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

Abstract

We highlight how the downward revision in the distance to the star cluster associated with SGR 1806-20 by Bibby et al. (2008) 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 M for SGR 1806-20 and AXP CXOU J164710.2-455216 in Westerlund 1 to $17 M for SGR 1900+14 according to Davies et al. (2009) and presumably also 1E 1841-045 if it originated from one of the massive RSG clusters #2 or #3.

Magnetars: the physics behind observations. A review

“…However, as already noted by Popov & Stern (2006), this prediction may be too optimistic, since no evidence has been found for an excess of BATSE short GRBs from the direction of M82, M83, NGC253 and NGC4945, nor from the Virgo cluster (Palmer et al, 2005). Similarly, negative results have been reported by Lazzati et al (2005); Tanvir et al (2005), and overall these studies suggest that no more than a few percent, maybe up to ∼ 8% of the short GRBs seen by BATSE could be giant flares from extragalactic SGRs (see also Hurley et al, 2005;Crowther et al, 2011;Svinkin et al, 2015, the latter for a recent update on the detection upper limits).…”