCD observations 
    Nilakshi; Sagar, R. (2002)
    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 ...
  • A deep UBVRI CCD photometry study of the open clusters Tr 1 and Be 11 
    Yadav, R. K. S.; Sagar, R. (2002)
    We present deep UBVRI charge-coupled device (CCD) photometry for the young open star cluster Tr 1 and Be 11. the CCD data for Be 11 are obtained for the first time. The sample consists of ~1500 stars reaching down to V ~ ...
  • A deep VI CCD photometric study of the neglected galactic star cluster NGC 6631 
    Sagar, R.; Naidu, B. N.; Mohan, V. (2001)
    We present the VI CCD photometric observations of about 5500 stars up to a limiting magnitude of V~ 20 in an area of ~16'⨯16' around the cluster NGC 6631. The cluster parameters determined for the first time by fitting the ...
  • Determining field correlations produced by stars from the study of special changes in double slit experiment 
    Kandpal, H. C.; Mehta, D. S.; Gopal, E. S. R.; Vaishya, J. S.; Sanwal, B. B.; Singh, M.; Sagar, R. (2001)
    Experiments are performed to determine the coherence properties of wave fields, produced by the broadband stellar sources on the earth surface, from the study of spectral changes produced on interference in the Young’s ...
  • Development of a three channel photometer for UPSO, Naini Tal 
    Ashoka, B. N.; Kumar; Babu, V. C.; Seetha, S.; Girish, V.; Gupta, S. K.; Sagar, R.; Joshi, S.; Narang, P. (2001)
    The design and performance of a portable three channel photometer installed at the Uttar Pradesh State Observatory (UPSO), NainiTal is described. The photometer is modular and the whole unit can be disassembled as individual ...
  • Development of Mie LIDAR system and initial cloud observations over Central Himalayan region 
    Bangia, T.; Kumar, A.; Sagar, R.; Agarwal, P. K.; Singh, K. (Scientific Research and Essays, 2011-02-18)
    Aryabhatta Research Institute of Observational Sciences (ARIES) at Manora Peak (29° 22’ N, 79° 27’ E), Nainital is located in the Central Himalayan region at an altitude of ~ 1950 m. This free tropospheric site away from ...
  • Discovery of pulsations in HD 98851 
    Joshi, S.; Girish, V.; Martinez, P.; Sagar, R.; Ashoka, B. N.; Gupta, S. K.; Seetha, S.; Chaubey, U. S.; Kurtz, D. W. (2001)
    Using the UPSO 1- m Sampurnanand reflector telescope equipped with a fast photometer, we observed the chemically peculiar (CP) star HD 98851 for a total of around 30 hours on 5 different nights between January to April ...
  • Discovery of pulsations in the Am star HD 13079 
    Martinez, P.; Kurtz, D. W.; Ashoka, B. N.; Chaubey, U. S.; Gupta, S. K.; Leone, F.; Catanzaro, G.; Sagar, R.; Raj, E.; Seetha, S.; Kasturirangan, K. (1999)
    Pulsation in cool main-sequence Am stars is a rare phenomenon observed in a few marginal Am stars and only one classical Am star. The chemically peculiar star HD 13079 is shown to be pulsating with a 78-min period and a ...
  • Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480 
    Joshi, S.; Girish, V.; Sagar, R.; Kurtz, D. W.; Martinez, P.; Kumar, B.; Seetha, S.; Ashoka, B. N.; Zhou, A. (2003)
    The chemically peculiar (CP) stars HD 98851 and HD 102480 have been discovered to be unusual pulsators during the ‘Naini Tal–Cape Survey’ programme to search for pulsational variability in CP stars. Time series photometric ...
  • 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. (2004)
    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 ...
  • Effect of mass segregation on mass function of young open clusters 
    Pandey, A. K.; Mahra, H. S.; Sagar, R. (1992)
    The effect of mass segregation on cluster mass function has been studied and it is found that the slope of the mass function is steeper in the outer part of the open clusters. Since derived dynamical relaxation time is ...
  • Emissions from GRBs and their afterglows: Indian observations 
    Sagar, R. (2001)
    The study of Gamma-ray bursts, electromagnetically the most luminous events in the Universe though only for a few seconds, was revolutionized in 1997 when the Italian-Dutch X-ray satellite BeppoSAX started providing the ...
  • Facilities at ARIES for the Nainital–cape survey 
    Sagar, R.; Mary, D. L. (2005)
    A collaborative programme searching for mmag pulsations in chemically peculiar stars in the northern hemisphere was initiated in 1997 between Nainital, India, and Cape Town, South Africa. It was therefore named as the ...
  • Field star contamination in open star cluster NGC 2301 
    Mohan, V.; Sagar, R. (1988)
    Photographic photometry of about 900 stars down to V = 17 mag has been carried out in the region of the open clusters NGC 2301. The cluster region seems to be severely contaminated by fields stars. Statistical criteria ...
  • First microlensing candidate towards M 31 from the Nainital microlensing survey 
    Joshi, Y. C.; Pandey, A. K.; Narasimha, D.; Sagar, R. (2005)
    We report our first microlensing candidate NMS-E1 towards M 31 from the data accumulated during the four years of Nainital Microlensing Survey. Cousin R and I band observations of ∼13´ × 13´ field in the direction of M ...
  • First simultaneous measurements of ozone, CO, and NOy at a high-altitude regional representative site in the central Himalayas 
    Sarangi, Tapaswini; Naja, Manish; Ojha, N.; Kumar, R.; Lal, S.; Venkataramani, S.; Kumar, A.; Sagar, R.; Chandola, H.C. (AGU Publication, 2014-02-06)
    Simultaneous in situ measurements of ozone, CO, and NOy have been made for the first time at a high altitude site Nainital (29.37°N, 79.45°E, 1958 m above mean sea level) in the central Himalayas during 2009–2011. CO ...
  • 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. (2003)
    We present the UBVRc I c 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, A.; Krishna, G.; Sagar, R.; Anupama, G. C.; Sahu, D. K. (2007)
    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 ...
  • GRB 000301C with peculiar afterglow emission 
    Sagar, R.; Mohan, V.; Pandey, S. B.; Pandey, A. K.; Stalin, C. S.; Castro-Tirado, A. J. (2000)
    The CCD magnitude in Johnson V and Cousins R and I photometric passbands are determined for GRB 000301C afterglow starting ~ 1.5 day after the γ – ray burst. In fact we provide the earliest optical observations for this ...

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