Polarimetric observations of the RV Tauri star AR Puppis

Abstract

UBVRI polarimetry of AR Pup is presented. Large variations are seen both in the amount and direction of polarization. On one occasion, the polarization in U was found to be as high as 14.6 percent. Polarization level increases rapidly near about the times of primary minima and decreases comparatively slowly afterwards. The P(lambda) curve is found to exhibit a wide range of shapes. The Stokes parameters Q and U in UBVR filter bands observed during JD 2446471-508 are found to lie on separate straight lines. Circumstantial evidences suggest that the origin of a major portion of polarization observed in AR Pup is due to grain scattering in more localized transient regions probably close to the photosphere and not in the infrared emitting extended circumstellar dust envelope. The regular changes seen in the P(lambda) curve during JD 2446471-508 indicate that changes in the grain size distribution are systematic.