Research Papers: Recent submissions

  • 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 ...
  • Distribution of Hα flares during solar cycle 23 
    Joshi, B.; Pant, P. (2005)
    The paper presents the results of an analysis of the north-south (N−S) and east-west (E−W) distribution of Hα solar flares from 1996 to 2003. This period of investigation corresponds to the ascending phase, the maximum and ...
  • Intermediate-term periodicities in soft x-ray flare index during solar cycles 21, 22 and 23 
    Joshi, B.; Joshi, A. (2005)
    We have analyzed the intermediate-term periodicities in soft X-ray flare index (FIsₓR) during solar cycles 21, 22 and 23. Power-spectral analysis of daily FIsₓR reveals a significant period of 161 days in cycle 21 which ...
  • Optical and x-ray studies of chromospherically active stars: FR cancri, HD 95559, and lo pegasi 
    Pandey, J. C.; Singh, K. P.; Drake, S. A.; Sagar, R. (2005-09)
    We present a multiwavelength study of three chromospherically active stars, namely, FR Cnc (BD +16º1753), HD 95559, and LO Peg (BD +22º4409), including newly obtained optical photometry and low-resolution optical spectroscopy ...
  • Naini Tal – Cape survey for pulsating chemically peculiar stars – A status report 
    Seetha, S.; Chaubey, U. S.; Girish, V.; Joshi, S.; Ashoka, B. N.; Gupta, S. K.; Kurtz, D. W.; Martinez, P.; Sagar, R. (2001)
    The “Naini Tal-Cape survey for rapidly oscillating Ap stars”, to search the northern hemi-sphere sky for pulsating stars was initiated in 1997. This is a collaboration between India and South Africa. So far about 70 stars ...
  • Radio, millimeter and optical monitoring of GRB 030329 afterglow: Constraining the double jet model 
    Resmi, L., ... et al. (including Pandey, S. B. and Sagar, R.) (2005)
    We present radio, millimeter and optical observations of the afterglow of GRB 030329. UBVR˓I˓ photometry is presented for a period of 3 h to 34 days after the burst. Radio monitoring at 1280 MHz has been carried out using ...
  • Optical follow-up of GRB afterglows from UPSO, Naini Tal 
    Pandey, S. B.; Sagar, R.; Mohan, V.; Pandey, A. K.; Bhattacharya, D.; Castro-Tirado, A. J. (2001)
    Successful optical photometric observations of live GRB afterglows namely GRB 990123, GRB 991216, GRB 000301c and GRB 000926 have been carried out from State Observatory Naini Tal till 2000. the reesults and light curve ...
  • UPSO three channel fast photometer 
    Gupta, S. K.; Sagar, R.; Joshi, S.; Ashoka, B. N.; Babu, V. C.; Seetha, S.; Girish, V. (2001)
    The design and performance of a modular portable three channel fast photometer is described. It can be disassembled as single individual channels such that the system can also be used as a single channel photometer. The ...
  • Performance of the IIA mosaic CCD camera system 
    Naidu, B. N.; Srinivasan, R.; Mohan, V.; Sagar, R. (2001)
    We evaluate performance of the 4K x 4K mosaic CCD camera system development at the Indian Institute of Astrophysics using four Thomson CCDs in a buttable configuration. The cameras system consists of a mosaic CCD dewar ...
  • New pulsating variables discovered from the Naini Tal-Cape Survey 
    Seetha, S.; Ashoka, B. N.; Joshi, S.; Girish, V.; Sagar, R.; Chaubey, U. S.; Gupta, S. K. (2002)
    The Naini Tal-Cape survey has been initiated to search for pulsations in chemically peculiar A and F type stars. Many of the magnetic A peculiar type stars exhibit rapid oscillations with periods ranging from 4-16 minutes. ...
  • 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. (2005)
    We present UBV CCD photometry and low-resolution spectra of stars in the field of the young open cluster NGC 146.We estimated 10–16 Myr as the turn-off age for the upper main sequence of the cluster using isochrones and ...
  • SS 433: Results of a recent multiwavelength campaign 
    Chakrabarti, S. K.; Anandarao, B. G.; Pal, S.; Mondal, S.; Nandi, A.; Bhattacharyya, A.; Mandal, S.; Sagar, R.; Pandey, J. C.; Pati, A.; Saha, K. (2005)
    We conducted a multiwavelength campaign in 2002 September–October, to observe SS 433. We used the Giant Meter Radio Telescope for radio observations, the Physical Research Laboratory Infrared Telescope at Mt Abu for infrared ...
  • On the analysis of light curves in asteroseismology 
    Mary, D. L. (2005)
    We provide a detailed introduction to the main problems arising when analyzing light curves in asteroseismology. Attention is first paid to the signal model delivered by the pulsating stars and to the noise sources corrupting ...
  • 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 ...
  • The Nainital–cape survey: A search for variability in Ap and Am stars 
    Joshi, S. (2005)
    The “Nainital–Cape Survey” program for searching photometric variability in chemically peculiar (CP) stars was initiated in 1997 at ARIES, Nainital. We present here the results obtained to date. The Am stars HD98851, ...
  • Multi-wavelength observations of an unusual impulsive flare associated with CME 
    Uddin, W.; Jain, R.; Yoshimura, K.; Chandra, R.; Sakao, T.; Kosugi, T.; Joshi, A.; Despande, M. R. (2004)
    We present the results of a detailed analysis of multi-wavelength observations of a very impulsive solar flare 1B/M6.7, which occurred on 10 March, 2001 in NOAA AR 9368 (N27 W42). The observations show that the flare is ...
  • Intranight optical variability of BL Lacs, radio-quiet quasars and radio-loud quasars 
    Stalin, C. S.; Gupta, A. C.; Gopal-Krishna; Wiita, P. J.; Sagar, R. (2005)
    We report monitoring observations of 20 high- luminosity active galactic nuclei (AGN), 12 of which are radio-quiet quasars (RQQs). Intranight optical variability (INOV) was detected for 13 of the 20 objects, including ...
  • Wintertime spatial characteristics of boundary layer aerosols over peninsular India 
    Moorthy, K. K., ...et al. (including Saha, A.) (2005-04-30)
    During an intense field campaign for generating a spatial composite of aerosol characteristics over peninsular India, collocated measurements of the mass concentration and size distribution of near-surface aerosols were ...
  • A comparative study of the intra-night optical variability of powerful AGNs 
    Stalin, C. S.; Gopal-Krishna; Sagar, R.; Wiita, P. J. (2002)
    In order to address a currently much debated issue, we are carrying out a systematic search for intra-night optical micro-variability in major classes of powerful (Mᵥ ≥ -23.0 mag)active galactic nuclei (AGNs). Our sample ...
  • On mass and velocity distributions in members of star clusters: an analytical approach 
    Chatterjee, S.; Kumar, B.; Sagar, R. (2002)
    Dynamical evolution of stellar mass distribution in star clusters is analysed by considering simultaneously the effects of dynamical friction, stochastic heating and the gravitational potential due to mass distribution in ...

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