Contamination of short GRBs by giant magnetar flares: Significance of downward revision in distance to SGR 1806-20

TL;DR

Revising the distance to SGR 1806-20 clarifies the contamination level of short GRBs by magnetar flares, impacting our understanding of their origins and frequency.

Contribution

This paper demonstrates how a revised distance measurement to SGR 1806-20 resolves previous discrepancies in magnetar flare contamination estimates in short GRBs.

Findings

Revised distance to SGR 1806-20 aligns contamination estimates with observed data.

Magnetar progenitor masses vary significantly, from ~17 to ~50 solar masses.

Contamination of short GRBs by magnetar flares is consistent with current flare frequency estimates.

Abstract

We highlight how the downward revision in the distance to the star cluster associated with SGR 1806-20 by Bibby et al. reconciles the apparent low contamination of BATSE short GRBs by intense flares from extragalactic magnetars without recourse to modifying the frequency of one such flare per 30 years per Milky Way galaxy. We also discuss the variety in progenitor initial masses of magnetars based upon cluster ages, ranging from ~50 Msun for SGR 1806-20 and iAXP CXOU J164710.2-455216 Westerlund 1 to ~17 Msun for SGR 1900+14 according to Davies et al. and presumably also 1E 1841-045 if it originated from one of the massive RSG clusters #2 or #3.