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 TOF-$Brho$ 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 $^{58,59}{rm Ti}$, $^{62}{rm V}$, $^{65}{rm Cr}$, $^{67,68}{rm Mn}$, and $^{69,70}{rm Fe}$. 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.