  Background: The nucleosynthesis of several proton-rich nuclei is determined
by radiative proton-capture reactions on unstable nuclei in nova explosions.
One such reaction is $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$, which links the
NeNa and MgAl cycles in oxygen-neon (ONe) novae.
  Purpose: To extract $^{23}{\rm Mg}(p,\gamma)$ resonance strengths from a
study of proton-unbound states in $^{24}{\rm Al}$, produced via the
$^{24}$Mg($^{3}$He,$t$) reaction.
  Methods: A beam of $^3 {\rm He}^{2+}$ ions at 50.7 MeV was used to produce
the states of interest in $^{24}$Al. Proton-triton angular correlations were
measured with a $K=600$ QDD magnetic spectrometer and a silicon detector array,
located at iThemba LABS, South Africa.
  Results: We measured the excitation energies of the four lowest
proton-unbound states in $^{24}$Al and place lower-limits on $\Gamma_p/\Gamma$
values for these four states. Together with shell-model calculations of partial
gamma widths, the experimental data are also used to determine resonance
strengths for the three lowest $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$
resonances.
  Conclusions: The energy of the dominant first $^{23}{\rm Mg}(p,\gamma)$
resonance is determined to be $E_{r} = 478 \pm 4$ keV, with a resonance
strength $\omega \gamma = 19 \pm 9$ meV.
