Beta equilibrium in neutron star merger conditions

Steven Harris, Department of Physics, Washington University
April 6, 2018 at 12:00 pm
241 Compton
Event Description 

Neutron stars are made up of cold, neutrino-transparent nuclear matter that is charge neutral and in beta equilibrium. The traditional statement of beta equilibrium is that the proton and electron chemical potentials add up to the neutron chemical potential. Since neutron star mergers can reach temperatures of tens of MeV, it is important to understand the beta equilibrium condition at these high temperatures. By calculating the rates of the Urca processes, we find that for temperatures above about 1 MeV, the beta equilibrium condition must be modified by including an isospin chemical potential which increases with the temperature, up to a maximum value of about 30 MeV. This modification of the beta equilibrium condition could have consequences for bulk viscosity in neutron star mergers.