Exoplanetology: Exoplanets & Exomoons

sunset: A Database Of Synthetic Atmospheric-escape Transmission Spectra For Nearly Every Transiting Planet

By Keith Cowing

Status Report

astro-ph.EP

October 7, 2024

Filed under astro-ph.EP, exoplanet, Spectroscopy, transiting planet

sunset: A Database Of Synthetic Atmospheric-escape Transmission Spectra For Nearly Every Transiting Planet — Top: Stellar spectral energy distribution (SED) templates used in this work. The A0 and A7 spectra are based on the work of Fossati et al. (2018), the solar spectrum is from the TIMED and SORCE missions (Woods et al. 2005; Rottman 2005), and the rest of the spectra are from the MUSCLES survey (France et al. 2016; Youngblood et al. 2016; Loyd et al. 2016; Wilson et al. 2021; Behr et al. 2023). Bottom: The integrated XUV flux (λ < 911 Å) of each SED, as a function of the effective temperature of the star (scatter points; see also Table 1). Small black points indicate SEDs in the MUSCLES database that we do not use. The grey histogram (read from the right y-axis) shows the host star effective temperatures of the initial planet population. Planets are assigned the SED template of the closest stellar spectral type. If the spectral type is not reported, the SED template of the star with the closest effective temperature is assigned. -- astro-ph.EP

Studying atmospheric escape from exoplanets can provide important clues about the formation and evolution of exoplanets. Observational evidence of atmospheric escape has been obtained through transit spectroscopy in strong spectral lines of various atomic species.

In recent years, the number of exoplanets that have been targeted in this way has grown rapidly, mainly by observations of the metastable helium triplet.

Even with this larger sample of exoplanets, many aspects of atmospheric escape remain not fully understood, such as the role of the stellar high-energy spectrum and planetary magnetic field, highlighting the need for additional observations.

This work aims to identify the best targets for observations in various spectral lines. Using the atmospheric escape code sunbather, we calculate a synthetic transmission spectrum of nearly every transiting exoplanet currently known. This database of spectra, named sunset, is publicly available.

We introduce metrics based on the spectral line strengths and system distance or magnitude, which allow swift identification of the most favorable targets. By analyzing the complete set of spectra from a demographic perspective, we find that the strengths of many spectral lines do not correlate strongly with the atmospheric mass-loss rate, suggesting that a nondetection does not immediately rule out an escaping atmosphere.

Our model spectra show only a weak correlation between the XUV (X-ray and extreme UV) flux and the helium line strength, affirming that the absence of such a trend found by observational works is in fact as expected.

A direct comparison between our synthetic spectra and the sample of observed metastable helium spectra shows that they are generally consistent within the large model uncertainties. This suggests that by and large, photoevaporation is able to explain the current metastable helium census.

Dion Linssen, Antonija Oklopčić, Morgan MacLeod

Comments: Submitted to A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2410.03228 [astro-ph.EP] (or arXiv:2410.03228v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2410.03228
Focus to learn more
Submission history
From: Dion Linssen
[v1] Fri, 4 Oct 2024 08:30:31 UTC (14,825 KB)
https://arxiv.org/abs/2410.03228

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

Follow on Twitter