  Differential cross sections and photon beam asymmetries have been measured
for the gamma n -> K+ Sigma- and gamma p -> K+ Sigma0 reactions separately
using liquid deuterium and hydrogen targets with incident linearly polarized
photon beams of Egamma=1.5-2.4 GeV at 0.6<cosTheta<1. The cross section ratio
of sigma(K+Sigma-)/sigma(K+Sigma0), expected to be 2 on the basis of the
isospin 1/2 exchange, is found to be close to 1. For the K+Sigma- reaction,
large positive asymmetries are observed indicating the dominance of the
K*-exchange. A large difference between the asymmetries for the K+Sigma- and
K+Sigma0 reactions can not be explained by simple theoretical considerations.
