Atmospheres & Climate

Signatures Of X-ray Dominated Chemistry In The Spectra Of Exoplanetary Atmospheres

By Keith Cowing
Status Report
February 8, 2024
Filed under , , , , ,
Signatures Of X-ray Dominated Chemistry In The Spectra Of Exoplanetary Atmospheres
Wavelength-dependent contribution functions using low, R = 300, (left panel) and high, R = 50000, (right panel) resolution powers, displayed for the whole range of pressures (i.e., from p = 10βˆ’10 to 1 bar). The X-ray intensity is LX = 1030 erg s βˆ’1 . — astro-ph.EP

High-energy radiation from stars impacts planetary atmospheres deeply affecting their chemistry, providing departures from chemical equilibrium.

While the upper atmospheric layers are dominated by ionizations induced by extreme ultraviolet radiation, deeper into the atmosphere molecular abundances are controlled by a characteristic X-ray dominated chemistry, mainly driven by an energetic secondary electron cascade.

In this work, we aim at identifying molecular photochemically induced fingerprints in the transmission spectra of a giant planet atmosphere. We have developed a numerical code capable of synthesizing transmission spectra with arbitrary spectral resolution, exploiting updated infrared photoabsorption cross sections.

Chemical mixing ratios are computed using a photochemical model, tailored to investigate high energy ionization processes. We find that in case of high levels of stellar activity, synthetic spectra in both low and high resolutions show significant, potentially observable out-of-equilibrium signatures arising mainly from CO, CH4, C2H2, and HCN.

Daniele Locci, Giambattista Aresu, Antonino Petralia, Giuseppina Micela, Antonio Maggio, Cesare Cecchi-Pestellini

Comments: The paper has been accepted for publication in The Planetary Science Journal (PSJ)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2402.04688 [astro-ph.EP] (or arXiv:2402.04688v1 [astro-ph.EP] for this version)
Submission history
From: Daniele Locci
[v1] Wed, 7 Feb 2024 09:27:32 UTC (15,205 KB)

Astrobiology, Astrochemistry,

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) πŸ––πŸ»