New insight on Young Stellar Objects accretion shocks – a claim for NLTE opacities -. (arXiv:1904.09156v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Sa_L/0/1/0/all/0/1">Lionel de Sá</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chieze_J/0/1/0/all/0/1">Jean-Pierre Chièze</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stehle_C/0/1/0/all/0/1">Chantal Stehlé</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hubeny_I/0/1/0/all/0/1">Ivan Hubeny</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lanz_T/0/1/0/all/0/1">Thierry Lanz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cayatte_V/0/1/0/all/0/1">Véronique Cayatte</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Delahaye_F/0/1/0/all/0/1">Franck Delahaye</a>
Context. Accreted material onto CTTSs is expected to form a hot
quasi-periodic plasma structure that radiates in X-rays. Simulations of this
phenomenon only partly match with observations. They all rely on the assumption
that radiation and matter are decoupled, and use in addition a static model for
the chromosphere. Aims. We test the validity of these two assumptions in
refining the physics included in existing 1D models, and we propose guides for
further improvement. Methods. We simulate accretion columns falling onto a
stellar chromosphere using the 1D ALE code AstroLabE. This code solves the
hydrodynamics equations along with the two first momenta equations for
radiation transfer, with the help of a dedicated opacity table for the coupling
between matter and radiation. We derive the total electron and ions densities
from collisional-radiative NLTE ionization equilibrium. Results. The
chromospheric acoustic heating has an impact on the duration of the cycle and
on the structure of the heated slab. In addition, the coupling between
radiation and hydrodynamics leads to a dynamical heating of the accretion flow
and the chromosphere, leading to a possible unburrial of the whole column.
These two last conclusions are in agreement with the computed monochromatic
flux. Both effects (acoustic heating and radiation coupling) have an influence
on the amplitude and temporal variations of the net X ray luminosity.
Context. Accreted material onto CTTSs is expected to form a hot
quasi-periodic plasma structure that radiates in X-rays. Simulations of this
phenomenon only partly match with observations. They all rely on the assumption
that radiation and matter are decoupled, and use in addition a static model for
the chromosphere. Aims. We test the validity of these two assumptions in
refining the physics included in existing 1D models, and we propose guides for
further improvement. Methods. We simulate accretion columns falling onto a
stellar chromosphere using the 1D ALE code AstroLabE. This code solves the
hydrodynamics equations along with the two first momenta equations for
radiation transfer, with the help of a dedicated opacity table for the coupling
between matter and radiation. We derive the total electron and ions densities
from collisional-radiative NLTE ionization equilibrium. Results. The
chromospheric acoustic heating has an impact on the duration of the cycle and
on the structure of the heated slab. In addition, the coupling between
radiation and hydrodynamics leads to a dynamical heating of the accretion flow
and the chromosphere, leading to a possible unburrial of the whole column.
These two last conclusions are in agreement with the computed monochromatic
flux. Both effects (acoustic heating and radiation coupling) have an influence
on the amplitude and temporal variations of the net X ray luminosity.
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