H$lpha$ spectropolarimetry of RY?Tauri and PX Vulpeculae

摘要

Aims. To detect line effects using spectropolarimetry in order to find evidence of rotating disks and their respective symmetry axes in TTauri stars. Methods. We used the IAGPOL imaging polarimeter along with the Eucalyptus-IFU to obtain spectropolarimetric measurements of the TTauri stars RYTau (two epochs) and PXVul (one epoch). Evidence of line effects showing a loop in the Q-U diagram favors a compact rather than an extended source for the line photons in a rotating disk. In addition, the polarization position angle (PA) obtained using the line effect can constrain the symmetry axis of the disk. Results. RYTau shows a variable Hdouble peak in 2004-2005data. A polarization line effect is evident in the Q-U diagram for both epochs confirming a clockwise rotating disk. A single loop is evident in 2004 changing to a linear excursion plus a loop in 2005. Interestingly, the intrinsic PA calculated using the line effect is consistent between our two epochs (167). An alternative intrinsic PA computed from the interstellar polarization-corrected continuum and averaged between 2001-2005 yielded a PA137.This last value is closer to perpendicular to the observed disk direction (25), as expected from single scattering in an optically thin disk. For PXVul, we detected spectral variability in Halong with non-variable continuum polarization when compared with previous data. The Q-U diagram shows a well-defined loop in Hassociated with a counter-clockwise rotating disk. The symmetry axis inferred from the line effect has a PA91(with an ambiguity of 90). Our results confirm previous evidence that the emission line in TTauri stars has its origin in a compact source scattered off a rotating accretion disk. Key words: polarization - stars: individual: RYTau - stars: individual: PXVul - stars: circumstellar matter