T Tauri stars : Optical lucky imaging polarimetry of HL and XZ Tau

Abstract: Optical lucky imaging polarimetry of HL Tau and XZ Tau in the Taurus-Auriga molecular cloud was carried out with the instrument PolCor at the Nordic Optical Telescope (NOT). The results show that in both the V- and R-band HL Tau show centrosymmetric structures of the polarization angle in its northeastern outflow lobe (degree of polarization ~30%). A C-shaped structure is detected which is also present at near-IR wavelengths (Murakawa, 2008), and higher resolution optical images (Stapelfeldt, 1995). The position angle of the outflow is 47.5+-7.5 degrees, which coincides with previous measurements and the core polarization is observed to decrease with wavelength and a few scenarios are reviewed. Measuring the outflow witdh versus distance and wavelength shows that the longer wavelengths scatter deeper within the cavity wall of the outflow. In XZ Tau the binary is partially resolved, it is indicated by an elongated intensity distribution. The polarization of the parental cloud is detected in XZ Tau through the dichroic extinction of starlight. Lucky imaging at the NOT is a great way of increasing the resolution, shifting increases the sharpness by 0.1 asec and selection the sharpest frames can increase the seeing with 0.4 asec, perhaps more during better conditions.