GRB 160410A: the first Chemical Study of the Interstellar Medium of a
  Short GRB
  Short Gamma-Ray Bursts (SGRBs) are produced by the coalescence of compact
binary systems which are remnants of massive stars. GRB 160410A is classified
as a short-duration GRB with extended emission and is currently the farthest
SGRB with a redshift determined from an afterglow spectrum and also one of the
brightest SGRBs to date. The fast reaction to the Neil Gehrels Swift
Observatory alert allowed us to obtain a spectrum of the afterglow using the
X-shooter spectrograph at the Very Large Telescope (VLT). The spectrum shows a
number of absorption features at a redshift of z=1.7177, in addition, we detect
two intervening systems at z=1.581 and z=1.444. The spectrum shows ly-alpha in
absorption with a column density of log N(HI)=21.3+/-0.3 cm$^{-2}$ which,
together with FeII, CII, SiII and OI, allow us to perform the first study of
chemical abundances in a SGRB host galaxy. We determine a metallicity of
[Fe/H]=-2.7+/-0.3, significantly lower than observed for any long GRB host. We
find no evidence for extinction in the afterglow spectral energy distribution
(SED). The environment has a low degree of ionisation and the CIV and SiIV
lines are completely absent. We do not detect an underlying host galaxy down to
deep limits. Additionally, we present the spectrum of GRB 201221D, another
high-z short GRB that shows absorption lines at z=1.045 but whose environment
seems to be more similar to the one of short GRBs as derived from the SED
fitting to the host photometry.
