Discovery of a Transient Gamma-Ray Counterpart to FRB 131104

Abstract

We report our discovery in Swift satellite data of a transient gamma-ray counterpart (3.2σ confidence) to the fast radio burst FRB 131104, the first such counterpart to any FRB. The transient has duration T 90 ∼ > 100 s and fluence S γ ≈ 4 × 10 −6 erg cm −2 , increasing the energy budget for this event by more than a billion times; at the nominal z ≈ 0.55 redshift implied by its dispersion measure, the burst's gamma-ray energy output is E γ ≈ 5 × 10 51 erg. The observed radio to gamma-ray fluence ratio for FRB 131104 is consistent with a lower limit we derive from Swift observations of another FRB, which is not detected in gamma-rays, and with an upper limit previously derived for the brightest gamma-ray flare from SGR 1806−20, which was not detected in the radio. X-ray, ultraviolet, and optical observations beginning two days after the FRB do not reveal any associated afterglow, supernova, or transient; Swift observations exclude association with the brightest 65% of Swift gamma-ray burst X-ray afterglows, while leaving the possibility of an associated supernova at much more than 10% the FRB's nominal distance, D ∼ > 320 Mpc, largely unconstrained. Transient high-luminosity gamma-ray emission arises most naturally in a relativistic outflow or shock breakout, as for example from magnetar flares, gamma-ray bursts, relativistic supernovae, and some types of galactic nuclear activity. Our discovery thus bolsters the case for an extragalactic origin for some FRBs and suggests that future rapid-response observations might identify long-lived counterparts, resolving the nature of these mysterious phenomena and realizing their promise as probes of cosmology and fundamental physics.

Burst Astrophysics

“…The most intriguing result was obtained by J. J. DeLaunay, et al [25]. They report the discovery of a transient gamma-ray counterpart to the fast radio burst FRB 131104, the first such counterpart to any FRB.…”

“…They have modest energy in radio flash ( with gamma-ray energy that is more than 9 10 times greater, with dramatic implications for source models and a substantial improvement in the prospects for long-lived counterparts, including X-ray and radio afterglows [25].…”

A “Cosmic Comb” Model of Fast Radio Bursts

“…However, there might be γ-ray emission already 7 s before the FRB according to the data. Furthermore, the Swift BAT was not pointing toward the source direction before −7 s with respect to the FRB (DeLaunay et al 2016). So it is likely that the FRB occurred during the process of a long-duration GRB.…”

“…Models invoking more energetic magnetars as the source of FRBs have been proposed (Zhang 2014;Murase et al 2016;Piro 2016;Murase et al 2017;Gao & Zhang 2017;Dai et al 2016a;Metzger et al 2017). However, in order to account for both the repeater and the putative association of a GRB for FRB 131104 (DeLaunay et al 2016), both catastrophic and repeating mechanisms are needed.…”

“…The origin of fast radio bursts (FRBs) remains a mystery after one decade of observations (Lorimer et al 2007; Thornton et al 2013;Petroff et al 2015a;Champion et al 2016;Masui et al 2015;Keane et al 2016;Spitler et al 2016;DeLaunay et al 2016;Chatterjee et al 2017). The distance scale of FRBs is finally settled to the cosmological range (∼Gpc) thanks to multi-wavelength follow-up observations that nail down the host galaxy of the repeating source that produced FRB 121102 (Chatterjee et al 2017;Marcote et al 2017;Tendulkar et al 2017).…”