IIA Institutional Repository: Recent submissions

  • IPS survey at 327 MHz for detection of compact radio sources 
    Balasubramanian, V; Janardhan, P; Ananthakrishnan, S; Manoharan, P. K (Astronomical Society of India, 1993)
    In early 1992 a new feed was installed along the focal line of the 530 m long and 30 m wide parabolic cylinder reflector of the Ooty Radio Telescope (ORT). The new feed consisting of 1056 GaAsFET low noise amplifiers, one ...
  • Photometry of X-ray selected quasars from Einstein Medium Sensitivity Survey 
    Singh, K. P; Bhat, P. N; Prabhu, T. P (Astronomical Society of India, 1993)
    We present a few photometric measurements of quasars in the Einstein Medium Sensitivity Survey (EMSS). The measurements are a part of an ongoing program of CCD photometry of quasars in the southern sky and are based on ...
  • Surface photometry of ellipticals: Radio and cluster galaxies 
    Singh, K. P; Bhat, P. N; Prabhu, T. P; Kembhavi, A. K (Astronomical Society of India, 1993)
    Broad-band surface photometry in V, R and I colors is presented for three elliptical galaxies immersed in hot intracluster gas emitting X-rays due to thermal bremsstrahlung. The galaxies are (1) a cD galaxy, and (2) a radio ...
  • Lenses of small angular scales from Jodrell Bank survey 
    Patnaik, A; Narasimha, D (Astronomical Society of India, 1993)
    The Jodrell Bank 5 GHz sky survey provides a complete flux-limited sample of radio sources at latitude greater than 2.5 deg which are brighter than 200 mJy and have a spectrum flatter than 0.5. From the analysis of nearly ...
  • Evidence for nonthermal radiation from the nuclei of Seyfert galaxies 
    Deshpande, M. R; Joshi, U. C (Astronomical Society of India, 1993)
    We report the detection of nonthermal radiation from the nuclei of four Seyfert galaxies through polarization studies. Our investigations on four galaxies (NGC 3081, NGC 4388, NGC 3227 and NGC 2992) show evidence of ...
  • On the nature of radiation from the nucleus of a CD galaxy A0779 
    Deshpande, M. R; Joshi, U. C (Astronomical Society of India, 1993)
    An attempt is made to detect synchrotron radiation from the nucleus of a CD galaxy A-0779 through polarization studies. We have detected a high degree of polarization (up to 9 percent in ultraviolet) with a bimodal ...
  • Starbursts triggered by central overpressure in interacting galaxies 
    Mousumi Das; Jog, C. J (Astronomical Society of India, 1993)
    We present a triggering mechanism for starbursts in the central regions of interacting galaxies. As a disk giant molecular cloud (GMC) falls into the central region of a galaxy following a galaxy encounter, it may be ...
  • Modelling rotation curves -- the turbulent way 
    Prabhu, R. D; Krishan, V (Astronomical Society of India, 1993)
    Helical hydrodynamic turbulence can magnify perturbation seed eddies and this can lead to the appearance of large scale structures. The evolution of the instability is accompanied by a transfer of energy from small scale ...
  • Testing the mechanisms for optical micro-variability of powerful active galactic nuclei 
    Gopal-Krishna; Sagar, R; Wiita, P. J (Astronomical Society of India, 1993)
    We present the first results of a new type of observational program being carried out using the 2.34m Vainu Bappu Telescope at Kavalur. This program involves intra-night optical monitoring of radio quiet but optically ...
  • Swing amplification in stars and gas: Origin of local spirit structure in galaxies 
    Jog, C. J (Astronomical Society of India, 1993)
    We present a study of the growth of local, non-axisymmetric perturbations in gravitationally coupled stars and gas in differentially rotating galactic disk. The amplified perturbations in stars and gas constitute trailing, ...
  • Straight arcs in gravitational lens systems 
    Narasimha, D; Chitre, S. M (Astronomical Society of India, 1993)
    Faint straight arcs extending over ten to twenty arcseconds have been observed behind rich clusters of galaxies elongated by the lensing action of the foreground cluster. When a cluster of galaxies has its projected surface ...
  • High resolution IRAS maps of spiral galaxies 
    Rengarajan, T. N; Ghosh, S. K; Verma, R. P (Astronomical Society of India, 1993)
    High resolution maps of nine spiral galaxies have been generated in the four IRAS bands using the High Resolution (HIRES) routine. These are used in conjunction with maps in H-alpha, CO, HI, radio continuum etc. to study ...
  • A gravitational lens probe of galaxy-scale dark matter? 
    Sunita Nair (Astronomical Society of India, 1993)
    We present a model for an observed gravitationally lensed system, MG2016+112. We assume that there are two galaxies acting as lenses (as suggested by the observations), each with a diffuse dark matter halo. It is shown ...
  • Sourceless Abelian gauge string in a Robertson-Walker universe with general spatial curvature 
    Bhattacharyya, D; Banerji, S (Astronomical Society of India, 1993)
    A model of sourceless Abelian gauge string was examined by J. R. Morris (1991) in a Robertson-Walker universe with a flat 3-space. We generalize this result to the case of positive or negative spatial curvatures. We find ...
  • Gravitational collapse of inhomogeneous dust: Naked singularities, black hole formation and Hawking evaporation 
    Unnikrishnan, C. S (Astronomical Society of India, 1993)
    There are several examples of existence of naked singularities in models of spherically symmetric gravitational collapse and they are considered to be counter-examples to the Cosmic Censorship (CCC). In fact, there were ...
  • On naked singularities in spherically symmetric gravitational collapse 
    Unnikrishnan, C. S (Astronomical Society of India, 1993)
    We explore the physical nature of the singularity which forms in the gravitational collapse of spherically symmetric pressureless dust with inhomogeneous density distribution (Tolman-Bondi model). We show that in this model ...
  • The origin of dark matter and its estimate in the metagalaxy 
    Srivastava, D. N (Astronomical Society of India, 1993)
    On dark matter, whereas current research is in the field of weakly interacting particles, this work puts forward a different line of approach. It interprets dark matter as a transformation of matter by a generalized ...
  • A maximum entropy method based scheme for the inversion of extended radio images in gravitationally lensed systems 
    Sunita Nair (Astronomical Society of India, 1993)
    A new scheme is advanced for the process of source reconstruction (or image inversion) from extended images in gravitationally lensed systems which show multiple imaging. We suggest that forward simulations of such systems ...
  • Computer simulation of cosmic ray trajectories in near earth space 
    Singh, R. K; Vahia, M. N; Durgaprasad, N (Astronomical Society of India, 1993)
    The dynamics of cosmic ray ions of energy 10-100 MeV/N in and around the terrestrial magnetic field is studied using the method of trajectory tracing. The trajectory of a cosmic ray particle is back traced from the point ...
  • Comparative study of diurnal anisotropy in CR intensity on quiet days and all days 
    Santosh Kumar; Gulati, U; Khare, D. K; Richharia, M. K (Astronomical Society of India, 1993)
    A comparative study of the diurnal variation of cosmic ray (CR) intensity has been performed on geomagnetically quiet days (QD) and all days (AD) using neutron monitor data for the year 1987. It is observed that even though ...

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