Spectropolarimetry of SN2011fe (PTF11kly) in M101 at Early Times
ATel #3612; Paul Smith, Nathan Smith, Peter Milne, and Grant Williams (Steward Observatory, U. Arizona) and Buell Jannuzi (NOAO)
on 31 Aug 2011; 00:41 UT
Credential Certification: Nathan Smith (nathans@as.arizona.edu)
Subjects: Optical, Supernovae, Transient
We have obtained spectropolarimetry of the young Type Ia supernova
SN2011fe (PTF11kly) using the SPOL spectropolarimeter mounted on the
Bok 90-inch telescope at Kitt Peak. The data were obtained on the
night of August 29 UT, covering the wavelength range 4000--7550 A with
roughly 20 A resolution. The measured degree of polarization is
wavelength-dependent. The red continuum has a polarization of
approximately 0.2%, while higher degrees of polarization of 0.2%-0.3%
occur in parts of the spectrum also exhibiting broad absorption
troughs, including Si II 6355. The observed wavelength dependence of
polarization and its position angle - particularly regions of the
spectrum associated with broad spectral features - ensure
that the observed polarized radiation is intrinsic to SN2011fe and
not interstellar polarization within M101 or an instrumental
residual. The polarization position angle changes significantly; at
blue wavelengths between 4675 and 4875 A the position angle is about
145 degrees, but beyond 6000 A the position angle is approximately 55
degrees. Two unpolarized standards were observed to allow removal of
any instrumental signatures on the measured spectrum of the polarized
radiation, and two field stars were observed to correct for
interstellar polarization.
