Issue |
A&A
Volume 688, August 2024
|
|
---|---|---|
Article Number | A43 | |
Number of page(s) | 17 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/202450240 | |
Published online | 02 August 2024 |
The open-source sunbather code: Modeling escaping planetary atmospheres and their transit spectra
1
Anton Pannekoek Institute for Astronomy, University of Amsterdam,
Science Park 904,
1098
XH
Amsterdam,
The Netherlands
e-mail: d.c.linssen@uva.nl
2
Center for Astrophysics | Harvard & Smithsonian,
60 Garden Street, MS-16,
Cambridge,
MA
02138,
USA
Received:
4
April
2024
Accepted:
7
June
2024
Atmospheric escape is thought to significantly influence the evolution of exoplanets, especially sub-Jupiter planets on short orbital periods. Theoretical models predict that hydrodynamic escape could erode the atmospheres of such gaseous planets, leaving only a rocky core. Deriving atmospheric mass-loss rates from observations is necessary to check these predictions. One of the ways to obtain mass-loss-rate estimates is to fit transit spectra of the 10 830 Å helium or UV metal lines with Parker wind models. We aim to provide the community with a tool that enables this type of analysis, and present sunbather, an open-source Python code that can be used to model escaping exoplanet atmospheres and their transit spectra. sunbather incorporates the Parker wind code p-winds and the photoionization code Cloudy, with the ability to calculate any currently known spectral tracer, using an arbitrary atmospheric composition. With sunbather, we investigate how the atmospheric structure of a generic hot-Neptune planet depends on metallicity. We find that the mass-loss rate drops by roughly one order of magnitude as we increase the metallicity from solar to 50 times solar. Line cooling by metal species is already important for a solar composition, and is even more so at higher metallicity. We then demonstrate how sunbather can be used to interpret observations of spectral lines that form in the upper atmosphere. We fit the observed helium spectrum of the mini-Neptune TOI-2134 b and show how, even for helium data, the inferred mass-loss rate can change by a factor of up to three, depending on the assumed metallicity.
Key words: methods: numerical / planets and satellites: atmospheres / planets and satellites: gaseous planets
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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