IIA Institutional Repository: Recent submissions

  • Gain calibration of CCD systems at VBO 
    Prabhu, T. P; Mayya, Y. D; Anupama, G. C (Indian Academy of Sciences, 1992-03)
    The system gain of two CCD systems in regular use at the Vainu Bappu Observatory, Kavalur, is determined at a few gain settings. The procedure used for the determination of system gain and base-level noise is described in ...
  • Effects of rotation on the colours and line indices of stars. VI - The reality of the blue straggler phenomenon 
    D'Souza, J; Mathew, Annamma; Rajamohan, R (Indian Academy of Sciences, 1992-03)
    The effect of rotation on the observed colors of stars has been considered as a possible cause for the blue straggler phenomenon in clusters listed by Mermilliod (1982). It appears that this phenomenon is definitely not ...
  • Effects of rotation on the colours and line indices of stars. V - The ZRMS and the ZRZAMS 
    Mathew, Annamma; Rajamohan, R (Indian Academy of Sciences, 1992-03)
    The observed uvby and H-beta indices of member stars of the Hyades and Praesepe clusters are analyzed in detail for rotation. The slopes of the rotation effects observed are utilized to determine the zero rotation main ...
  • The solar dynamo with meridional circulation. 
    Choudhuri, A. R; Schussler, M; Dikpati, M (1995-11)
    We show that meridional circulation can have a profound influence on dynamo models for the solar cycle. Motivated by the observed tilt angles of sunspot groups we assume that the generation of the poloidal field takes place ...
  • Kinetic Equilibria of Accretion Discs 
    Bhaskaran, P; Krishan, V (Springer, 1995-10)
    A kinetic description of the equilibrium structure of accretion disc plasma is presented. It is possible to have an equilibrium configuration for a stationary axisymmetric gravitating plasma disc with spatial gradients in ...
  • Lunar Occulations with Infrared Arrays 
    Chandrasekhar, T; Shah, R; Mondal, S (Astronomical Society of India, 2003)
    Recently we have successfully observed the lunar occulation of a carbon star IRC+20120 and a M5 star IRC+10241 with the NICMOS sub array at the 1.2m Gurushikhar telescope. The integration times were respectively 5 millisec ...
  • Optical CCD imaging of some Herbig Ae/Be stars 
    Bhatt, H. C; Sagar, R (EDP Sciences, 1992-02)
    Results of V, R, and H-alpha CCD imaging for 15 Herbig Ae/Be stars are presented. Light variations of more than about 2 mag in V have been noticed in stars T Ori, RR Tau, and LH-alpha 25. The nature of the variations in ...
  • Infrared L'band (lambda-cen- ~3.9 mu-m) observations with TIFR near-infrared camera (TIRCAM). 
    Ojha, D. K; Ghosh, S. K; Verma, R. P; Anandarao, B. G (Astronomical Society of India, 2003)
    TIRCAM is based on the SBRC InSb Focal Plane Array (58 x 62 pixels) sensitive between 1- 5 μm. TIRCAM system is described in Ojha et al. (2002). TIRCAM had its first light observations during March-April 2001 from Gurusikhar ...
  • Near Infrared PICNIC Imager (NIPI) - A Progress Report 
    Deep, A; Ramaprakash, A. N; Tandon, S. N; Gupta, R; Burse, M. P; Chordia, P. A; Das, H. K; Engineer, S; Kohok, A. A; Mestry, V. B (Astronomical Society of India, 2003)
    In the ASI 2002 meeting we presented a preliminary design of Near Infrared PICNIC Imager (Deep et al, 2002). In this paper we will show the progress that has been made since then.
  • 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 ...
  • On the Resolving Power of an Echelle Grating in the Presence of a Corrugated Wavefront of Incidence 
    Chatterjee, S; Banyal, R. K; Prasad, B. R; Chandrasekharan, K (Astronomical Society of India, 2003)
  • Photometric calibration of the CCD camera of 1-m telescope at VBO 
    Mayya, Y. D (Indian Academy of Sciences, 1991-12)
    Calibration of the CCD camera of the 1-m telescope at the Vainu Bappu Observatory, Kavalur, to the BVR system is reported here based on the observations of stars in the 'dipper asterism' in the open cluster M 67 (NGC 2682). ...
  • Polarization measurements of stars in the region of the nearby molecular cloud MBM 12 
    Bhatt, H. C; Jain, S. K (Blackwell Publishing, 1992-07)
    Linear polarization measurements of stars in the region of the nearby high-latitude molecular cloud MBM 12 are presented. Stars behind the cloud show a polarization of about 2-3 percent, while stars that are in front of ...
  • Model of planetary motion in the works of Kerala astronomers 
    Ramasubramanian, K (Astronomical Society of India, 1998)
    In this report, we discuss the significant advances in planetary theory made by the Kerala astronomers during 14th to 18th centuries. A geometrical picture of planetary motion, where the five planets Mercury, Venus, Mars, ...
  • An Extended Matched Filtering Method to Detect Periodicities in a Rough Grating for Extremely Large Roughness 
    Vani, V. C; Chatterjee, S (Astronomical Society of India, 2003)
    Matched filtering algorithm has beenshown by us to be an effective method to detect hidden periodicities in a rough grating, extending detectability to regimes of higher roughness than was hitherto known. The above matched ...
  • Mid-ultraviolet and optical photometry of helium stars 
    Kilambi, G. C; Nagar, P; Kameswara Rao, N (Indian Academy of Sciences, 1992-06)
    Mid-ultraviolet and optical photometric analysis of helium stars are presented. A linear relation exists between the effective temperature derived from model atmospheres and (1965-V)0 index. The effective temperatures ...
  • Distribution of stars perpendicular to the plane of the Galaxy 
    Chatterjee, S (Indian Academy of Sciences, 1991-12)
    A detailed calculation is given of the distribution of mass above the Galactic plane for any arbitrary mass distribution and velocity distribution. It is shown that an analytic expression can be found for the gravitational ...
  • Performance Evaluation of Adaptive Optics Systems 
    Sridharan, R; Raja Bayanna, A; Srivastava, N; Kumar, B; Ravindra, B; Gupta, S. K; Jain, N; Ambastha, A; Venkatakrishnan, P (Astronomical Society of India, 2003)
    Adaptive Optics (AO) systems improve the resolution of ground based telescopes and allow for long exposure images. Their performance depends on the seeing conditions at the time of observations. In this paper, we evaluate ...
  • Night Sky Extinction Measurements at the Indian Astronomical Observatory, Hanle 
    Parihar, P. S; Sahu, D. K; Bhatt, B. C; Subramaniam, A; Anupama, G. C; Prabhu, T. P (Astronomical Society of India, 2003)
    We present the estimates of the night sky extinction at the Indian Astronomical Observatory. Also presented are the estimates of the night sky brightness. The extinction in the U band at IAO is found to be lower than the ...
  • The pancasiddhantika of Varahamihira : A puzzling problem is its presently available text 
    Sarma, K. V (Astronomical Society of India, 1998)
    It is pointed out that Pancasiddhantika of Varahamihira lacks lacks the sequential and logical arrangement of topics as found in his other works like Brhajjataka. It is concluded that the presently available version might ...

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