We present single-epoch spectropolarimetry of the Type II supernovae ( SNe II ) 1997ds , 1998A , and 1999gi .
SN 1997ds and SN 1998A were both observed during the early photospheric phase , less than 50 days after explosion , while spectropolarimetry of SN 1999gi was obtained near the start of the transition to the nebular phase , about 110 days after explosion .
Uncorrected for interstellar polarization ( ISP ) , SN 1997ds is characterized by p _ { V } = 0.85 \pm 0.02 \% , SN 1998A has p _ { V } = 0.24 \pm 0.05 \% , and SN 1999gi is polarized at p _ { V } = 5.72 \pm 0.01 \% .
SN 1997ds and SN 1999gi exhibit distinct polarization modulations ( up to \Delta p _ { tot } = 1.6 \% in SN 1997ds and \Delta p _ { tot } = 1.0 \% in SN 1999gi ) at the wavelengths of the strongest spectral line features .
While no spectral polarization features could be observed in SN 1998A , the data are insensitive to polarization features at the levels confirmed in the other two objects .

The low continuum polarization inferred for SN 1997ds and SN 1998A and the amplitude of ( or limits on ) the polarization modulations are consistent with those measured at similar epochs for SN 1987A and the Type II-plateau SN 1999em , and supports the growing consensus that core-collapse events with hydrogen envelopes substantially intact at the time of explosion are not significantly aspherical during the early photospheric phase .
The spectral shape of the high continuum polarization of SN 1999gi closely resembles a “ Serkowski ” ISP curve ( characterized by p _ { max } = 5.8 \%, \theta = 154 ^ { \circ } , { and } \lambda _ { max } = 5300 Å ) , and is inconsistent with the wavelength-independent nature of electron scattering expected for an aspherical SN atmosphere .
Since Galactic reddening is minimal along this line-of-sight , the majority of the observed polarization in SN 1999gi is believed to be due to ISP of the host galaxy , although significant ( up to p \approx 2 \% ) intrinsic polarization can not be ruled out .
The potential power of SN spectropolarimetry to study the properties of interstellar dust in external galaxies is described and applied to the SN 1999gi data , where it is shown that if the polarization is indeed predominantly interstellar in origin , then R _ { V } = 3.0 \pm 0.2 for the dust along this line-of-sight in NGC 3184 .