Research Papers (JVN)

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Author: search.filters.author.Chitre, S. M.Subject: search.filters.subject.Quasars

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    3C 273 : A gravitationally lensed quasar?
    (EDP Sciences, 1984-05-30) Chitre, S. M.; Narasimha, D.; Narlikar, J. V.; et al.
    It is suggested that the abnormal brightness of the quasar 3C 273, coupled with the observations of superluminal motions in its radio core B as well as the misalignment of its VLBI jet with the optical jet, can be understood by postulating a faint spheroidal lensing galaxy located about halfway along the line of sight to the quasar. The lens model also helps to understand why the quasar is found slightly off-centre with respect to its nebulosity. The probability for such a lens system to arise for 3C 273 by chance is shown to be no less than that computed on the basis of the relativistic beaming hypothesis. Further tests of the lens model are discussed.
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    Faster-than-light motion in quasars
    (Indian Academy of Sciences, 1984-07-27) Narlikar, J. V.; Chitre, S. M.
    Over the past fifteen years, observations of some quasars with the techniques of very-long-baseline interferometry have shown that the angular separation between pairs of radio-emitting regions in their cores is increasing year after year. If the quasars are indeed as far away as implied by Hubble’s law, then these angular motions translate into linear speeds several times the speed of light. Several theoretical scenarios have been proposed to show that the observed motions are illusory. The leading contender in this field—the relativistic beam model—and an alternative offered by the concept of a gravitational screen are described and compared in the light of recent observational data.
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    Gravitational screens and superluminal separation in quasars
    (American Astronomical Society, 1980-01-15) Chitre, S. M.; Narlikar, J. V.
    The differential bending of radio waves by a suitably placed 'gravitational screen' such as an intervening galaxy can lead to large magnification of the separation velocity of the components in the nuclear region of a quasar. It is suggested that the apparent superluminal separation of such components observed in some quasars by the VLBI techniques could be due to velocity magnifications of this type. The astrophysical feasibility of this explanation is critically examined, and an optical search for objects of large mass-to-light ratio en route to quasars showing superluminal separation is advocated.