Jayaram N. Chengalur
Articles written in Journal of Astrophysics and Astronomy
Volume 22 Issue 1 March 2001 pp 35-50
GMRT observations of interstellar clouds in the 21cm line of atomic hydrogen
Rekhesh Mohan K. S. Dwarakanath G. Srinivasan Jayaram N. Chengalur
Nearby interstellar clouds with high (|ν|≥10km s−1) random velocities although easily detected in NaI and CaII lines have hitherto not been detected (in emission or absorption) in the HI 21cm line. We describe here deep Giant Metrewave Radio Telescope (GMRT) HI absorption observations toward radio sources with small angular separation from bright O and B stars whose spectra reveal the presence of intervening high random velocity CaII absorbing clouds. In 5 out of the 14 directions searched we detect HI 21cm absorption features from these clouds. The mean optical depth of these detections is ∼0.09 and FWHM is ∼10km s−1, consistent with absorption arising from CNM clouds.
Volume 38 Issue 1 March 2017 Article ID 0009 Special Section on "The Ooty Wide Field Array"
Jayaram N. Chengalur Somnath Bharadwaj
Volume 38 Issue 1 March 2017 Article ID 0010 Review Article
C. R. Subrahmanya P. K. Manoharan Jayaram N. Chengalur
We describe here an ongoing upgrade to the legacy Ooty Radio Telescope (ORT). The ORT is a cylindrical parabolic cylinder 530 m × 30 m in size operating at a frequency of 326.5 (or $z \sim 3.35$ for the HI 21-cm line). The telescope has been constructed on a North–South hill slope whose gradient is equal to the latitude of the hill, making it effectively equatorially mounted. The feed consists of an array of 1056 dipoles. The key feature of this upgrade is the digitization and cross-correlation of the signals of every set of 4-dipoles. This converts the ORT into a 264 element interferometer with a field-of-view of $ 2^{\circ} \times 27.4^{\circ} \cos(\delta)$. This upgraded instrument is called the Ooty Wide Field Array (OWFA). This paper briefly describes the salient features of the upgrade, as well as its main science drivers. There are three main science drivers viz. (1) observations of the large scale distribution of HI in the post-reionization era, (2) studies of the propagation of plasma irregularities through the inner heliosphere and (3) blind surveys for transient sources. More details on the upgrade, as well as on the expected science uses can be found in other papers in this special issue.
Volume 38 Issue 1 March 2017 Article ID 0017 Review Article
FRB Event Rate Predictions for the Ooty Wide Field Array
Siddhartha Bhattacharyya Apurba Bera Somnath Bharadwaj N. D. Ramesh Bhat Jayaram N. Chengalur
We developed a generic formalism to estimate the event rate and the redshift distribution of Fast Radio Bursts (FRBs) in our previous publication (Bera
Volume 43, 2022
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