Method and new tabulations for flux-weighted line-opacity and radiation
  line-force in supersonic media
  In accelerating and supersonic media, the interaction of photons with
spectral lines can be of ultimate importance. However, fully accounting for
such line forces currently can only be done by specialised codes in 1-D
steady-state flows. More general cases and higher dimensions require
alternative approaches. We presented a comprehensive and fast method for
computing the radiation line-force using tables of spectral line-strength
distribution parameters, which can be applied in arbitrary (multi-D,
time-dependent) simulations, including those accounting for the
line-deshadowing instability, to compute the appropriate opacities. We assumed
local thermodynamic equilibrium to compute a flux-weighted line opacity from
$>4$ million spectral lines. We derived the spectral line strength and
tabulated the corresponding line-distribution parameters for a range of input
densities $\rho\in[10^{-20},10^{-10}]gcm^{-3}$ and temperatures
$T\in[10^4,10^{4.7}]K$. We found that the variation of the line distribution
parameters plays an essential role in setting the wind dynamics in our models.
In our benchmark study, we also found a good overall agreement between the
O-star mass-loss rates of our models and those derived from steady-state
studies using more detailed radiative transfer. Our models reinforce that
self-consistent variation of the line-distribution parameters is important for
the dynamics of line-driven flows. Within a well-calibrated O-star regime, our
results support the proposed methodology. In practice, utilising the provided
tables, yielded a factor $>100$ speed-up in computational time compared to
specialised 1-D model-atmosphere codes of line-driven winds, which constitutes
an important step towards efficient multi-D simulations. We conclude that our
method and tables are ready to be exploited in various radiation-hydrodynamic
simulations where the line force is important.
