A "kilonova" associated with short-duration gamma-ray burst 130603B

TL;DR

This paper presents strong evidence for a kilonova associated with short gamma-ray burst 130603B, supporting the neutron star merger origin of SGRBs and their role in heavy element production.

Contribution

It provides the first direct observational evidence linking kilonovae to short gamma-ray bursts, confirming theoretical predictions.

Findings

Detection of near-infrared transient consistent with a kilonova

Supports neutron star merger as origin of SGRBs

Indicates kilonovae as sites of r-process element synthesis

Abstract

Short-duration gamma-ray bursts (SGRBs) are intense flashes of cosmic gamma-rays, lasting less than ~2 s, whose origin is one of the great unsolved questions of astrophysics today. While the favoured hypothesis for their production, a relativistic jet created by the merger of two compact stellar objects (specifically, two neutron stars, NS-NS, or a neutron star and a black hole, NS-BH), is supported by indirect evidence such as their host galaxy properties, unambiguous confirmation of the model is still lacking. Mergers of this kind are also expected to create significant quantities of neutron-rich radioactive species, whose decay should result in a faint transient in the days following the burst, a so-called "kilonova". Indeed, it is speculated that this mechanism may be the predominant source of stable r-process elements in the Universe. Recent calculations suggest much of the kilonova energy should appear in the near-infrared (nIR) due to the high optical opacity created by these heavy r-process elements. Here we report strong evidence for such an event accompanying SGRB 130603B. If this simplest interpretation of the data is correct, it provides (i) support for the compact object merger hypothesis of SGRBs, (ii) confirmation that such mergers are likely sites of significant r-process production and (iii) quite possibly an alternative, un-beamed electromagnetic signature of the most promising sources for direct detection of gravitational waves.