The Near-Infrared Polarization of the Pre-Planetary Nebula Frosty Leo
  We present a near-infrared imaging polarimetric study of the pre-planetary
nebula: Frosty Leo. The observations were carried out in J, H and K' bands
using the new polarimeter POLICAN mounted on the 2.1m telescope of the
Guillermo Haro Astrophysical Observatory, Sonora, Mexico. The most prominent
result observed in the polarization maps is a large and well defined dusty
envelope (35\arcsec\ diameter in H-band). The polarization position angles in
the envelope are particularly well ordered and nearly parallel to the equator
of the nebula (seen in J and H bands). The nebula presents a known bipolar
outflow and the envelope completely wraps around it. Within the bipolar lobes,
we find high polarization levels ranging from $60\%$ (J band) to $90\%$ (K'
band) and the polarization angles trace a centrosymmetric pattern. We found the
remnants of superwind shells at the edges of the bipolar lobes and the duration
of this phase is around 600 yrs. The origin of polarization features in the
nebula is most likely due to a combination of single and multiple scattering.
Our results clearly demonstrate new structures that provide new hints on the
evolution of Frosty Leo from its previous asymptotic giant branch phase.
