Spectropolarimetry of V854 centauri at minimum light: Clues to the geometry of the dust and emission-line region
Abstract
We have observed the RCB star V854 Cen during a very deep decline (Δm = 8.2) at the AAT. The continuum polarization is very high, ranging from 14% at 4200 A° to about 4% at 6500 A°. The polarization decreases across the emission lines but the polarized flux remains constant. This indicates that the emission lines are unpolarized, so the emission probably arises in a region unobscured by dust. In such a deep minimum, the visible continuum flux is probably almost entirely scattered light, which explains its high polarization. The scattered flux may arise in the same clouds contributing to the observed IR flux if the albedo is low and the grains forward throwing. The emission-line spectrum itself is very unusual for an RCB star in decline, with strong C2 bands and Balmer lines.