Polarimetry of evolved stars - III. RV Tau and R CrB stars

摘要: We present broadband optical polarimetry, and infrared photometry, of eight RV Tau-type five R CrB-type stars; much the photometry polarimetry was obtained simultaneously. For nine objects polarimetric data is reported for first time. have estimated subtracted interstellar component polarization, allowing us to determine level intrinsic polarization. In some cases this is $\simeq$1%–2% even when star in a bright photometric state. consider be evidence presence permanent clumpy non-spherical dust shells around RV Tau R CrB-type stars we observed. Our lead conclude that, most our programme stars, neutral extinction must significant their circumstellar envelopes. Apart from brightness variations due pulsations changes effective temperature there clear wavelength-independent flux – with amplitude from $0\fm 5$ to $1\fm 0$ implying large ($a\ga 0.15$$\,\mu$m) particles. Rapid (~2 hours) evolution distribution at of ~$0\fm 6$ JHKL bands detected the RV Tau R Sct.