Nuclear Physics of the Outer Crust of Accreting Neutron Stars

The thermal structure of the outer layers of neutron stars that have accreted material from a binary companion impacts a number of astronomical observables, such as the x-ray burst and superburst ignition frequencies and the cooling of transiently accreting neutron stars after accretion turn-off. The thermal and compositional structure of accreted neutron star crusts is determined by the host of nuclear processes occurring on and near the neutron star surface. The thermal structure of the outer crust is primarily determined by the strength of heating and cooling resulting from electron-capture reactions. This talk will discuss the recently discovered shallow Urca cooling process occurring in the neutron star outer crust, with an emphasis on the impact recent nuclear physics results have on the strength of the cooling inferred for the A$=$56 electron-capture chain. The impact of these results on astronomical observations, as well as future directions for shallow Urca cooling research will briefly be discussed.