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Paper: Optical Linear Polarization in the Case of Two Supernovae Associated to X-ray Flashes: XRF060218/SN2006aj and XRF080109/SN2008D
Volume: 449, Astronomical Polarimetry 2008: Science from Small to Large Telescopes
Page: 421
Authors: Gorosabel, J.; de Postigo, A. U.; Castro-Tirado, A. J.; Jel'inek, M.; Larionov; Guziy, S.; Augusteijn, T.; Fynbo, J.; Hjorth, J.; Malesani, D.; Xu, D.; Ferrero, P.; Kann, A.; Klose, S.; Rossi, A.; Llorente, A.; Madrid, J. P.
Abstract: We present the polarization monitoring carried out for two SNe associated with GRBs: XRF060218/SN2006aj and XRF080109/SN2008D. For XRF060218/SN2006aj we measured a mean polarization of P∼4% at 2.6-5.6 days after the X-ray event. This is the highest polarization value ever measured for a supernova. We derived the intrinsic polarization of XRF080109/SN2008D, assuming that the last polarization detection is due to the host galaxy. The resulting XRF060218/SN2006aj intrinsic polarization decayed as t–2, similarly as the one reported for SN2004dj. This decay can be explained by a circularization of the expansion geometry. Surprisingly the XRF060218/SN2006aj polarization position angle displayed a ≈ 100° rotation when we compare data taken before and after the light curve peak. On the other hand, XRF080109/SN2008D showed polarization values in the range 0.7–1.6%. A statistical analysis of the data distribution on the Stokes plane strongly suggests that XRF080109/SN2008D showed intrinsic variable polarization. Assuming that the Ib-type SN2007uy (another SN simultaneously imaged in the same host of XRF080109/SN2008D) is constant in the Stokes plane, then the Stokes parameters of XRF080109/ SN2008D evolve approximately on a straight line as expected for an axisymmetric expansion. These two examples illustrate how to obtain geometric information without resolving the emitting source.
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