IIA Institutional Repository: Recent submissions

  • Search for HI Reionization Epoch in the Early Universe 
    Swarup, G (Astronomical Society of India, 2003)
    One of the most challenging problems in astronomy today is to search for reionization of the neutral hydrogen (HI), which is expected to occur somewhere between redshifts of about 6 to 20. The reionization is likely to ...
  • Dissipative Collapse of a Spherical Cluster of Gas Clouds 
    Indulekha, K; Vijayagovindan, G. V; Ramadurai, S (Astronomical Society of India, 2003)
    We investigate the time scale for the dissipative collapse of a spherical cluster of gas clouds by supplementing the scalar virial equation with an evolution equation for the energy. We find that collapse times are more ...
  • A Statistical Study of 3EG Source Characteristics 
    Sharma, M; Kaul, R. K (Astronomical Society of India, 2003)
    A detailed statistical study of 3EG source characteristics and their variation as a function of galactic latitude shows that a majority of Unidentified sources at mid galactic latutudes are so-far undetected AGN.
  • Polarization Asymmetry in CSS Sources 
    Saikia, D. J; Gupta, N (Astronomical Society of India, 2003)
    We show that the compact steep spectrum sources are more asymmetric in the polarization of the outer lobes compared with the more extended ones. This could be due to interaction of the jets with infalling material, which ...
  • An Expanding Plasma Model for the X-ray/radio knots in KPC-scale Jets of Active Galactic Nuclei 
    Sahayanathan, S; Misra, R; Kembhavi, A. K; Kaul, C. L (Astronomical Society of India, 2003)
    We model the observed X-ray/radio knots in Active Galactic Nuclei (AGN) as isotropically expanding spherical plasma clouds fed continously by non-thermal electrons. The time-dependent electron distribution and the emitted ...
  • Anomalously high apparent abundances of singly ionized helium in the Galactic H II region W3A 
    Roelfsema, P. R; Goss, W. M; Mallik, D. C. V (University of Chicago Press, 1992-07)
    The distribution of single ionized helium Y(+) in the Galactic H II region W3A has been determined using high-resolution observations of radio recombination lines in the 76, 92, and 110 alpha lines. The angular resolutions ...
  • Some consequences of quadratic gravity for the early universe 
    Sivaram, C; Campanelli, M (Springer Netherlands, 1992-06)
    The hypothesis that gravity at very high energies and, hence, around the Planck epoch in the early universe is described by an action quadratic in the curvature, asymptotically free in the coupling is explored. It is shown ...
  • Cool star flux spectra for population studies in galaxies 
    Malagnini, M. L; Morossi, C; Buser, R; Parthasarathy, M (EDP Sciences, 1992-08)
    Five solar-composition cool giant stars have been observed with the IUE low resolution mode. The UV energy distributions were merged with visual spectrophotometry from the literature and compared with predictions from two ...
  • The influence of a vertical magnetic field on oscillations in an isothermal stratified atmosphere 
    Hasan, S. S; Christensen-Dalsgaard, J (University of Chicago Press, 1992-09)
    The effect of a uniform vertical magnetic field on the modes of an isothermal stratified atmosphere is examined. The general solutions of the wave equation for an isothermal magnetized medium are given. Asymptotic expansions ...
  • Geometrical optics and diffraction vis-a-vis Mie theory of scattering of electromagnetic radiation by a sphere 
    Shah, G. A (Springer Netherlands, 1992-07)
    The usefulness of the classical Geometrical Optics and Diffraction (GOD) has been illustrated for scattering of electromagnetic radiation by very large dielectric and absorbing spheres. Various scattering parameters such ...
  • Hard X-ray characteristics of solar flares using electron Monte-Carlo calculations and beamed thick target model 
    Rausaria, R. R (Springer Netherlands, 1992-08)
    The experimental results of X-ray bursts with spectral characteristics, spatial distribution, fast time variations, polarization, and directivity measurements carried out with Intercosmos, PVO/ISEE-3 spacecrafts, imaging ...
  • Solar eclipses - A powerful tool for the study of nature 
    Bhattacharyya, J. C (National Institute of Science Communication and Information Resources, 1990-12)
    Solar eclipses occur due to periodic coincidences in positions of the moon and the earth with respect to the sun. Characteristics of their orbital paths determine the periodicity, duration and shape, lengths and orientations ...
  • Spectroscopic survey of field stars : A search for metal-poor stars 
    Giridhar, S; Goswami, A (Astronomical Society of India, 2002)
    We have undertaken a spectroscopic survey of field stars to fine metal-poor objects among them. Though the main objective of the survey is to find new metal-poor stars, stellar parameterization is carried out for all the ...
  • A Study of Giant Radio Galaxies 
    Konar, C; Saikia, D. J; Ishwara-Chandra, C. H; Kulkarni, V. K (Astronomical Society of India, 2003)
    Multi-frequency radio observations have been made of a sample of 17 giant radio galaxies, many of whose structures were not well determined earlier. These sources were observed with the VLA D- and B/C arrays at C and L ...
  • Magnetic Field Geometry of 3C111 on pc-scales 
    Kharb, P; Gabuzda, D; Shastri, P (Astronomical Society of India, 2003)
    Multi-epoch Very Long Baseline Polarimetric observations of the Broad Line Radio galaxy 3C111 performed at 8 and 43 GHz after a large millimetre outburst, reveal rapidly evolving parsec-scale radioo structure and the ...
  • The chemical composition of the high velocity POST AGB star HD 56126(F5I) 
    Parthasarathy, M; Lario, P. G; Pottasch, S. R (EDP Sciences, 1992-10)
    From an analysis of high-resolution spectra of the IRAS source HD 56126 (F5I), it is found that its photospheric abundances of C, O, S are nearly solar and N is overabundant by about -0.2 dex. The abundance of Fe and related ...
  • IR observations of Am stars 
    Shylaja, B. S; Ashok, N. M (Astronomical Society of India, 2002)
    The IR observations of chemically peculiar stars are carried out and compared with the previous data in IR and far IR from IRAS. The flux redistribution appears to be a common phenomenon in all the stars of this class. The ...
  • Spectroscopy of Seyferts in the Far-UV 
    Shastri, P; Murthy, J; Hutchings, J (Astronomical Society of India, 2003)
    We present our preliminary far-ultraviolet spectra of the Seyfert Mrk 533 obtained with FUSE. These are among the first FUV spectra of a purportedly edge-on Seyfert, and show narrow OVI emission as well as some evidence ...
  • Low Frequency Observations of a Head-Tail Radio Source 
    Vir Lal, D; Pramesh Rao, A (Astronomical Society of India, 2003)
    We have mapped the head-tail radio galaxy, 3C 129 at 240 and 610 MHz using the GMRT and studied the detailed morphology and spectral index variations in this object. This is the first attempt to observe a sample of head-tail ...
  • Radio Study of a Superwind-galaxy: NGC1482 
    Hota, A; Saikia, D. J (Astronomical Society of India, 2003)
    We present GMRT and VLA observations of the superwind galaxy, NGC1482, which has been discovered to have a remarkable hour-glass shaped optical emission line outflow on both sides of the galactic disk. The central region ...

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