LIMITS ON FAST RADIO BURSTS FROM FOUR YEARS OF THE V-FASTR EXPERIMENT

ABSTRACT 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 rede...

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Bibliographic Details
Published in:The Astrophysical journal 2016-08, Vol.826 (2), p.223
Main Authors: Burke-Spolaor, S., Trott, Cathryn M., Brisken, Walter F., Deller, Adam T., Majid, Walid A., Palaniswamy, Divya, Thompson, David R., Tingay, Steven J., Wagstaff, Kiri L., Wayth, Randall B.
Format: Article
Language:English
Subjects:
ABSORPTION
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
DETECTION
DISPERSIONS
DISTRIBUTION
FREQUENCY DEPENDENCE
GALAXIES
PULSARS
pulsars: general
radio continuum: general
SPECTRA
WAVELENGTHS
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Summary:ABSTRACT 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 allows direct comparison with the 20 cm Parkes rate, and we derive a power-law limit of (95% confidence limit) on the index of FRB source counts, . Using the previously measured FRB rate and the unprecedented amount of survey time spent searching for FRBs at a large range of wavelengths ( cm), we also place frequency-dependent limits on the spectral distribution of FRBs. The most constraining frequencies place two-point spectral index limits of and , where fluence if we assume that the burst rate reported by Champion et al. of is accurate (for bursts of ∼3 ms duration). This upper limit on 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.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/826/2/223