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Limits on Fast Radio Bursts from Four Years of the V-FASTR Experiment

Burke-Spolaor, S. and Trott, Cathryn M. and Brisken, Walter F. and Deller, Adam T. and Majid, Walid A. and Palaniswamy, Divya and Thompson, David R. and Tingay, Steven J. and Wagstaff, Kiri L. and Wayth, Randall B. (2016) Limits on Fast Radio Bursts from Four Years of the V-FASTR Experiment. Astrophysical Journal, 826 (2). Art. No. 223. ISSN 0004-637X.

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The V-FASTR experiment on the Very Long Baseline Array was designed to detect dispersed pulses of milliseconds in duration, such as fast radio bursts (FRBs). We use all V-FASTR data through 2015 February to report V-FASTR's upper limits on the rates of FRBs, and compare these with rederived rates from Parkes FRB detection experiments. V-FASTR's operation at λ = 20,cm allows direct comparison with the 20 cm Parkes rate, and we derive a power-law limit of y < -0.4 (95% confidence limit) on the index of FRB source counts, N(>S)∝ S^y. Using the previously measured FRB rate and the unprecedented amount of survey time spent searching for FRBs at a large range of wavelengths (0.3 cm > λ > 90 cm), we also place frequency-dependent limits on the spectral distribution of FRBs. The most constraining frequencies place two-point spectral index limits of ɑ^(4cm)_(20cm) and ɑ_(90cm)^(20cm) > -7.6, where fluence F ∝ ƒ^ɑ if we assume that the burst rate reported by Champion et al. of R(F ~ 0.6Jy ms) = 7 x 10^3 sky^(-1) is accurate (for bursts of ~3 ms duration). This upper limit on α suggests that if FRBs are extragalactic but noncosmological, on average they are not experiencing excessive free–free absorption due to a medium with high optical depth (assuming temperature ~8000 K), which excessively inverts their low-frequency spectrum. This in turn implies that the dispersion of FRBs arises in either or both of the intergalactic medium or the host galaxy, rather than from the source itself.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Burke-Spolaor, S.0000-0003-4052-7838
Deller, Adam T.0000-0001-9434-3837
Majid, Walid A.0000-0002-4694-4221
Thompson, David R.0000-0003-1100-7550
Additional Information:© 2016 American Astronomical Society. Received 2015 June 24; revised 2016 May 18; accepted 2016 May 18; published 2016 August 2. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We acknowledge the exellent commentary by two referees and the ApJ statistician on the paper's manuscripts. This work was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. C.M.T. is supported by an Australian Research Council DECRA Fellowship through project number DE140100316.
Funding AgencyGrant Number
Australian Research CouncilCE110001020
Australian Research CouncilDE140100316
Subject Keywords:pulsars: general; radio continuum: general
Issue or Number:2
Record Number:CaltechAUTHORS:20161003-082800319
Persistent URL:
Official Citation:S. Burke-Spolaor et al 2016 ApJ 826 223
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70743
Deposited By: Ruth Sustaita
Deposited On:03 Oct 2016 17:16
Last Modified:09 Mar 2020 13:18

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