Evolution of helium triplet transits of close-in gas giants orbiting K-dwarfs

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Autori principali: Allan, Andrew P., Vidotto, Aline A., D'Angelo, Carolina Villarreal, Santos, Leonardo A. Dos, Driessen, Florian A.
Natura: Preprint
Pubblicazione: 2023
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author Allan, Andrew P.
Vidotto, Aline A.
D'Angelo, Carolina Villarreal
Santos, Leonardo A. Dos
Driessen, Florian A.
author_facet Allan, Andrew P.
Vidotto, Aline A.
D'Angelo, Carolina Villarreal
Santos, Leonardo A. Dos
Driessen, Florian A.
contents Atmospheric escape in exoplanets has traditionally been observed using hydrogen Lyman-$α$ and H-$α$ transmission spectroscopy, but more recent detections have utilised the metastable helium triplet at 1083$~$nm. Since this feature is accessible from the ground, it offers new possibilities for studying atmospheric escape. Our goal is to understand how the observability of escaping helium evolves during the lifetime of a highly irradiated gas giant. We extend our previous work on 1-D self-consistent hydrodynamic escape from hydrogen-only atmospheres as a function of planetary evolution to the first evolution-focused study of escaping hydrogen-helium atmospheres. Additionally, using these novel models we perform helium triplet transmission spectroscopy. We adapt our previous hydrodynamic escape model to now account for both hydrogen and helium heating and cooling processes and simultaneously solve for the population of helium in the triplet state. To account for the planetary evolution, we utilise evolving predictions of planetary radii for a close-in 0.3$~M_{\rm Jup}$ gas giant and its received stellar flux in X-ray, hard and soft EUV, and mid-UV wavelength bins assuming a K dwarf stellar host. We find that the helium triplet signature diminishes with evolution. Our models suggest that young ($\lesssim 150$~Myr), close-in gas giants ($\sim 1$ to $2~R_{\rm Jup}$) should produce helium 1083$~$nm transit absorptions of $\sim 4\%$ or $\sim 7\%$, for a slow or fast-rotating K dwarf, respectively, assuming a 2$\%$ helium abundance.
format Preprint
id arxiv_https___arxiv_org_abs_2311_01313
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Evolution of helium triplet transits of close-in gas giants orbiting K-dwarfs
Allan, Andrew P.
Vidotto, Aline A.
D'Angelo, Carolina Villarreal
Santos, Leonardo A. Dos
Driessen, Florian A.
Earth and Planetary Astrophysics
Atmospheric escape in exoplanets has traditionally been observed using hydrogen Lyman-$α$ and H-$α$ transmission spectroscopy, but more recent detections have utilised the metastable helium triplet at 1083$~$nm. Since this feature is accessible from the ground, it offers new possibilities for studying atmospheric escape. Our goal is to understand how the observability of escaping helium evolves during the lifetime of a highly irradiated gas giant. We extend our previous work on 1-D self-consistent hydrodynamic escape from hydrogen-only atmospheres as a function of planetary evolution to the first evolution-focused study of escaping hydrogen-helium atmospheres. Additionally, using these novel models we perform helium triplet transmission spectroscopy. We adapt our previous hydrodynamic escape model to now account for both hydrogen and helium heating and cooling processes and simultaneously solve for the population of helium in the triplet state. To account for the planetary evolution, we utilise evolving predictions of planetary radii for a close-in 0.3$~M_{\rm Jup}$ gas giant and its received stellar flux in X-ray, hard and soft EUV, and mid-UV wavelength bins assuming a K dwarf stellar host. We find that the helium triplet signature diminishes with evolution. Our models suggest that young ($\lesssim 150$~Myr), close-in gas giants ($\sim 1$ to $2~R_{\rm Jup}$) should produce helium 1083$~$nm transit absorptions of $\sim 4\%$ or $\sim 7\%$, for a slow or fast-rotating K dwarf, respectively, assuming a 2$\%$ helium abundance.
title Evolution of helium triplet transits of close-in gas giants orbiting K-dwarfs
topic Earth and Planetary Astrophysics
url https://arxiv.org/abs/2311.01313