IIA Institutional Repository: Recent submissions

  • Nonpotential magnetic fields at sites of gamma-ray flares 
    Hagyard, M. J; Venkatakrishnan, P; Smith, J. B. Jr (American Astronomical Society, 1990-06)
    The relation between the degree of nonpotentiality of photospheric magnetic fields and the occurrence of gama-ray flares is examined to determine whether there are special signatures of the stressed fields for this type ...
  • Equivalent widths of hydrogen Lyman alpha line in an expanding spherical atmosphere 
    Peraiah, A; Ingalgi, M. F (Indian Academy of Sciences, 1990-06)
    The profiles of hydrogen Lyman-alpha line in an expanding spherical atmosphere containing dust and gas were calculated. The variation of equivalent widths with velocities of expansion of the atmosphere, together with the ...
  • Effects of rotation on the colours and line indices of stars. II - The effect on UVBY and H-beta indices 
    Mathew, A; Rajamohan, R (Indian Academy of Sciences, 1990-06)
    The intrinsic uvby and H-beta indices of member stars of Alpha-Persei, Pleiades, and Scorpio-Centaurus association have been analyzed in detail for rotation effects. These stars range in spectral type from B0 to F0 and the ...
  • Influence of the solar activity on the Indian Monsoon rainfall 
    Hiremath, K. M; Mandi, P. I (Elsevier, 2004-10)
    We use 130 years data for studying correlative effects due to solar cycle and activity phenomena on the occurrence of the Indian Monsoon rainfall. We compute the correlation coefficients and significance of correlation ...
  • Quasi-Periodicity in global solar radio flux at metric wavelengths during Noise Storms 
    Sundaram, G. A. S; Subramanian, K. R (Springer, 2004-08)
    We present observational results from studying the quasi-periodicities in global solar radio flux during periods of enhanced noise storm activity, over durations of 4 hr a day (`intra-day'' variations), observed at 77.5 ...
  • 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 ...
  • Radiative transfer with Compton scattering in plane parallel geometry 
    Peraiah, A (Indian Academy of Sciences, 1990-06)
    The equation of radiative transfer with Compton scattering is solved. The specific intensity has been expanded by Taylor series with respect to wavelength and the first three terms have been retained in solving the transfer ...
  • Evolution of latitude zonal structure of the large-scale magnetic field in solar cycles 
    Makarov, V. I; Sivaraman, K. R (Springer, 1989-03)
    The latitude zonal component of the large-scale solar magnetic field is analyzed using H-alpha charts for the 1905-1982 period, and the poleward migration of prominences is used to calculate the time of reversal of the ...
  • The UV spectrum of the WC 11 star CPD -56 deg 8032 
    Kameswara Rao, N; Giridhar, S; Nandy, K (The European Southern Observatory, 1990-08)
    UV observations of the WC 11 central star of the compact planetary nebula CPD -56 deg 8032 show that the continuum flux is variable. This variability appears to be caused by a change in the circumstellar extinction properties. ...
  • Analysis of Ca(+) K plage area for short period variation 
    Singh, J; Jain, S. K (Indian Academy of Sciences, 1989-12)
    Observations of solar Ca(+) K daily plage area from 1951 to 1977 are analyzed to search for short-period (12-13 day) variations. The 27-day periodicity due to solar rotation modulation is found at all latitudes. Using an ...
  • A photometric study of F-type stars of high galactic latitude 
    Ferro, A. A; Giridhar, S; Chavez, M; Parrao, L (European Southern Observatory, 1989-04)
    Photometry in the O I 7774 A line and the uvbybeta system is presented for a group of high Galactic latitude F-type luminosity type I stars. The results indicate that the candidates are high gravity near solar Fe/H abundance ...
  • 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 ...
  • The ultraviolet spectrum of the hydrogen-poor binary HD 30353 
    Parthasarathy, M; Hack, M; Tektunali, G (The European Southern Observatory, 1990-04)
    An analysis is made of the high- and low-resolution UV spectra of the hydrogen-poor star HD 30353. The stellar wind profiles of the resonance lines of N V, C V, and Si IV are found to be similar to those observed in Upsilon ...
  • Second National Workshop on Solar Physics, Indian Institute of Astrophysics, Kodaikanal, India 
    Krishan, V; Sastry, Ch. V (Springer, 1989-09)
    This paper a brief report about the topics discussed at the second Indian national Workshop on Solar Physics held in September 1987
  • Supernova SN 1987A - Rotation rate of the central pulsar 
    Bhatt, H. C; Datta, B (Royal Astronomical Society, 1989-04)
    Using available observational data on supernova SN 1987A, firm quantitative lower limits on the rotation period of the central pulsar (assuming the pulsar luminosity to power the supernova light curve) are derived. It is ...
  • Occultations by possible material in Saturn's outer magnetosphere. II 
    Vasundhara, R (Indian Academy of Sciences, 1989-03)
    Results of a search for occultations of stars in the SAO catalog by Saturn's outer magnetosphere during 1989-1990 are presented. A total of nine events are predicted to occur during this period. The most favorable event ...
  • Tidal change in the energy of a spherical galaxy 
    Namboodiri, P. M. S; Kochhar, R. K (Royal Astronomical Society, 1990-03)
    Tidal effects of a massive perturber on a satellite galaxy have been studied by numerical simulations. The model consists of a spherical satellite galaxy and a point-mass perturber and the encounter is non-penetrating. A ...
  • An internally consistent set of oscillator strengths for Fe I lines 
    Giridhar, S; Ferro, A. A (Indian Academy of Sciences, 1989-03)
    An extensive set of internally consistent oscillator strength values for Fe I lines is compiled using literature data and scaling the oscillator strengths derived by different workers to that of Blackwell and his coworkers. ...
  • Sunspot activity as originating in interference of the sun's global MHD oscillations 
    Gokhale, M. H; Javaraiah, J (Royal Astronomical Society, 1990-03)
    Spherical-harmonic-Fourier (SHF) analysis of sunspot activity during 1902-54 show that the sunspot occurrence probability p(theta, phi, t) is given by superposition of, mainly, axisymmetric even degree SHF modes of l not ...
  • Tidal transfer of energy and angular momentum to spheroidal galaxies 
    Som Sunder, G; Kochhar, R. K; Alladin, S. M (Royal Astronomical Society, 1990-06)
    The tidal transfer of energy and angular momentum to a spheriodal test galaxy is studied using tensor virial equations within the framework of impulse approximation. The tidally introduced angular momentum is always along ...

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