Asymmetries in the Type IIn SN2010jl
  Aims: We study possible signs of asymmetry in the luminous Type IIn SN2010jl,
to obtain independent information on the explosion geometry. Methods: We
obtained optical linear spectropolarimetry of SN2010jl two weeks after the
discovery, in the spectral range 3700-8800 A. Results: The object exhibits a
continuum polarization at a very significant and almost constant level
(1.7-2.0%). Marked line depolarization is seen at the positions of the
strongest emission features, like Halpha and Hbeta. This implies that the line
forming region is well above the photosphere. The continuum polarization level
(1.7-2.0%) indicates a substantial asphericity, of axial ratio <=0.7. The
almost complete depolarization seen at Halpha suggests a very low level of
interstellar polarization (<=0.3%). This rules out the presence of relevant
amounts of dust in the progenitor environment at the time of our observations.
From a polarimetric point of view, SN2010jl appears to be very similar to the
two other well studied Type IIn SNe 1997eg and 1998S, establishing a strong
link within this class of objects.
