Failed Gamma-Ray Bursts: Thermal UV/Soft X-ray Emission Accompanied by Peculiar Afterglows

TL;DR

This paper proposes that 'failed' gamma-ray bursts with low Lorentz factors produce thermal UV/soft X-ray emissions from photospheres, lasting about a thousand seconds, with distinctive early afterglow features that can be observed by current satellites.

Contribution

It introduces the concept of failed GRBs with photospheric emissions outside internal shocks and describes their unique observational signatures.

Findings

Photospheric emission lasts ~1000 seconds with luminosity ~10^46 erg/s.

Failed GRBs have peculiar early afterglows distinguishable from normal GRBs.

Current and future satellites can detect these failed GRB events.

Abstract

We show that the photospheres of "failed" Gamma-Ray Bursts (GRBs), whose bulk Lorentz factors are much lower than 100, can be outside of internal shocks. The resulting radiation from the photospheres is thermal and bright in UV/Soft X-ray band. The photospheric emission lasts for about one thousand seconds with luminosity about several times 10^46 erg/s. These events can be observed by current and future satellites. It is also shown that the afterglows of failed GRBs are peculiar at the early stage, which makes it possible to distinguish failed GRBs from ordinary GRBs and beaming-induced orphan afterglows.