Linear Spectropolarimetry of the 2011 Eruption of the Recurrent Nova T Pyx

ABRIDGED We investigate the temporal evolution of the intrinsic polarization of the 2011 eruption of the recurrent nova T Pyxidis and use its continuum and line-polarization signatures to constrain the geometry and kinematic structure of the ejecta. We analyzed nine epochs of VLT/FORS2 optical linear spectropolarimetry obtained between 24 and 70 days after discovery, from shortly before optical maximum to the early decline. The instrumental and interstellar polarization contributions were removed, with the latter estimated from the depolarization observed at the rest wavelengths of the Balmer emission components. We examined the continuum and the velocity-dependent intrinsic polarization across the Hbeta, Hgamma, and Hdelta P Cygni profiles. The intrinsic continuum polarization generally remains below 1% and is predominantly aligned at a position angle of approximately 95degrees, except near optical maximum, when an orthogonal component at approximately 185degrees temporarily dominates. The blueshifted Balmer absorptions display stronger polarization, frequently reaching 2%, associated with excursions and loops in the Q-U plane. At least two distinct velocity-dependent polarization components are detected: the higher-velocity absorption is preferentially associated with the 95degrees orientation, whereas the lower-velocity absorption generally traces the 185degrees orientation. The polarization peaks shift quasi-linearly towards higher blueshifted velocities with time in all three Balmer lines.