  The most recent data on beam asymmetries, $\Sigma$, and beam-target
asymmetries, $E$, from the CLAS Collaboration, together with the previous data
on differential cross sections and beam asymmetries from the CLAS and LEPS
Collaborations, for the $\gamma n \to K^+\Sigma^-$ reaction are studied based
on an effective Lagrangian approach in the tree-level Born approximation. The
$t$-channel $K$ and $K^\ast(892)$ exchanges, the $u$-channel $\Sigma$ exchange,
the interaction current, and the exchanges of $N$, $\Delta$, and their excited
states in the $s$ channel are considered in constructing the reaction
amplitudes to describe the available experimental data. The reaction mechanisms
of $\gamma n \to K^+\Sigma^-$ are analyzed, and the associated resonances'
parameters are extracted. The numerical results show that the $\Delta$ exchange
and the $N(1710)1/2^+$, $N(1880)1/2^+$, $N(1900)3/2^+$, and $\Delta(1920)3/2^+$
resonance exchanges in the $s$-channel dominate the $\gamma n \to K^+\Sigma^-$
reaction in the lower energy region, and the $t$-channel $K^\ast(892)$ exchange
plays a crucial role at forward angles in the higher energy region.
