Seminar in Hadronic Physics

Counting the protons in neutron star MXB 1659-29

Melissa Mendes

McGill University

In the past four years of my PhD research, I have investigated if a neutron star made only of neutrons, protons and leptons is consistent with neutron star's neutrino luminosities inferred from observations. This research question is interesting because there is no agreement in the theoretical community about whether the densities reached in the core of neutron stars would allow for the presence of exotic hadronic components such as hyperons, pion condensates, etc. or even non-hadronic components such as a quark phase. Therefore, there are many equations of state (EOS) available in the literature that could describe neutron stars, nonetheless, so far all neutron star structure observations, like NICER’s mass and radius measurements and inferred tidal deformabilities from gravitational wave measurements of neutron star mergers are consistent with the class of EOS studied in this research: the vanilla ones made only of neutrons, protons and leptons. Hence, our goal of this research has been to investigate what it takes for an EOS to reproduce cold neutron stars such as MXB 1659-29, in specific:

• whether neutrino luminosities of cold neutron stars are also compatible with these EOS and which one of the family of equations under study is favored, if any
• what kind of proton superconductivity and neutron superfluidity models are consistent with this neutrino luminosity.

With these results we can also speculate on the possibility that EOS with exotic components might explain this data and whether that scenario is favored.