  The Gamow-Teller strength for the transition from the ground state of 13C to
the T=1/2, J^pi=3/2- excited state at 3.51 MeV in 13N is extracted via the
13C(3He,t) reaction at 420 MeV. In contrast to results from earlier (p,n)
studies on 13C, a good agreement with shell-model calculations and the
empirical unit cross section systematics from other nuclei is found. The
results are used to study the analog 13N(e-,v_e)13C reaction, which plays a
role in the pre-explosion convective phase of type Ia supernovae. Although the
differences between the results from the (3He,t) and (p,n) data significantly
affect the deduced electron-capture rate and the net heat-deposition in the
star due to this transition, the overall effect on the pre-explosive evolution
is small.
