Nuclear masses and neutron stars

• We use the new Penning-trap mass measurement of 82Zn to study its implications for the outer crust of neutron stars.
• By testing 25 different nuclear mass models, recent results excluding 82Zn from the crust could be confirmed.
• We further validate that up to a density of 5 × 1010 g/cm3, the crustal composition is determined by experimental data.
• The conclusion that magic shells (N = 50, 82) are a key nuclear-structure effect for the crustal composition was strengthened.
• The link of the mass of 54Ca to advances in the ab initio description of neutron matter has been shown.

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 [1]. 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.

Figure optionsDownload high-quality image (164 K)Download as PowerPoint slide