Ni rp-process waiting point exist?*

The rp-process path depends heavily on the nuclear properties of proton-rich nuclei as well as the temperature-density trajectory of the X-ray burst. Often, branching points occur when proton captures and β decays have similar time-scales. The canonical rp-process path flows through the major waiting point at ⁵⁶Ni, but recent work has suggested that, depending on the conditions of the X-ray burst, a bypass can form beginning with the ⁵⁵Ni(p,γ) reaction. A strong bypass would allow material to move towards heavier nuclei faster, decreasing the A = 55-60 content of the resultant rp-process ashes, altering the thermal structure of the neutron star crust. Experimental work determining the important resonance states in ⁵⁶Cu as well as the measurement of the previously highly-uncertain ⁵⁶Cu mass have constrained the ⁵⁵Ni(p,γ)⁵⁶Cu rate significantly. Experimental results and rp-process network calculations will be presented to demonstrate the effect of the bypass. Future work aimed at reducing the remaining reaction rate uncertainties will also be presented.