We present low-resolution ( R \sim 90 ) and medium-resolution ( R \sim 2500 ) spectropolarimetry of Nova V475 Sct with the HBS instrument , mounted on the 0.91-m telescope at the Okayama Astrophysical Observatory , and with FOCAS , mounted on the 8.2-m Subaru telescope .
We estimated the interstellar polarization toward the nova from the steady continuum polarization components and H \alpha line emission components .
After subtracting the interstellar polarization component from the observations , we found that the H \alpha emission seen on 2003 October 7 was clearly polarized .
In the polarized flux spectrum , the H \alpha emission had a distinct red wing extending to \sim + 4900 km s ^ { -1 } and a shoulder around +3500 km s ^ { -1 } , showing a constant position angle of linear polarization \theta _ { * } \simeq 155 \arcdeg \pm 15 \arcdeg .
This suggests that the nova had an asymmetric outflow with a velocity of v _ { wind } \simeq 3500 km s ^ { -1 } or more , which is six times higher than the expansion velocity of the ionized shell at the same epoch .
Such a high-velocity component has not previously been reported for a nova in the ‘ moderately fast ’ speed class .
Our observations suggest the occurrence of violent mass-loss activity in the nova binary system even during the common-envelope phase .
The position angle of the polarization in the H \alpha wing is in good agreement with that of the continuum polarization found on 2003 September 26 ( p _ { * } \simeq 0.4 – 0.6 % ) , which disappeared within the following 2 d. The uniformity of the PA between the continuum polarization and the wing polarization on October 7 suggests that the axis of the circumstellar asymmetry remained nearly constant during the period of our observations .