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  • Uncertainty principle limits on the cosmological constant 
    Sivaram, C (Springer, 1986-08)
    The identification of the cosmological constant term with the energy density of the vacuum enables lower and upper limits to be placed on its value. The upper limit arises from the constraint that the total zero-point ...
  • Understanding AGB Nucleosynthesis from Chemical Composition Studies of CH Stars 
    Drisya, K; Goswami, A (Astronomical Society of the Pacific, 2015-08)
    CH stars are known to show enhanced abundances of carbon and heavy s-process elements. They are metal-deficient population II objects. Their luminosities indicate that they are mostly giants; hence, the observed enhanced ...
  • Understanding galaxy mergers and AGN feedback with UVIT 
    Rubinur, K; Mousumi Das; Kharb, Preeti; Rahne, P. T (Cambridge University Press, 2021-01)
    Simulations expect an enhanced star-formation and active galactic nuclei (AGN) activity during galaxy mergers, which can lead to formation of binary/dual AGN. AGN feedback can enhance or suppress star-formation. We have ...
  • Understanding ghost interference 
    Qureshi, T; Pravabati, C; Shafaq, S (World Scientific Publishing Company, 2016-09)
    The ghost interference observed for entangled photons is theoretically analyzed using wave-packet dynamics. It is shown that ghost interference is a combined effect of virtual double-slit creation due to entanglement, and ...
  • Understanding jets from sources straddling the Fanaroff-Riley divide 
    Kharb, P; Stanley, E; Lister, M; Marshall, H; O'Dea, C; Baum, S (Cambridge University Press, 2015-03)
    Results from Chandra-HST-VLA observations of 13 hybrid sources are presented. Data from ten sources in the literature are analysed along with new data from three hybrid blazars belonging to the MOJAVE sample. Studies of ...
  • Understanding Li enhancement in K giants and role of accurate parallaxes 
    Raghubar Singh; Reddy, B. E (Cambridge University Press, 2018-07)
    Our recent studies based on a large sample of K giants with Hipparcos parallaxes and spectroscopic analysis resulted more than a dozen new Li-rich K giants including few super Lirich ones. Most of the Li-rich K giants ...
  • Understanding of Li production and its evolution in evolved stars 
    Singh, Raghubar (Indian Institute of Astrophysics, 2021-07)
    Lithium (Li) is susceptible to relatively low temperatures. Hence, Li abundances among red giants are expected to be depleted signi cantly, by a factor of 40-60, from its original value on the main sequence. Assuming A(Li)= ...
  • Understanding pulsar emission profiles from geometry and rotation effects 
    Thomas, R. M. C; Gupta, Y; Gangadhara, R. T (Astronomical Society of the Pacific, 2009-09)
    We have developed a method to locate the possible emission regions in pulsar magnetospheres, taking into account detailed effects of geometry and rotation of the neutron star. Using curvature radiation formulation, we ...
  • Understanding the behavior of energy X-rays from the black hole candidate GRS 1915+105 
    Nandi, A; Chakrabarti, S. K (Astronomical Society of India, 2002)
    Black Hole candidate GRS 1915+105 shows a very interesting behaviour at high energy X-rays. For instance, it shows quasi-Periodic Oscillations (QPO) only at high energies. Also the spectral slopes at high energies vary and ...
  • Understanding the effects of geometry and rotation on pulsar intensity profiles 
    Thomas, R. M. C; Gupta, Y; Gangadhara, R. T (Wiley-Blackwell, 2010-08-01)
    We have developed a method to compute the possible distribution of radio emission regions in a typical pulsar magnetosphere, taking into account the viewing geometry and rotational effects of the neutron star. Our method ...
  • Understanding the Radio Emission Geometry of Multiple-Component Radio Pulsars from Retardation and Aberration Effects 
    Gupta, Y; Gangadhara, R. T (The American Astronomical Society, 2003-02)
    We have conducted a detailed analysis of the emission geometry of a handful of radio pulsars that have prominent, multiple-component profiles at meter wavelengths. From careful determination of the total number of emission ...
  • Understanding the Radio Emission Geometry of PSR B0329+54 
    Gangadhara, R. T; Gupta, Y (American Astronomical Society, 2001-07)
    We have analyzed high-quality single-pulse data of PSR B0329+54 at 325 and 606 MHz to study the structure of the emission beam. Using the ``window-threshold technique,'' which is suitable for detecting weak emission ...
  • Understanding the secular evolution of NGC 628 using UltraViolet Imaging Telescope 
    Ujjwal, K; Kartha, Sreeja S; Subramanian, S; George, Koshy; Thomas, Robin; Mathew, Blesson (Oxford University Press on behalf of Royal Astronomical Society, 2022-10)
    Secular and environmental effects play a significant role in regulating the star-formation rate and hence the evolution of the galaxies. Since ultraviolet (UV) flux is a direct tracer of the star formation in galaxies, the ...
  • Unidentified molecular features in the red spectrum (5800 to 7300 Å) of PI Gruis 
    Murty, P. S (D.Reidel Publishing Co.,, 1982-11)
    Moderate dispersion (46 Å mm–1 at H) image-tube spectrum (5800–7300 Å) of the S star 1 Gru is found to exhibit several unidentified molecular features, in addition to the well-known bands of the oxides ofs-process elements. ...
  • Unidentified Sources in the FIRSSE Catalogue 
    Seal, P; Shivanandan, K (Astronomical Society of Indian, 1989-03)
    Thirty four sources are identified from 159 unidentified FIRSSE sources by matching the positions of the sources in different catalogues. Eighty three sources are examined optically on the POSS-E prints. We also discuss ...
  • Unified approach to photo- and electro-production of mesons with arbitrary spins 
    Ramachandran, G; Vidya, M. S; Balasubramanyam, J (Indian Academy of Sciences, 2007-01)
    A new approach to identify the independent amplitudes along with their partial wave multipole expansions, for photo- and electro-production is suggested, which is generally applicable to mesons with arbitrary ...
  • A unified description of anti-dynamo conditions for incompressible flows 
    Mangalam, A (Anita Publications, 2004-12)
    A general type of mathematical argument is described, which applies to all the cases in which dynamo maintenance of a steady magnetic field by motion in a uniform density is known to be impossible. Previous work has ...
  • A unified view on Aharanov-Bohm like phases and some applications 
    Unnikrishnan, C. S (Indian Academy of Sciences, 2001-03)
    The analysis of the Aharanov-Bohm phase and other similar physical effects in this paper is motivated by the philosophy that all physical changes, including phase changes, should originate in one of the local physical ...
  • The Unique Type Ib Supernova 2005bf: A WN Star Explosion Model for Peculiar Light Curves and Spectra 
    Tominaga, N; Tanaka, M; Nomoto, K; Mazzali, P. A; Deng, J; Maeda, K; Umeda, H; Modjaz, M; Hicken, M; Challis, P; Kirshner, R. P; Wood-Vasey, W. M; Blake, C. H; Bloom, J. S; Skrutskie, M. F; Szentgyorgyi, A; Falco, E. E; Inada, N; Minezaki, T; Yoshii, Y; Kawabata, K; Iye, M; Anupama, G. C; Sahu, D. K; Prabhu, T. P (The American Astronomical Society, 2005-11-10)
    Observations and modeling for the light curve (LC) and spectra of supernova (SN) 2005bf are reported. This SN showed unique features: the LC had two maxima, and declined rapidly after the second maximum, while the spectra ...
  • Universality of charge arising from torsion 
    de Sabbata, V; Sivaram, C (Springer, 1993-04)
    We show that in relating torsion to intrinsic unit of spin h, with the consideration that defects in spacetime topology occur in multiples of Planck length, the electric charge appears as a derived concept, showing its ...

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