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New Limits on the Low-frequency Radio Transient Sky Using 31 hr of All-sky Data with the OVRO-LWA

Anderson, Marin M. and Hallinan, Gregg and Eastwood, Michael W. and Monroe, Ryan M. and Callister, Thomas A. and Dowell, Jayce and Hicks, Brian and Huang, Yuping and Kassim, Namir E. and Kocz, Jonathon and Lazio, T. Joseph W. and Price, Danny C. and Schinzel, Frank K. and Taylor, Greg B. (2019) New Limits on the Low-frequency Radio Transient Sky Using 31 hr of All-sky Data with the OVRO-LWA. Astrophysical Journal, 886 (2). Art. No. 123. ISSN 1538-4357. doi:10.3847/1538-4357/ab4f87.

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We present the results of the first transient survey from the Owens Valley Radio Observatory Long Wavelength Array (OVRO–LWA) using 31 hr of data, in which we place the most constraining limits on the instantaneous transient surface density at timescales of 13 s to a few minutes and at frequencies below 100 MHz. The OVRO–LWA is a dipole array that images the entire viewable hemisphere with 58 MHz of bandwidth from 27 to 84 MHz at 13 s cadence. No transients are detected above a 6.5σ flux density limit of 10.5 Jy, implying an upper limit to the transient surface density of 2.5 × 10⁻⁸ deg⁻² at the shortest timescales probed, which is orders of magnitude deeper than has been achieved at sub-100 MHz frequencies and comparable flux densities to date. The nondetection of transients in the OVRO–LWA survey, particularly at minutes-long timescales, allows us to place further constraints on the rate of the potential population of transients uncovered by Stewart et al. From their transient rate, we expect a detection of 8.4^(+31.8)_(-8.0) events, and the probability of our null detection is 1.9^(+644)_(-1.9) x 10⁻³, ruling out a transient rate >1.4 × 10⁻⁴ days⁻¹ deg⁻² with 95% confidence at a flux density limit of 18.1 Jy, under the assumption of a flat spectrum and wide bandwidth. We discuss the implications of our nondetection for this population and further constraints that can be made on the source spectral index, intrinsic emission bandwidth, and resulting luminosity distribution.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Anderson, Marin M.0000-0003-2238-2698
Hallinan, Gregg0000-0002-7083-4049
Eastwood, Michael W.0000-0002-4731-6083
Callister, Thomas A.0000-0001-9892-177X
Dowell, Jayce0000-0003-1407-0141
Huang, Yuping0000-0003-4267-6108
Kassim, Namir E.0000-0001-8035-4906
Kocz, Jonathon0000-0003-0249-7586
Lazio, T. Joseph W.0000-0002-3873-5497
Price, Danny C.0000-0003-2783-1608
Schinzel, Frank K.0000-0001-6672-128X
Taylor, Greg B.0000-0001-6495-7731
Additional Information:© 2019 The American Astronomical Society. Received 2019 February 25; revised 2019 October 3; accepted 2019 October 18; published 2019 November 28. The authors thank the anonymous referee for useful and constructive comments that helped us to improve the original text of this paper. This material is based in part upon work supported by the National Science Foundation under Grant AST-1654815 and AST-1212226. G.H. acknowledges the support of the Alfred P. Sloan Foundation and the Research Corporation for Science Advancement. The OVRO–LWA project was initiated through the kind donation of Deborah Castleman and Harold Rosen. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration, including partial funding through the President's and Director's Fund Program. Software: CASA (McMullin et al. 2007), TTCal calibration software package for the OVRO–LWA (Eastwood 2016), WSClean (Offringa et al. 2014b), Scipy (Jones et al. 2001).
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Research CorporationUNSPECIFIED
JPL President and Director's FundUNSPECIFIED
Subject Keywords:Radio transient sources; Radio interferometry; Non-thermal radiation sources; Radio astronomy
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Radio transient sources (2008); Radio interferometry (1346); Non-thermal radiation sources (1119); Radio astronomy (1338)
Record Number:CaltechAUTHORS:20191119-092021675
Persistent URL:
Official Citation:Marin M. Anderson et al 2019 ApJ 886 123
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99924
Deposited By: Tony Diaz
Deposited On:19 Nov 2019 19:09
Last Modified:16 Nov 2021 17:50

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