Irradiation-driven escape of primordial planetary atmospheres I. The ATES photoionization hydrodynamics code. (arXiv:2106.10294v2 [astro-ph.EP] UPDATED)

Irradiation-driven escape of primordial planetary atmospheres I. The ATES photoionization hydrodynamics code. (arXiv:2106.10294v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Caldiroli_A/0/1/0/all/0/1">Andrea Caldiroli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haardt_F/0/1/0/all/0/1">Francesco Haardt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gallo_E/0/1/0/all/0/1">Elena Gallo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Spinelli_R/0/1/0/all/0/1">Riccardo Spinelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malsky_I/0/1/0/all/0/1">Isaac Malsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rauscher_E/0/1/0/all/0/1">Emily Rauscher</a>

Intense X-ray and ultraviolet stellar irradiation can heat and inflate the
atmospheres of closely orbiting exoplanets, driving mass outflows that may be
significant enough to evaporate a sizable fraction of the planet atmosphere
over the system lifetime. The recent surge in the number of known exoplanets,
together with the imminent deployment of new ground and space-based facilities
for exoplanet discovery and characterization, requires a prompt and efficient
assessment of the most promising targets for intensive spectroscopic
follow-ups. To this purpose, we developed ATES (ATmospheric EScape); a new
hydrodynamics code that is specifically designed to compute the temperature,
density, velocity and ionization fraction profiles of highly irradiated
planetary atmospheres, along with the current, steady-state mass loss rate.
ATES solves the one-dimensional Euler, mass and energy conservation equations
in radial coordinates through a finite-volume scheme. The hydrodynamics module
is paired with a photoionization equilibrium solver that includes cooling via
bremsstrahlung, recombination and collisional excitation/ionization for the
case of a primordial atmosphere entirely composed of atomic hydrogen and
helium, whilst also accounting for advection of the different ion species.
Compared against the results of 14 moderately-to-highly irradiated planets
simulated with The PLUTO-CLOUDY Interface (TPCI), ATES yields remarkably good
agreement at a significantly smaller fraction of the computational time. A
convergence study shows that ATES recovers stable, steady-state hydrodynamic
solutions for systems with $log(-phi_p) lesssim 12.9 + 0.17log F_{rm
XUV}$. Incidentally, atmospheres of systems above this threshold are generally
thought to be undergoing Jeans escape. The code, which also features a
user-friendly graphic interface, is available publicly as an online repository.

Intense X-ray and ultraviolet stellar irradiation can heat and inflate the
atmospheres of closely orbiting exoplanets, driving mass outflows that may be
significant enough to evaporate a sizable fraction of the planet atmosphere
over the system lifetime. The recent surge in the number of known exoplanets,
together with the imminent deployment of new ground and space-based facilities
for exoplanet discovery and characterization, requires a prompt and efficient
assessment of the most promising targets for intensive spectroscopic
follow-ups. To this purpose, we developed ATES (ATmospheric EScape); a new
hydrodynamics code that is specifically designed to compute the temperature,
density, velocity and ionization fraction profiles of highly irradiated
planetary atmospheres, along with the current, steady-state mass loss rate.
ATES solves the one-dimensional Euler, mass and energy conservation equations
in radial coordinates through a finite-volume scheme. The hydrodynamics module
is paired with a photoionization equilibrium solver that includes cooling via
bremsstrahlung, recombination and collisional excitation/ionization for the
case of a primordial atmosphere entirely composed of atomic hydrogen and
helium, whilst also accounting for advection of the different ion species.
Compared against the results of 14 moderately-to-highly irradiated planets
simulated with The PLUTO-CLOUDY Interface (TPCI), ATES yields remarkably good
agreement at a significantly smaller fraction of the computational time. A
convergence study shows that ATES recovers stable, steady-state hydrodynamic
solutions for systems with $log(-phi_p) lesssim 12.9 + 0.17log F_{rm
XUV}$. Incidentally, atmospheres of systems above this threshold are generally
thought to be undergoing Jeans escape. The code, which also features a
user-friendly graphic interface, is available publicly as an online repository.

http://arxiv.org/icons/sfx.gif