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A GMRT 150 MHz search for variables and transients in Stripe 82

Hajela, A. and Mooley, K. P. and Intema, H. T. and Frail, D. A. (2019) A GMRT 150 MHz search for variables and transients in Stripe 82. Monthly Notices of the Royal Astronomical Society, 490 (4). pp. 4898-4906. ISSN 0035-8711. doi:10.1093/mnras/stz2918.

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We have carried out a dedicated transient survey of 300 deg2 of the SDSS Stripe 82 region using the Giant Metrewave Radio Telescope (GMRT) at 150 MHz. Our multi-epoch observations, together with the TGSS survey, allow us to probe variability and transient activity on four different time-scales, beginning with 4 h and up to 4 yr. Data calibration, RFI flagging, source finding, and transient search were carried out in a semi-automated pipeline incorporating the SPAM recipe. This has enabled us to produce superior-quality images and carry out reliable transient search over the entire survey region in under 48 h post-observation. Among the few thousand unique point sources found in our 5σ single-epoch catalogues (flux density thresholds of about 24, 20, 16, and 18 mJy on the respective time-scales), we find <0.08 per cent, 0.01 per cent, <0.06 per cent, and 0.05 per cent to be variable (beyond a significance of 4σ and fractional variability of 30 per cent) on time-scales of 4 h, 1 d, 1 month, and 4 yr, respectively. This is substantially lower than that in the GHz sky, where ∼1 per cent of the persistent point sources are found to be variable. Although our survey was designed to probe a superior part of the transient phase space, our transient search did not yield any significant candidates. The transient (preferentially extragalactic) rate at 150 MHz is therefore <0.005 on time-scales of 1 month and 4 yr, and <0.002 on time-scales of 1 d and 4 h, beyond 7σ detection threshold. We put these results in perspective with the previous studies and give recommendations for future low-frequency transient surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Mooley, K. P.0000-0002-2557-5180
Intema, H. T.0000-0002-5880-2730
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 October 3. Received 2019 September 23; in original form 2019 May 23. AH acknowledges support from the 2018 NRAO summer research program, where the majority of the analysis was done. KPM is a Jansky Fellow of the NRAO. Thanks to Nimisha Kantharia, Preshanth Jagannathan and Gregg Hallinan, who provided help with the GMRT proposal and observing. We thank the staff of the GMRT who have made these observations possible. The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. We thank the anonymous referee for helpful comments on the manuscript.
Funding AgencyGrant Number
National Radio Astronomy ObservatoryUNSPECIFIED
Jansky FellowshipUNSPECIFIED
Subject Keywords:catalogues, surveys, stars: activity, galaxies: active, radio continuum: galaxies
Issue or Number:4
Record Number:CaltechAUTHORS:20200109-143244190
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Official Citation:A Hajela, K P Mooley, H T Intema, D A Frail, A GMRT 150 MHz search for variables and transients in Stripe 82, Monthly Notices of the Royal Astronomical Society, Volume 490, Issue 4, December 2019, Pages 4898–4906,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100612
Deposited By: George Porter
Deposited On:10 Jan 2020 16:26
Last Modified:16 Nov 2021 17:55

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