GRB171010A / SN2017htp: a GRB-SN at z=0.33

TL;DR

This paper reports a new case of a gamma-ray burst (GRB) at redshift 0.33 linked with a supernova, providing insights into the properties of such events at higher distances and their host galaxy environments.

Contribution

It presents detailed spectroscopic observations of a GRB-SN at z=0.33, expanding the known sample and characterizing the supernova's properties and host galaxy environment at higher redshift.

Findings

Supernova similar to SN 1998bw with Ni mass of 0.33 M_sun.

Ejected mass of 4.1 M_sun and kinetic energy of 8.1 x 10^{51} erg.

GRB progenitor located in a bright HII region with SFR ~0.2 M_sun/yr.

Abstract

The number of supernovae known to be connected with long-duration gamma-ray bursts is increasing and the link between these events is no longer exclusively found at low redshift ($z \lesssim 0.3$) but is well established also at larger distances. We present a new case of such a liaison at $z = 0.33$ between GRB\,171010A and SN\,2017htp. It is the second closest GRB with an associated supernova of only three events detected by Fermi-LAT. The supernova is one of the few higher redshift cases where spectroscopic observations were possible and shows spectral similarities with the well-studied SN\,1998bw, having produced a similar Ni mass ($M_{\rm Ni}=0.33\pm0.02 ~\rm{M_{\odot}}$) with slightly lower ejected mass ($M_{\rm ej}=4.1\pm0.7~\rm{M_{\odot}}$) and kinetic energy ($E_{\rm K} = 8.1\pm2.5 \times 10^{51} ~\rm{erg}$). The host-galaxy is bigger in size than typical GRB host galaxies, but the analysis of the region hosting the GRB revealed spectral properties typically observed in GRB hosts and showed that the progenitor of this event was located in a very bright HII region of its face-on host galaxy, at a projected distance of $\sim$ 10 kpc from its galactic centre. The star-formation rate (SFR$_{GRB} \sim$ 0.2 M$_{\odot}$~yr$^{-1}$) and metallicity (12 + log(O/H) $\sim 8.15 \pm 0.10$) of the GRB star-forming region are consistent with those of the host galaxies of previously studied GRB-SN systems.