On the nature of the short duration GRB 050906

TL;DR

This paper investigates the nature of short GRB 050906 through deep optical and infrared observations, exploring potential progenitors like soft-gamma repeaters and merging compact objects, and analyzing its possible association with nearby galaxies.

Contribution

It provides the first deep optical/IR limits on GRB 050906 and discusses its potential origin from a soft-gamma repeater or a high-redshift event, considering its positional context.

Findings

No optical/IR afterglow detected to deep limits

Error circle includes a local starburst galaxy and a galaxy cluster at z=0.43

Constraints on progenitors based on optical signatures

Abstract

We present deep optical and infrared observations of the short duration GRB 050906. Although no X-ray or optical/IR afterglow was discovered to deep limits, the error circle of the GRB (as derived from the Swift BAT) is unusual incontaining the relatively local starburst galaxy IC328. This makes GRB 050906 a candidate burst from a soft-gamma repeater, similar to the giant flare from SGR 1806-20. The probability of chance alignment of a given BAT position with such a galaxy is small (<1%), although the size of the error circle (2.6 arcminute radius) is such that a higher-z origin can't be ruled out. Indeed, the error circle also includes a moderately rich galaxy cluster at z=0.43, which is a plausible location for the burst given the apparent preference that short GRBs have for regions of high mass density. No residual optical or infrared emission has been observed, either in the form of an afterglow or later time emission from any associated supernova-like event. We discuss the constraints these limits place on the progenitor of GRB 050906 based on the expected optical signatures from both SGRs and merging compact object systems.