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tokens: to the general population of XRT light curves of GRBs. The gray shaded region is a compilation of long GRB light curves ( Evans et al. 2007 , 2009 ), where the color represents density. The light blue lines are sGRB light curves from bursts with duration of T 90 ≲ 2 s and those that were classified as short in Kann et al. (2011) , Berger (2014) and D’Avanzo et al. (2014) . The thick green line is GRB 111117A. Despite the remarkably high redshift, the luminosity is comparable to the bulk of the short burst population, and subluminous compared to the lGRB population. The inset shows the X-ray luminosity distributions of sGRBs and lGRBs at 10 ks, indicated by the vertical dashed line in the main panel. The separation of GRBs in two distinct classes based on their high-energy observables points to an intrinsically different physical origin. Long GRBs are typically interpreted as collapsars ( MacFadyen Woosley 1999 ) in which a single, massive star undergoes gravitational collapse, where the currently preferred model for sGRBs is the merger of two NSs ( Eichler et al. 1989 ; Nakar 2007 ). Bromberg et al. (2013) investigated the degree to which high-energy observables of the long and short GRB populations overlap, and quantified the certainty in class membership. According to Bromberg et al. (2013) , GRB 111117A has a probability of being a sGRB. Compared to two other sGRB candidates at high redshift, GRB 060121 ( T 90 = 1.97 ± 0.06 s; de Ugarte Postigo et al. 2006 ; Levan et al. 2006 ) at 1.7 ≲ z ≲ 4.5 () and GRB 090426 ( T 90 = 1.28 ± 0.09 s; Antonelli et al. 2009 ; Levesque et al. 2010 ; Thöne et al. 2011 ) at z = 2.609 (), the certainty in class membership for GRB 111117A is much higher. Additionally, Horváth et al. (2010) classify both GRB 060121 and GRB 090426 as intermediate-duration bursts because both events have very soft spectra, compared to the hard ones typically seen in sGRBs. Intermediate bursts are very clearly related in their properties to lGRBs ( de Ugarte Postigo et al. 2011 ), so they are unlikely to come from compact object mergers. GRB 111117A is also securely classified as a sGRB according to the Horváth et al. (2010) classification scheme. A number of other GRBs are thought to be short and at relatively high redshift ( z ≳ 0.9). If we consider bursts with a probability of being short f NC > 50%, according to the Bromberg et al. (2013) classification scheme, five sGRB are found: GRB 051210 at z ~ 1.3 ( f NC = ; Leibler Berger 2010 ), GRB 060801 at z = 1.131 ( f NC = ; Berger et al. 2007 ), GRB 070714 at z = 0.923 (no f NC due to extended emission; Graham et al. 2009 ), GRB 090510 at z = 0.903 ( f NC = ; McBreen et al. 2010 ), and GRB 100117 at z = 0.915 ( f NC = ; Fong et al. 2011 ). Although in individual cases a secure host association (hence redshift determination) is uncertain, there does seem to be a number of sGRBs at z ~ 1. This certainly makes GRB 111117A, by far, the highest redshift sGRB detected to date. The