• N. C. Rana

      Articles written in Journal of Astrophysics and Astronomy

    • A note on the self-consistency of the EIH equations of motion

      Rajat Roy N. C. Rana

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      The self-consistency of the Einstein Infeld and Hoffman (EIH) equations of motion is critically examined in the limiting case of a threebody problem where two bodies are very close to each other and a third quite far removed from them

    • Chemical evolution of the high redshift galaxies

      Pushpa Khare N. C. Rana

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      We have tried to determine the rate of chemical evolution of high redshift galaxies from the observed redshift distribution of the heavy element absorption systems in the spectra of QSOs, taking into account the evolution in the intensity of the metagalactic UV ionizing radiation background, the radius and/or the co-moving number density of, and the fraction of mass in the form of gas in, the absorbers. The data for both the Lyman limit systems and the C IV systems have been fitted simultaneously. It seems that the abundance of carbon has possibly increased by about a factor of 5 to 20 from the cosmic time corresponding to the redshift ≃ 4 to 2. The data also suggest that either the radius or the co-moving number density of the galaxies increased with redshift up to z = 2.0 and decreased slowly thereafter. The total mass of the halo gas was higher in the past, almost equal to the entire mass of the galaxy at z = 4. The hydrogen column density distribution for Lyman limit systems predicted by the model is in agreement with the observed distribution.

    • Test of evolutionary models for stellar population studies

      N. Srivastva R. K. Gulati N. C. Rana

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      Using the Andersen (1991) data on the mass, absolute visual magnitude, the effective surface temperature and the bolometric corrections, new calibrations for the mass vs. absolute visual magnitude and for the bolometric correction vs. effective surface temperature have been derived. Comparison between the latest evolutionary models with the empirical data has been made to test the evolutionary models for the purpose of stellar population studies.

    • Mass luminosity ratio of nearby stars and its relation to Baryonic dark matter problem

      N. C. Rana Mridula Chandola

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      In view of the recent report on the discovery of low mass halo stars for the candidates of MACHOs, a calculation has been made for the possible enhancement ofM/L ratio for populations of stars of varying mass domains taking the input data from the latest present day mass function (PDMF) of stars. It is seen that there is good scope for explaining dark matter problem where the dark matter is mostly in the form of low mass stars.

    • Metallicity distribution of F-dwarf stars in the solar neighbourhood

      N. C. Rana Atish D. Jana

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      A volume-limited sample of F-dwarfs is chosen from Knude (1989) with low radial velocity as well as distance from the sun and compared with the expected model metallicity [Fe/H] distributions, taking the possible chemical inhomogeneity into account. There is found to be an agreement between the two within the error limits of small sampling.

  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

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