IIA Institutional Repository: Recent submissions

  • Multi-colour optical monitoring of the intra-day variable blazar S5 0716+71 
    Sagar, R; Gopal-Krishna; Mohan, V; Pandey, A. K; Bhatt, B. C; Wagner, S. J (The European Southern Observatory, 1999-02)
    We report multi-colour optical monitoring of the intra-day variable blazar S5 0716+71 with a dense temporal coverage over a total duration of 4 weeks in February/March 1994. Four filters (BV Johnson and RI Cousins) were ...
  • Cerenkov radiation emitted by charged particles in a gravitational field 
    Gupta, A; Mohanty, S; Samal, M. K (Institute of Physics, 1999-01)
    Charged particles propagating in an external gravitational field with negative Ricci tensor components can emit radiation by the Cerenkov process. The external gravitational field acts like an effective refractive index ...
  • 5303Å Coronal Irradiance and Its Relation to the Photospheric Magnetic Activity 
    Ramesh, K. B (Kluwer Academic Publishers, 1998-12)
    The association of Lomnický Štít data of coronal green line irradiance (CI) to photospheric magnetic activity is studied for the years 1975-1994 using the Carrington rotation averaged photospheric magnetic flux data. It ...
  • Role of time resolution on polarization of pulsar radiation 
    Gangadhara, R. T; Xilouris, K. M; von Hoensbroech, A; Kramer, M; Jessner, A; Wielebinski, R (The European Southern Observatory, 1999-02)
    The role of orthogonal polarization modes in pulsar emission is re-examined in view of polarization data of high time resolution. Individual pulse data of PSR B1133+16 at 1.41 GHz, obtained with time resolutions of 1160, ...
  • N-Body Simulation of a Deeply Penetrating Collision Between Unequal Galaxies 
    Namboodiri, P. M. S; Sastry, K. S; Narasimhan, K. S. V. S (Kluwer Academic Publishers, 1998-09)
    We study the tidal effects of a deeply penetrating collision between two spherical galaxies, one twice massive but less dense than the other, by numerical simulations. We consider the relative motion of the galaxies to be ...
  • Ether, Luminosity and Galactic Source Counts 
    Tomaschitz, R (Kluwer Academic Publishers, 1998-08)
    An interpretation of the cosmological redshift in terms of a cosmic ether is given. We study a Robertson-Walker cosmology in which the ether is phenomenologically defined by a homogeneous and isotropic permeability tensor. ...
  • Implications of kHz quasi-periodic brightness oscillations in X-ray binaries for neutron star structure 
    Thampan, A. V; Bhattacharya, D; Datta, B (Blackwell Science Ltd., 1999-02)
    Kilohertz quasi-periodic oscillations (QPOs) in low-mass X-ray binaries (LMXBs) may represent the orbital frequencies of the innermost Keplerian orbits around accreting neutron stars. Attempts have recently been made to ...
  • The spectrum of the cool R Coronae Borealis variable Z Ursae Minoris at minimum 
    Goswami, A; Kameswara Rao, N; Lambert, D. L (The Observatory, 1999-02)
  • Hybrid approach to relativistic Gaussian basis functions: Theory and applications 
    Chaudhuri, R. K; Panda, P. K; Das, B. P (The American Physical Society, 1999-02)
    We present a hybrid method to solve the relativistic Hartree-Fock-Roothan equations where the one- and two-electron radial integrals are evaluated numerically by defining the basis functions on a grid. This procedure reduces ...
  • Multicolor CCD Photometry and Stellar Evolutionary Analysis of NGC 1907, NGC 1912, NGC 2383, NGC 2384, and NGC 6709 Using Synthetic Color-Magnitude Diagrams 
    Subramaniam, A; Sagar, R (The American Astronomical Society, 1999-02)
    We present the first CCD photometric observations of NGC 2383 and NGC 2384 in B, V, R, and I, NGC 1912, NGC 6709 in B, V, and I and NGC 1907 in B and V passbands, reaching down to a limiting magnitude of V~20 mag for ~3300 ...
  • V, I CCD photometry of metal-rich bulge globular clusters: NGC 6553 
    Sagar, R; Subramaniam, A; Richtler, T; Grebel, E. K (The European Southern Observatory, 1999-03)
    We have carried out VI CCD photometry of about 40 000 stars down to V ~ 23 mag in an area of about 6' x 10' centered on the metal-rich Galactic bulge globular cluster NGC 6553 and an adjacent field region. Our photometry ...
  • Late-type giants with infrared excess. I. Lithium abundances 
    Jasniewicz, G; Parthasarathy, M; de Laverny, P; Thévenin, F (European Southern Observatory, 1999-02)
    de la Reza et al. (1997) suggested that all K giants become Li-rich for a short time. During this period the giants are associated with an expanding thin circumstellar shell supposedly triggered by an abrupt internal mixing ...
  • Steady and fluctuating parts of sun's internal magnetic field 
    Gokhale, M. H; Hiremath, K. M (International Astronomical Union, 1993-01)
    We have modeled the 'steady' part of sun's internal poloidal magnetic field in the form of a central dipole and a central hexapole with strengths (0.6 +/- 0.1)B(o)R(0) exp 3 and (0.16 +/- 0.05)B(o)R(0) exp 5 embedded in ...
  • A seismic model of the solar convective envelope 
    Shibahashi, H; Hiremath, K. M; Takata, M (International Astronomical Union, 1998)
    We deduce the density, pressure, and temperature profiles in the solar convective envelope by solving the basic equations for mass conservation and the hydrostatic equilibrium with the imposition of the helioseismologically ...
  • Dynamical phenomena in sunspots. I. Time dependent relaxation to equilibrium 
    Gangadhara, R. T; Hasan, S. S (European Southern Observatory, 1997-11)
    We have adapted a general purpose time-dependent 2-D code to study dynamical phenomena in sunspots. In the first part of our investigation, we numerically simulate the dynamical relaxation to equilibrium of a sunspot. ...
  • Determination of the atmospheric point spread function by a parameter search 
    Krishnakumar, V; Venkatakrishnan, P (European Southern Observatory, 1997-12)
    The result of blind deconvolution is a reconstructed image that has non positive intensities. The number of these non positive pixels has been used as an estimator for the departure from a perfect reconstruction. Simulations ...
  • The chemical composition of IRAS 05341+0852: a post-AGB F supergiant with 21 MU M emission 
    Reddy, B. E; Parthasarathy, M; Gonzalez, G; Bakker, E. J (European Southern Observatory, 1997-12)
    An abundance analysis of the photosphere of the F-type Post-AGB candidate IRAS 05341+0852 is presented. The analysis of the spectra suggests that the atmospheric model: Teff=6500 K, log g=0.5, xi_ {t}=5 km s(-1) and ...
  • Post-Maximum Optical and Infrared Observations of Nova V1425 Aquilae 1995 
    Kamath, U. S; Anupama, G. C; Ashok, N. M; Chandrasekhar, T (American Astronomical Society, 1997-12)
    We present the post-maximum optical spectroscopy and infrared photometry of Nova V1425 Aquilae 1995. The data indicate that the nova belongs to the Fe ii class and that it formed an optically thin dust shell at a very early ...
  • Active Galactic Nuclei and Galaxy Formation 
    Chokshi, A (The American Astronomical Society, 1997-12)
    It is proposed that early jet-induced activity around active galactic nuclei (AGNs) is responsible for triggering large-scale star formation in protogalaxies and results in the formation of giant ellipticals and spheroids ...
  • Weak emission line [WELS] central stars of planetary nebulae are [WC]-PG1159 stars 
    Parthasarathy, M; Acker, A; Stenholm, B (European Southern Observatory, 1998-01)
    The characteristics of the spectra of weak emission line stars (WELS) are found to be very similar to that of [WC]-PG1159 and PG1159 objects. On the basis of the spectra we find 31 WELS central stars of planetary nebulae ...

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