Seminario A. Neuweiler

Il giorno 22 novembre alle ore 14 preso l'aula 412, Anna Neuweiler (University of Potsdam) terra' un seminario dal titolo

Simulating Binary Neutron Star Mergers and their Kilonova Light Curves

Abstract
The various phenomena of binary neutron star mergers allow us to study and explore a plethora of topics in modern physics, covering research areas from cosmic to subatomic scales. In addition to gravitational waves, electromagnetic signals may be generated in the ejected material, such as the kilonova, which is triggered by the radioactive decay of the elements formed in the ejecta. Simulations based on numerical relativity are crucial to understand the nature of these phenomena and to create accurate models against which observational data can be compared.
We can use the ejecta data from these simulations as input to radiative transfer simulations to obtain the kilonova directly related to the binary parameters. However, numerical-relativity simulations are usually very short and cover only a few tens of milliseconds after the merger due to the high computational costs. Typically, radiative transfer codes subsequently assume a homologous expansion of the outflowing material, which is not necessarily valid at this stage. In fact, we found in our simulations that the actual expansion deviates by more than 30 % from a homologous one until about 100ms after the merger. To determine the impact on the kilonova light curves, we used ejecta data extracted at different times, which showed negligible deviations only for extraction times later than ~ 80ms after the merger. These results highlight the need for a more careful approach in linking numerical-relativity simulations with radiative transfer calculations and motivate ongoing efforts to optimize this process for accurate light curve modeling.