Characterisation of the Planetary Nebula Tc 1 Based on VLT X-Shooter
  Observations
  We present a detailed analysis of deep VLT/X-Shooter observations of the
planetary nebula Tc 1. We calculate gas temperature, density, extinction, and
abundances for several species from the empirical analysis of the total line
fluxes. In addition, a spatially resolved analysis of the most intense lines
provides the distribution of such quantities across the nebula. The new data
reveal that several lines exhibit a double peak spectral profile consistent
with the blue- and red-shifted components of an expanding spherical shell. The
study of such components allowed us to construct for the first time a
three-dimensional morphological model, which reveals that Tc 1 is a slightly
elongated spheroid with an equatorial density enhancement seen almost pole on.
A few bright lines present extended wings (with velocities up to a few hundred
km/s), but the mechanism producing them is not clear. We constructed
photoionization models for the main shell of Tc 1. The models predict the
central star temperature and luminosity, as well as the nebular density and
abundances similar to previous studies. Our models indicate that Tc 1 is
located at a distance of approximately 2 kpc. We report the first detection of
the [Kr III] 6825 A emission line, from which we determine the Krypton
abundance. Our model indicates that the main shell of Tc 1 is matter bounded;
leaking H ionizing photons may explain the ionization of its faint AGB-remnant
halo.
