On the afterglow and progenitor of FRB 150418

TL;DR

This paper models the afterglow of FRB 150418 to constrain its energy and explores possible progenitor scenarios, including neutron star mergers and black hole mergers, with implications for gravitational wave associations.

Contribution

It provides the first detailed afterglow modeling of FRB 150418 and constrains its energy, ruling out many progenitor models while proposing two viable merger scenarios.

Findings

Isotropic energy of a few 10^{50} erg

Jet opening angle of ~0.22 rad

Potential GW/FRB/GRB associations

Abstract

Keane et al. recently detected a fading radio source following FRB 150418, leading to the identification of a putative host galaxy at $z = 0.492 \pm 0.008$. Assuming that the fading source is the afterglow of FRB 150418, I model the afterglow and constrain the isotropic energy of the explosion to be a few $10^{50}$ erg, comparable to that of a short duration GRB. The outflow may have a jet opening angle of $\sim 0.22$ rad, so that the beaming-corrected energy is below $10^{49}$ erg. The results rule out most FRB progenitor models for this FRB, but may be consistent with either of the following two scenarios. The first scenario invokes a merger of an NS-NS binary, which produced an undetected short GRB and a supra-massive neutron star, which subsequently collapsed into a black hole, probably 100s of seconds after the short GRB. The second scenario invokes a merger of a compact star binary (BH-BH, NS-NS, or BH-NS) system whose pre-merger dynamical magnetospheric activities made the FRB, which is followed by an undetected short GRB-like transient. The gravitational wave (GW) event GW150914 would be a sister of FRB 150418 in this second scenario. In both cases, one expects an exciting prospect of GW/FRB/GRB associations.