The 2200 A circumstellar dust absorption feature in the spectra of three bright RV Tauri stars.

Abstract

IUE observations of the 2200 A absorption feature of circumstellar dust were made of the three RV Tauri stars AC Her, U Mon, and R Sct. U Mon was found to have a dust shell with a much lower column density at 2200 A than R Sct and possibly AC Her, requiring U Mon to have a much more extended dust shell than R Sct to account for its greater infrared excess. AC Her and R Sct were observed twice, at different phases of their cycles, and no major change in the 2200 A absorption feature with phase was detected. Such a change would have supported the idea that the slight polarization of these stars' visual light is caused by the circumstellar dust.