Evidence for Dynamically Driven Formation of the GW170817 Neutron Star Binary in NGC 4993

Understand

We present a study of NGC 4993, the host galaxy of the GW170817 gravitational wave event, the GRB170817A short gamma-ray burst (sGRB) and the AT2017gfo kilonova.

• We use Dark Energy Camera imaging, AAT spectra and publicly available data, relating our findings to binary neutron star (BNS) formation scenarios and merger delay timescales.
• NGC4993 is a nearby (40 Mpc) early-type galaxy, with $i$-band S\'ersic index $n=4.0$ and low asymmetry ($A=0.04\pm 0.01$).
• These properties are unusual for sGRB hosts.