• D. Narasimha

      Articles written in Journal of Astrophysics and Astronomy

    • Convective instability in the solar envelope

      D. Narasimha S. K. Pandey S. M. Chitre

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      The characteristics of the most unstable fundamental mode and the first harmonic excited in the convection zone of a variety of solar envelope models are shown to be in reasonable agreement with the observed features of granulation and supergranulation.

    • Straight Arc in abell 2390

      D. Narasimha S. M. Chitre

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      The straight arc in the galaxy-cluster Abell 2390 is investigated in the framework of a gravitational lens model that invokes a single background source galaxy. An extended source galaxy at a redshift of 0.913 is being marginally lensed by the foreground X-ray cluster of galaxies at a redshift of 0.231. It is demonstrated that a single lensed galaxy lying on or very near to the lip caustic of the cluster lens is capable of reproducing the linear morphology with the observed breaks.

    • Tracking the shadows through GMRT

      D. Narasimha N. Kanekar J. N. Chengalur

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      The structures of faint high redshift galaxies cannot be observed directly. But if a luminous quasar is located farther along their line of sight, high resolution absorption lines offer a valuable and reliable probe to their structure. GMRT is suited to monitor the absorption spectra, if the redshifted neutral hydrogen or OH doublet fall in one of the windows of the telescope. We present the OH doublet absorption spectra for the system B0218+357, taken at GMRT this year at resolution of approx. 9.5 km/sec with an rms noise of the order of 1 mJy. Based on our study of the OH doublet and 21cm neutral hydrogen line we infer that, in the lensing spiral galaxy of B0218 + 357, neutral hydrogen and OH coexist in tenous clouds and there is possibly a hole in the central part of the galaxy. In contrast, the gas is seen in high density clouds in the lens in an otherwise similar system PKS1830-211.

    • Explosive and Radio-Selected Transients: Transient Astronomy with Square Kilometre Array and its Precursors

      Poonam Chandra G. C. Anupama K. G. Arun Shabnam Iyyani Kuntal Misra D. Narasimha Alak Ray L. Resmi Subhashis Roy Firoza Sutaria

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      With the high sensitivity and wide-field coverage of the Square Kilometre Array (SKA), large samples of explosive transients are expected to be discovered. Radio wavelengths, especially in commensal survey mode, are particularly well-suited for uncovering the complex transient phenomena. This is because observations at radio wavelengths may suffer less obscuration than in other bands (e.g. optical/IR or X-rays) due to dust absorption. At the same time, multiwaveband information often provides critical source classification rapidly than possible with only radio band data. Therefore, multiwaveband observational efforts with wide fields of view will be the key to progress of transients astronomy from the middle 2020s offering unprecedented deep images and high spatial and spectral resolutions. Radio observations of Gamma Ray Bursts (GRBs) with SKA will uncover not only much fainter bursts and verifying claims of sensitivity-limited population versus intrinsically dim GRBs, they will also unravel the enigmatic population of orphan afterglows. The supernova rate problem caused by dust extinction in optical bands is expected to be lifted in the SKA era. In addition, the debate of single degenerate scenario versus double degenerate scenario will be put to rest for the progenitors of thermonuclear supernovae, since highly sensitive measurements will lead to very accurate mass loss estimation in these supernovae. One also expects to detect gravitationally lensed supernovae in far away Universe in the SKA bands. Radio counterparts of the gravitational waves are likely to become a reality once SKA comes online. In addition, SKA is likely to discover various new kinds of transients.

  • 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.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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