Nuclear Masses and Neutron Stars

TL;DR

This paper discusses how precise measurements of neutron-rich nuclei masses inform models of neutron star matter, focusing on crust composition and the impact of nuclear shell closures.

Contribution

It provides a detailed analysis of neutron-star crust composition using various nuclear models and recent mass measurements, highlighting the importance of shell closures.

Findings

N=50 and N=82 shell closures are crucial for crust composition.

Mass measurements constrain neutron-star crust models.

Sensitivity of crust composition to nuclear mass models is demonstrated.

Abstract

Precision mass spectrometry of neutron-rich nuclei is of great relevance for astrophysics. Masses of exotic nuclides impose constraints on models for the nuclear interaction and thus affect the description of the equation of state of nuclear matter, which can be extended to describe neutron-star matter. With knowledge of the masses of nuclides near shell closures, one can also derive the neutron-star crustal composition. The Penning-trap mass spectrometer ISOLTRAP at CERN-ISOLDE has recently achieved a breakthrough measuring the mass of 82Zn, which allowed constraining neutron-star crust composition to deeper layers (Wolf et al., PRL 110, 2013). We perform a more detailed study on the sequence of nuclei in the outer crust of neutron stars with input from different nuclear models to illustrate the sensitivity to masses and the robustness of neutron-star models. The dominant role of the N=50 and N=82 closed neutron shells for the crustal composition is confirmed.