  We present optical spectropolarimetric observations of Type Ic supernova (SN)
2007gr with Subaru telescope at 21 days after the maximum brightness (~37 days
after the explosion). Non-zero polarization as high as ~3% is observed at the
absorption feature of Ca II IR triplet. The polarization of the continuum light
is ~0.5% if we estimate the interstellar polarization (ISP) component assuming
that the continuum polarization has a single polarization angle. This suggests
that the axis ratio of the SN photosphere projected to the sky is different
from unity by ~10%. The polarization angle at the Ca II absorption is almost
aligned to that of the continuum light. These features may be understood by the
model where a bipolar explosion with an oblate photosphere is viewed from the
slightly off-axis direction and explosively synthesized Ca near the polar
region obscures the light originated around the minor axis of the SN
photosphere. Given the uncertainty of the ISP, however, the polarization data
could also be interpreted by the model with an almost spherically symmetric
photosphere and a clumpy Ca II distribution.
