IIA Institutional Repository: Recent submissions

  • Our Present Understanding of Solar Flares 
    Dwivedi, B. N (Indian Institute of Astrophysics, Bangalore, 1986)
    A general discussion of solar flares with emphasis on two-ribbon flares is given. The basic differences between compact (simple-loop) and two-ribbon flares have also been pointed. Skylab observations have been presented ...
  • Measurement of Solar Magnetic Fields 
    Bhattacharyya, J. C; Balasubramaniam, K. S (Indian Institute of Astrophysics, Bangalore, 1986)
    The paper reviews several methods of estimation of solar magnetic fields so far employed. The possibility of measurement of the vector magnetic fields by using two dimensional detector arrays is discussed. A program for ...
  • Solar Optical Observations from Kodaikanal and from Eclipses 
    Singh, J (Indian Institute of Astrophysics, Bangalore, 1986)
    From an analysis of a long series of Calcium K spectroheliograms taken at Kodaikanal, systematic changes in the sizes of supergranule cells have been found. The average cell size changes with the phase of solar cycle, being ...
  • Ca II K Emission from the Solar Chromosphere 
    Sivaraman, K. R (Indian Institute of Astrophysics, Bangalore, 1986)
    The role of the Ca II K line as a reliable diagnostic of the chromospheric activity on the Sun is reviewed. The chromospheric structures seen in this line serve as good indicators of the photospheric magnetic structures ...
  • Optical Aspects of Solar Activity 
    Bhatnagar, A (Indian Institute of Astrophysics, Bangalore, 1986)
    A review of optical observations of some solar phenomena is presented. From the photospheric observations of the birth, growth and decay of pores, spots and sunspot groups and associated velocity and magnetic field structure ...
  • Notes for the Observer 
    Prabhu, T. P (Astronomical Society of India, 1982-12)
  • Integrated brightness and colour of Omega Centauri 
    Scaria, K. K (Astronomical Society of India, 1982-12)
    Integrated magnitudes in U, B, V, R and I bands are calculated for the globular cluseter Omega Centauri. The observed radial chaange in the integrated colour of the cluster shows that the cluster core (r<2') is redder in ...
  • Behaviour of some neutral molecular absorption lines in facula models 
    Tripathi, B. M; Sinha, K; Pande, M. C (Astronomical Society of India, 1982-12)
    The equivalent widths of some selected absorption lines of C2, Ch, MgH, NH, OH and SH molecules in five facula and two photospheric models have been calculated under the assumption of LTE. The calculations reveal that the ...
  • Vibration-rotation bands of SiH and MgH in sunspot spectra 
    Sinha, K; Joshi, G. C (Astronomical Society of India, 1982-12)
    We have calculated the equivalent widths of the vibration-rotation bands of SiH and MgH molecules for a possible detection in the sunspot spectrum. Five different models were utilized and the results obtained with and ...
  • Photometric solution for the eclipsing binary TT Aurigae 
    Abhyankar, K. D; Rajasekhar Rao, N; Lokanadham, B (Astronomical Society of India, 1982-12)
    Photometric elements of TT Aur are derived from the UBV observations of the star during 1973-77. The system is found to be detached but quite close. Absolute dimensions are obtained on the basis of the spectroscopic element ...
  • Light-time effect in AK Her and ER Ori 
    Abhyankar, K. D; Panchatsaram, T (Astronomical Society of India, 1982-12)
    An analysis of the minimum-time data of AK Her and ER Ori revelas possible sinudodal variations in their orbital periods. In the case of AK Her we suspect two additional components; one of mass 0.2 to 0.4 MSun with a period ...
  • Relativistic beams, thick accretion disks and active galactic nuclei 
    Wiita, P. J; Kapahi, V. K; Saikia, D. J (Astronomical Society of India, 1982-12)
    We review recent analyses of observations of radio galaxies and quasars that support the relativistic beaming models and appear to produce values for the Lorentz factors of the radiating mateiral in the nuclear jets. Thick ...
  • The Be star phenomena I. General properties 
    Kogure, T; Hirata, R (Astronomical Society of India, 1982-12)
    General properties of Be stars including their variabilities are considered. The Be stars are first defined as non-supergiant B stars with emission-lines including non-emission shell stars. The percentage fraction of Be/B ...
  • Tidal disruption in colliding galaxies 
    Narasimhan, K. S. V. S; Alladin, S. M (Astronomical Society of India, 1982-09)
    Distruptive effects in colliding galaxies due to their mutual tidal interaction are compared under the impulsive approximation. If M1 and M2 are the masses and Rho1 and Rho2 the densities of the two galaxies, M2 suffers ...
  • Analysis of the light variations of BS Aquarii 
    Kilambi, G. C (Astronomical Society of India, 1982-09)
    An analysis of UBV light variations of BS Aqr is presented. Intrinsic (U-B) and (B-V) values are used to derive the temperature and surface gravity. The mean values are Teff = 7600 + or - 100 K and log geff = 3.8 + or - ...
  • On MgH line intensities in sunspot unbrae 
    Sinha, K (Astronomical Society of India, 1982-09)
    The line intensities of the umbral MgH molecules reported by Sotirovski (1971) are re-analysed utilizing the latest laboratory data. It appears probable that because of a neglect of the role of blurring in producing stray ...
  • Places of formation of nineteen nearby classical Cepheids 
    Joshi, U. C (Astronomical Society of India, 1982-09)
    Places of formation of 10 nearby classical Cepheids have been computed in a model of our Galaxy which has axisymmetric and spiral-like components. For the axisymmetric components Schmidt's (1965) model is used, and spiral-like ...
  • Surge prominence of 1981 November 19 
    Verma, V. K; Pande, M. C (Astronomical Society of India, 1982-09)
    Time-lapse photographic observations with 0.7 Armstrong passband H-alpha filter and the morphological behaviour of the surge prominence recorded on 1981 Novermber 19 have been described. The surge was recorded both in the ...
  • Accretion disks - What do we know about them? 
    Prasanna, A. R (Astronomical Society of India, 1982-09)
    This essay briefly describes the present status of research on accretion disks around compact objects - in particular, blackholes - covering both the thin and thick disks. Significant results from various analyses regarding ...
  • The nature of the progenitors of supernovae of type I 
    van der Bergh, Sidney (Astronomical Society of India, 1982-09)
    This paper examines the hypothesis that supernovae of type I are produced by relatively 'young' single stars. The fact that SN I are not concentrated in spiral arms implies that their progenitors have M approximately less ...

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