IIA Institutional Repository: Recent submissions

  • Upper Limits on O VI Emission from Voyager Observations 
    Murthy, M (Indian Academy of Sciences, 2002-06)
    We have examined 426 Voyager fields distributed across the sky for O VI (1032/1038 Å) emission from the Galactic diffuse interstellar medium. No such emission was detected in any of our observed fields. Our most constraining ...
  • Spectroscopic Studies of the Solar Corona II. Properties of Green and Red Emission Lines in Open and Closed Coronal Structures 
    Singh, J; Sakurai, T; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Takeda, Aki (Astronomical Society of Japan, 2002-10)
    We obtained profiles of the green (Fe <FONT SIZE="-2">XIV 5303Å) and red (Fe <FONT SIZE="-2">X 6374Å) emission lines simultaneously on 1998 July18-19 for about 4hours with a cadence of 10minutes, covering an area of about ...
  • Multi-band Observations of Gamma Ray Bursts 
    Bhargavi, S. G (Indian Academy of Sciences, 2002-06)
    This talk focuses on the various aspects we learnt from multiband observations of GRBs both, before and during the afterglow era. A statistical analysis to estimate the probable redshifts of host galaxies using the luminosity ...
  • Detection of Zinc in the Very Metal-Poor Post-AGB Star HR 4049 
    Takeda, Yoichi; Parthasarathy, M; Aoki, W; Ita, Yoshifusa; Nakada, Yoshikazu; Izumiura, Hideyuki; Noguchi, Kunio; Takada-Hidai, Masahide; Sato, B; Tajitsu, Akito; Honda, Satoshi; Kawanomoto, Satoshi; Ando, Hiroyasu; Karoji, Hiroshi (Astronomical Society of Japan, 2002-10-25)
    We report on the detection of two Zn I lines at 4722.15Å and 4810.53Å in the high-quality spectrum of the very metal-poor post-AGB star HR 4049, which was obtained with the High Dispersion Spectrograph attached to the ...
  • A deep UBVRI CCD photometric study of the open clusters Tr1 and Be 11 
    Yadav, R. K. S; Sagar, R (Royal Astronomical Society, 2002-11)
    We present deep UBVRI charge-coupled device (CCD) photometry for the young open star clusters Tr1 and Be11. The CCD data for Be11 are obtained for the first time. The sample consists of ~1500 stars reaching down to V~ 21 ...
  • Nature of Tilt Angles of Sunspot Groups During the 22nd Solar Cycle 
    Muneer, S; Singh, J (Springer, 2002-10)
    Daily white-light images from Kodaikanal Observatory have been utilized to study the nature of tilt angles of sunspot groups during the 22nd solar cycle. 2416 spot groups have been measured to find the tilt angle. An average ...
  • EUV diagnostics for boron-like ions from spectra obtained by SUMER/SOHO 
    Mohan, A; Dwivedi, B. N (Astronomical Society of India, 2002-09)
  • Short-term periodicities in the north-south asymmetry of the Sun's surface rotation 
    Javaraiah, J (Astronomical Society of India, 2002-09)
    Power spectra of N-S asymmetries of the coefficients A and (j of the Sun's surface differential rotation determined from the Mt. Wilson velocity data during 1982-1994 suggest the existence of a period at 374 ± 30 day in ...
  • Three Dimensional Structure of Active Regions 
    Choudhary, D. P; Gosain, S (Astronomical Society of India, 2002-09)
    We present the preliminary results of the modeling of the three dimensional structure of the magnetic field above the aclive regions observed with Advanced Stokes polarimeter and Dick Dunn telescope at National ...
  • Imaging With The Mauritius Radio Telescope Challenges and Results 
    Udaya Shankar, N; Golap, K; Sachdev, S; Dodson, R; Katwaroo, M; Sastry, Ch. V (Springer, 2002)
    The Mauritius Radio Telescope (MRT) has been built with the main objective of surveying the southern sky at meter wavelengths. MRT is a Fourier synthesis, T-shaped non-coplanar array. It consists of a2048 m long East-West ...
  • The Mass Function of Young Star Clusters in our Galaxy and Nearby Galaxies: Is It Universal? 
    Sagar, R (International Astronomical union, 2002)
    Mass functions (MFs) derived from photometric observations of young star clusters of our Galaxy, the Magellanic Clouds (MCs), M31 and M33 have been used to investigate the question of universality of the initial mass ...
  • Spectroscopic Observation of Coronal Waves 
    Sakurai, T; Ichimoto, K; Raju, K. P; Singh, J (Springer, 2002-10)
    A time sequence over 80 min of coronal green-line spectra was obtained with a corona- graph at the Norikura Solar Observatory. Doppler velocities, line intensities, and line widths were derived through fitting a single ...
  • On the Out of Phase Appearance of Large-Scale Diffuse Magnetic Field of the Sun with Respect to Sunspots 
    Dikpati, M; Choudhuri, A. R (Kluwer Academic Publishers, 1996-03)
    We assume the large-scale diffuse magnetic field of the Sun to originate from the poloidal component of a dynamo operating at the base of the convection zone, whereas the sunspots are due to the toroidal component. The ...
  • Estimation of Fried's Parameter From Specklegrams of Solar Features 
    Sridharan, R; Venkatakrishnan, P; Verma, V. K (Springer, 2002-12)
    A few methods of estimating Fried's parameter (r 0) from specklegrams of solar features are described. Some of these methods were used to estimate r 0 for the speckle data obtained from Kodaikanal Observatory (KO), Uttar ...
  • Magnetic and velocity fields over active regions 
    Gosain, S; Choudhary, D. B (Astronomical Society of India, 2002-09)
    In order to understand the nature of dynamics over an active region (AR) , it is necessary to study the velocity and magnetic fields simultaneously. We present the preliminary results from our analysis of spectropolari ...
  • Dynamical Effects in Solar Photospheric Flux Tubes 
    Hasan, S. S (Kluwer Academic Publisher, 1996)
    The interaction of an intense flux tube, extending vertically through the photosphere, with p-modes in the ambient medium is modelled by solving the time dependent MHD equations in the thin flux tube approximation. It is ...
  • Observability of Coronal Heating Processes 
    Venkatakrishnan, P (Kluwer Academic Publishers, 1996)
    The mechanisms that could possibly heat the corona are briefly reviewed with emphasis on their observability. Observing enhanced wave flux at footpoints of active regions would confirm wave heating. Observation of nonthermal ...
  • A Near Infrared Photometric Study of the Young Orion Nebula Star Cluster NGC 1976 
    Qian, Z. Y; Sagar, R (Royal Astronomical Society, 1994-01)
    We have measured the JHK magnitudes of 47 stars in the region of the extremely young Orion nebula star cluster NGC 1976. These, in combination with the existing near-infrared and optical data, are used to study the ...
  • Temporal variations of solar p-mode frequencies on time scales of 27 days 
    Tripathy, S. C; Jain, K; Bhatnagar, A (Astronomical Society of India, 2002-09)
    We have studied variations in the frequencies of intermediate degree solar oscillation modes on a time cadence of 18 and 27 days. We report that the p-modes adjust to changes in the activity measures on time scales as ...
  • Mutual phenomena of the Galilean satellites: an analysis of the 1991 observations from VBO 
    Vasundhara, R (European Southern Observatory, 1994-01)
    Results of analysis of seventeen mutual events, of the Galilean satellites, observed at the Vainu Bappu Observatory (VBO) during the 1991 are presented. The light curves were fitted with theoretical models to derive the ...

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