Explosive transients, their origins and their use to study the high-redshift Universe

Abstract:
Explosive transients are usually connected to massive stars, directly or indirectly. Some of the most luminous of those explosions are gamma-ray bursts (GRBs) and superluminous supernovae (SLSNe). GRBs come in two different classes, long GRBs whose progenitors are massive stars with low metallicity and high rotation rate, and short GRBs, the merger of two compact objects and one of the known sources of gravitational wave signals. Type I SLSNe (without H in their spectra) were first thought to have progenitors similar to long GRBs, but studies of the host galaxies have suggested more extreme stars for those events. Due to their rare numbers and the fact that they are hosted mostly in dwarf galaxies we will likely not be able to observe the progenitor systems of any of these events before explosion in the near future. In this talk I will review what we know about the progenitors of different stellar explosions and how we use the host galaxy and environment to get indirect information on the progenitor, in particular using 3D spectroscopy. One important aspect is where the star-formation originates giving rise to the progenitors and I will focus on a peculiar, nearby, host galaxy where we have multi-wavelength data to study possible star-formation processes. I will also present how we can use in particular GRBs to study the ISM in high-redshift galaxies with absorption lines in the afterglow spectrum and present the first metallicity measurement of a short GRB host. Finally, I will review how and if we might be able to use these explosions to test the expansion of the Universe.