Polarimetry of Supernova SN 1987A - A Dust Shell Model

Abstract

Polarimetric measurements of SN1987A in BVR bands were made on March 6 and 7. These observations along with the polarimetric data reported by various other authors within first 30 days of explosion have been discussed. There are atleast two intrinsic sources which contribute to the observed polarization; one source being the dust shell around SN1987A as is indicated by the wavelength dependence of linear and circular polarization and other being due to the non-thermal synchrotron radiation from the exploding star itself. A dust shell model to explain polarization observations has been suggested. From the time variation of the wavelength dependence of linear polarization, the optical depth is found to be about 0.6, the radius of the dust shell about 0.04 pc and the grain size to be smaller than the interstellar grain size. The temperature of the dust shell is expected to be around 200 K. Based on this dust shell model, infrared excess beyond 10 micron has been found to be in agreement with the observed values.