Nuclear mass measurements map the structure of atomic nuclei and accreting neutron stars

We present mass excesses (ME) of neutron-rich isotopes of Ar through Fe, obtained via time of flight Bρ mass spectrometry at the National Superconducting Cyclotron Laboratory. Our new results have significantly reduced systematic uncertainties relative to a prior analysis, enabling the first determination of ME for Ti58,59,V62,Cr65,Mn67,68, and Fe69,70. Our results show the N=34 subshell weaken at Sc and vanish at Ti, along with the absence of an N=40 subshell at Mn. This leads to a cooler accreted neutron star crust, highlighting the connection between the structure of nuclei and neutron stars.