Measuring surface magnetic fields of red supergiant stars

摘要: RSG stars are very massive cool evolved stars. Recently, a weak magnetic field was measured at the surface of $\alpha$ Ori and this is so far only M-type supergiant for which direct detection has been reported. By extending search in sample late-type supergiants, we want to determine whether detected on common feature among supergiants. With spectropolarimeter Narval TBL undertook fields stars, analysed circular polarisation spectra using least-squares deconvolution technique. We detect Zeeman signatures stellar origin targets CE Tau, $\alpha^1$ Her $\mu$ Cep. For latter star, also show that cross-talk from strong linear signals star must be taken into account. Tau Cep, longitudinal component Gauss-level, such as $\alpha$~Ori. almost an order magnitude stronger Her. report variability Her, with changes good agreement typical atmospheric dynamics time-scales. non-detection yellow $\rho$ Cas. The two our sample, display similar Ori. post-RSG Cas suggests disappears, or least becomes undetectable present methods, later evolutionary stages. Our analysis supports proposed reclassification AGB star.