Measurement of the Gamow-Teller strength distributions via the (t,$^{3}$He$\gamma$) reactions on $^{45}$Sc and $^{46}$Ti

Electron captures (EC) of \textit{pf}-shell nuclei play an important role in pre-supernova stellar evolution and crustal heating of neutron stars. Astrophysical models show clear sensitivity to the details of the Gamow-Teller (GT) strength distributions, which have been extensively studied by means of charge-exchange reactions. In the present work, we measured the GT strength distributions in some of the lightest \textit{pf}-shell nuclei, ${}^{45}\mathrm{Ca}$ and ${}^{46}\mathrm{Sc}$, via the $(t,{}^{3}\mathrm{He}\gamma)$ reaction on stable ${}^{45}\mathrm{Sc}$ and ${}^{46}\mathrm{Ti}$ stationary targets at $E _t = 115 \, \mathrm{MeV}/\mathrm{nucleon}$ using the GRETINA array and the S800 spectrometer at the NSCL. Coincidence measurement with deexcitation $\gamma$ rays from the residual nuclei allowed us to study the detailed structure of low-lying GT strength, which is of particular importance for astrophysical applications. In this presentation, we will report preliminary results of the experiment and compare them to theoretical calculations.