IIA Institutional Repository: Recent submissions

  • FG Sagittae: A Newborn R Coronae Borealis Star? 
    Gonzalez, G; Lambert, D. L; Wallerstein, G; Kameswara Rao, N; Smith, V. V; McCarthy, J. K (The American Astronomical Society, 1998-01)
    We have monitored FG Sge's spectroscopic changes since the time just prior to its dramatic fading in 1992 August. The most significant qualitative changes in the spectrum include large variations in the strength of the C2 ...
  • VI CCD photometry of metal-rich globular clusters: NGC 6528 
    Richtler, T; Grebel, E. K; Subramaniam, A; Sagar, R (European Southern Observatory, 1998-01)
    We present CCD photometry in V and I for the metal-rich globular cluster NGC 6528. A comparison with previous photometry reveals discrepancies of the order 0.1 to 0.2 mag in V, emphasizing the need for independent photometry. ...
  • Charged particle trajectories in a toroidal magnetic and rotation-induced electric field around a black hole 
    Sengupta, S (World Scientific Publishing Company, 1997-10)
    Trajectories of charged particles in a combined poloidal, toroidal magnetic field and a rotation-induced unipolar electric field superposed on a Schwarzschild background geometry have been investigated extensively in the ...
  • Application of the effective valence shell Hamiltonian method to accurate estimation of oscillator strengths and excitation energies of Mg-like ions 
    Chaudhuri, R. K; Das, B. P; Freed, K. F (American Institute of Physics, 1998-02)
    The ab initio effective valence shell Hamiltonian (Hυ) method is used to compute the excitation energies and oscillator strengths for resonance transitions in Mg-like ions, as well as their lowest ionization potentials. ...
  • On the line ratio diagnostics for NeV, MgV, SiVII and Mg VII solar ions 
    Dwivedi, B. N; Mohan, Anita; Raju, P. K (Elsevier, 1997)
    We present NeV/MgV and MgVII/SiVII theoretical line intensity ratios as a function of electron density and temperature for physical conditions within the solar chromosphere-corona transition region. The electron pressure ...
  • Short-Term Optical Variability in Broad Absorption Line QSOs 
    Anupama, G. C; Chokshi, A (The American Astronomical Society, 1998-02)
    We present the first results from a pilot program to monitor the short-term optical variability in broad absorption line system QSOs. Intranight optical variations of 5% were detected on timescales of 1 hr in QSOs 0846+156 ...
  • On the development of abnormally large postsunset upward drift of equatorial F region under quiet geomagnetic conditions 
    Sastri, J. H (American Geophysical Union, 1998-03)
    The regular postsunset enhancement of upward drift of the equatorial F region is observed to be abnormally large on certain quiet days (Ap ≤ 5) as manifested by an anomalous dusktime increase of F region height. We explored ...
  • The Puppis OB III association: polarization measurements 
    Bhatt, H. C; Jain, S. K; Sagar, R (European Southern Observatory, 1998-03)
    Optical linear polarization measurements of association members and field stars in the region of the Puppis OB III association are presented. The association members are found to have larger values of polarization than the ...
  • Correlations of Faint Galaxies: A Monte Carlo Approach 
    Chokshi, A (The American Astronomical Society, 1998-03)
    Monte Carlo methods are employed to study the angular correlations arising from simulated galaxy clusters in flux-limited samples. In particular, we show that the models of Chokshi and coworkers that best reproduce the ...
  • Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XII. Ground-based Monitoring of 3C 390.3 
    Dietrich, M; Peterson, B. M; Albrecht, P; Altmann, M; Barth, A. J; Bennie, P. J; Bertram, R.; Bochkarev, N. G; Bock, H; Braun, J. M; Burenkov, A; Collier, S; Fang, L. Z; Francis, O. P; Filippenko, A. V; Foltz, C. B; Gaessler, W; Gaskell, C. M; Geffert, M; Ghosh, K. K; Hilditch, R. W; Honeycutt, R. K; Horne, K; Huchra, J. P; Kaspi, S; Kuemmel, M; Leighly, K. M; Leonard, D. C; Malkov, Yu. F; Mikhailov, V; Miller, H. R; Morrill, A. C; Noble, J; O'Brien, P. T; Oswalt, T. D; Pebley, S. P; Pfeiffer, M; Pronik, V. I; Qian, B. C; Robertson, J. W; Robinson, A.; Rumstay, K. S; Schmoll, J; Sergeev, S. G; Sergeeva, E. A; Shapovalova, A. I; Skillman, D. R; Snedden, S. A; Soundararajaperumal, S; Stirpe, G. M; Tao, J; Turner, G. W; Wagner, R. M; Wagner, S. J; Wei, J. Y; Wu, H.; Zheng, W; Zou, Z. L (The American Astronomical Society, 1998-04)
    Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V, R, and I), the spectrophotometric optical continuum flux F lambda (5177 A), and the integrated ...
  • The 1995-96 decline of R Coronae Borealis: high-resolution optical spectroscopy 
    Kameswara Rao, N; Lambert, D. L; Adams, M. T; Doss, D. R; Gonzalez, G; Hatzes, A. P; James, C. R; Johns-Krull, C. M; Luck, R. E; Pandey, G; Reinsch, K; Tomkin, J; Woolf, V. M (The Royal Astronomical Society, 1999-12)
    A set of high-resolution optical spectra of R CrB acquired before, during and after its 1995-96 decline is discussed. All of the components reported from earlier declines are seen. This novel data set provides new information ...
  • The R Coronae Borealis stars - atmospheres and abundances 
    Asplund, M; Gustafsson, B; Lambert, D. L; Kameswara Rao, N (European Southern Observatory, 2000-01)
    An abundance analysis of the H-deficient and He- and C-rich R Coronae Borealis (R CrB) stars has been undertaken to examine the ancestry of the stars. The investigation is based on high-resolution spectra and line-blanketed ...
  • Birth and early evolution of a planetary nebula 
    Bobrowsky, M; Sahu, K. C; Parthasarathy, M; García-Lario, P (Nature Publishing Group, 1998-04)
    The final expulsion of gas by a star as it forms a planetary nebula - the ionized shell of gas often observed surrounding a young white dwarf - is one of the most poorly understood stages of stellar evolution,. Such nebulae ...
  • Long-Wavelength Observations of Jets from Polar Regions of the Sun 
    Ramesh, R (Kluwer Academic Publishers, 1999-10)
    We report radio observations of enhanced emission associated with the extreme-ultraviolet (EUV) jets from polar coronal hole regions of the Sun, with the Gauribidanur radioheliograph (GRH). We have estimated the brightness ...
  • The Correlation Lifetimes of Chromospheric CA II K Network Cells 
    Raju, K. P; Srikanth, R; Singh, J (Springer, 1998-03)
    The lifetimes and spatial scales of emission network cells in the solar chromosphere were studied from a nearly continuous sequence of Caii K filtergrams, obtained from Antarctica. The temporal autocorrelation function ...
  • A Correlative Study of Green Coronal Intensity with Other Solar Indices 
    Ramesh, K. B (Springer, 1998-01)
    Lomnicky Stit data of 5303 U coronal green-line index (CI) are analysed for the years 1965–1994. The yearly quiet-Sun component (Q_ci) of CI estimated through the linear regression analysis of CI with sunspot numbers (SS) ...
  • Measurement of Kodaikanal white-light images - IV. Axial Tilt Angles of Sunspot Groups 
    Sivaraman, K. R; Gupta, S. S; Howard, R. F (Kluwer Academic Publishers, 1999-10)
    The Kodaikanal sunspot data set, covering the interval 1906-1987, is used in conjunction with the similar Mount Wilson sunspot data set, covering the interval 1917-1985, to examine characteristics of sunspot group axial ...
  • Cp-Violation in Epr-Like Neutrino Oscillations 
    Samal, M. K (World Scientific Publishing Company, 1998-03)
    After reviewing the general framework to study EPR-like neutrino oscillations, we derive expressions for the oscillation probabilities and a direct measure of CP-violation. We compare the possibility of studying CP-violation ...
  • Cosmological QCD phase transition and dark matter 
    Bhattacharyya, A; Alam, J; Sarkar, S; Roy, P; Sinha, B; Raha, S; Bhattacharjee, P (Elsevier, 1999-12)
    The authors calculate the size distribution of quark nuggets, which could be formed due to first order QCD phase transition in the early universe. They find that there are a large number of stable quark nuggets which could ...
  • Gyroscopic Precession and Inertial Forces in Axially Symmetric Stationary Spacetimes 
    Rajesh Nayak, K; Vishveshwara, C. V (Springer, 1998-04)
    We study the phenomenon of gyroscopic precession and the analogues of inertial forces within the framework of general relativity. Covariant connections between the two are established for circular orbits in stationary ...

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