The first interferometric detections of fast radio bursts

Abstract

We present the first interferometric detections of Fast Radio Bursts (FRBs), an enigmatic new class of astrophysical transient. In a 180-day survey of the Southern sky we discovered 3 FRBs at 843 MHz with the UTMOST array, as part of commissioning science during a major ongoing upgrade. The wide field of view of UTMOST (≈ 9 deg 2 ) is well suited to FRB searches. The primary beam is covered by 352 partially overlapping fan-beams, each of which is searched for FRBs in real time with pulse widths in the range 0.655 to 42 ms, and dispersion measures ≤2000 pc cm −3 . Detections of FRBs with the UTMOST array places a lower limit on their distances of ≈ 10 4 km (limit of the telescope near-field) supporting the case for an astronomical origin. Repeating FRBs at UTMOST or an FRB detected simultaneously with the Parkes radio telescope and UTMOST, would allow a few arcsec localisation, thereby providing an excellent means of identifying FRB host galaxies, if present. Up to 100 hours of follow-up for each FRB has been carried out with the UTMOST, with no repeating bursts seen. From the detected position, we present 3σ error ellipses of 15 × 8.4 • on the sky for the point of origin for the FRBs. We estimate an all-sky FRB rate at 843 MHz above a fluence F lim of 11 Jy ms of ∼ 78 events sky −1 d −1 at the 95 percent confidence level. The measured rate of FRBs at 843 MHz is of order two times higher than we had expected, scaling from the FRB rate at the Parkes radio telescope, assuming that FRBs have a flat spectral index and a uniform distribution in Euclidean space (Caleb et al. 2016b). We examine how this can be explained by FRBs having a steeper spectral index and/or a flatter logN -logF distribution than expected for a Euclidean Universe.

A Fast Radio Burst Search Method for VLBI Observation

“…Keane & Petroff (2015) report an FRB event rate of 2500 events per sky per day above a 1.4 GHz fluence of 2 Jy ms. If we adopt an FRB spectral index γ of 0.0 and a fluence index α of -1.0 as discussed in Caleb et al (2017), the FRB detection rate for VGOS baseline with a fluence limit of 5.3 Jy ms at 2.2 GHz is 0.0076 event per day. We have to point out that above estimation is conservative.…”

The Dispersion of Fast Radio Bursts from a Structured Intergalactic Medium at Redshifts z < 1.5

“…); #23 -#25 (Caleb et al 2017). Column 5 gives the IGM dispersion, after subtracting contributions from the Milky Way Galaxy (column 4) and FRB host galaxy (constant 100 cm −3 pc).…”

Probing Motion of Fast Radio Burst Sources by Timing Strongly Lensed Repeaters

“…Note that the signal-to-noise ratio depends on both the fluence  and de-dispersed pulse width τ as  t µ -S N 1 2 . Given the fact that many bursts with duration ∼10 ms have been detected (e.g., Champion et al 2016;Caleb et al 2017b), further broadening by a factor of ∼10 (to 10 ms 2 ) will decrease S N by a factor of ∼3 (the fluence is unchanged). Future telescopes may be a factor of a few more sensitive than current ones.…”

“…In particular, a repeating source, if lensed, will result in a set of multiple bursts for each repetition. With the prospect that forthcoming large-scale radio surveys, including UTMOST (Caleb et al 2017a), HIRAX (Newburgh et al 2016), CHIME (Bandura et al 2014), and later on SKA1 (Macquart et al 2015), will have the capacity to find~-10 10 the interesting situation of a strongly lensed FRB repeater becomes worthy of consideration.…”