THE VISUAL AND ULTRAVIOLET POLARIMETRIC DATA OF α CAMELOPARDALIS AND κ CASSIOPEIA: EVIDENCE OF SHOCKED REGIONS

摘要

The OB supergiants α Cam and κ Cas are intrinsically very similar stars at comparable distances. Apart from a constant offset in the polarization of approx = 0.2%, both stars exhibit the same polarimetric variation between 1400 and 8000 A. Several possible mechanisms to explain the polarimetric observations are investigated. We propose that the polarization mechanism may be due to grain formation in an extended shell where the stellar wind and the interstellar medium interact. If this interpretation is correct, then it implies that the physical process giving rise to grain formation is not strongly correlated to the stellar wind parameters.