The 2017 detection of the in-spiral and merger of two neutron stars was a landmark discovery in astrophysics. Through a wealth of multi-messenger data, we now know that the merger of these ultracompact stellar remnants is a central engine of short gamma ray bursts and a site of r-process nucleosynthesis, where the heaviest elements in our universe are formed. The radioactive decay of unstable heavy elements produced in such mergers powers an optical and infra-red transient: The kilonova.
A key tool in understanding this observation — and the wealth of observations we expect going forward — is the forward modeling of the merger, its aftermath. This forward modeling requires many physics inputs, including general relativity, magnetohydrodynamics, weak interactions, nuclear reaction rates, and atomic opacities. In this talk, I discuss how this modeling is done, from end to end, with an emphasis on uncertainties and the role that laboratory astrophysics plays in our understanding and modeling of these observations. I also present recent progress in modeling one key aspect of the system, the accretion disk formed around the compact remnant.