  We report precision mass measurements of neutron-deficient gallium isotopes
approaching the proton drip line. The measurements of $^{60-63}$Ga performed
with the TITAN multiple-reflection time-of-flight mass spectrometer provide a
more than threefold improvement over the current literature mass uncertainty of
$^{61}$Ga and mark the first direct mass measurement of $^{60}$Ga. The improved
precision of the $^{61}$Ga mass has important implications for the
astrophysical rp process, as it constrains essential reaction Q-values near the
$^{60}$Zn waiting point. Based on calculations with a one-zone model, we
demonstrate the impact of the improved mass data on prediction uncertainties of
X-ray burst models. The first-time measurement of the $^{60}$Ga ground-state
mass establishes the proton-bound nature of this nuclide; thus, constraining
the location of the proton drip line along this isotopic chain. Including the
measured mass of $^{60}$Ga further enables us to extend the evaluated $T=1$
isobaric multiplet mass equation up to $A=60$.
