• Volume 6, Issue 2

      June 1985,   pages  77-112

    • Spectroscopic binaries near the North Galactic pole - Paper 12:6 Boötis

      R. F. Griffin

      More Details Abstract Fulltext PDF

      Photoelectric radial-velocity measurements show that 6 Boötis undergoes small periodic variations of velocity. An orbit with a 2.6-year period and a semi-amplitude of little more than 1 km s-1 is derived. The amplitude is smaller by a factor of two than that of any plausible orbit previously derived from radial velocities.

    • Energetics of the Kerr-Newman black hole by the penrose process

      Manjiri Bhat Sanjeev Dhurandhar Naresh Dadhich

      More Details Abstract Fulltext PDF

      We have studied in detail the energetics of Kerr-Newman black hole by the Penrose process using charged particles. It turns out that the presence of electromagnetic field offers very favourable conditions for energy extraction by allowing for a region with enlarged negative energy states much beyondr = 2M, and higher negative values for energy. However, when uncharged particles are involved, the efficiency of the process (defined as the gain in energy/input energy) gets reduced by the presence of charge on the black hole in comparison with the maximum efficiency limit of 20.7 per cent for the Kerr black hole. This fact is overwhelmingly compensated when charged particles are involved as there exists virtually no upper bound on the efficiency. A specific example of over 100 per cent efficiency is given.

    • Observations of hydrogen deficient binary Upsilon sagittarii

      N. Kameswara Rao V. R. Venugopal

      More Details Abstract Fulltext PDF

      The absolute magnitudeMv of the hydrogen deficient binary υ Sgr has been estimated as -4.8 ± 1.0 from the distribution of the interstellar reddening, polarization and interstellar lines of the surrounding stars. From the ANS observations obtained at the time of the secondary eclipse, it appears that the hotter secondary is surrounded by a disc with colours of a B8-B9 star. The λ 1550 CIv absorption line arising in the stellar wind does not show any change in strength during the secondary minimum. The upper limit to the mass-loss rate from the high temperature wind is estimated as ≤ 5 × 10-7 M⊙ yr-1 from the 2 cm and 6 cm radio observations.

  • 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.

© 2017-2019 Indian Academy of Sciences, Bengaluru.