Astrochemistry

Detectability of Polycyclic Aromatic Hydrocarbons in the Atmosphere of WASP-6 b with JWST NIRSpec PRISM

By Keith Cowing

Status Report

astro-ph.EP

November 16, 2024

Filed under astro-ph.EP, astrochemistry, astronomy, atmosphere, Clouds, exoplanet, Haze, hot Saturn, Interstellar, interstellar medium, JWST, NIRSpec PRISM, petitRADTRANS, Polycyclic Aromatic Hydrocarbons, Spectroscopy, WASP-6 b

Detectability of Polycyclic Aromatic Hydrocarbons in the Atmosphere of WASP-6 b with JWST NIRSpec PRISM — Results for the offset retrieval runs. Top panel: Best-fitting spectra for the Cloudless and PAH models (HST STIS + ELT + TESS data in black, G141 and Spitzer data including the best-fitting offsets for both retrievals in blue and green, respectively). Bottom panel: Residuals are plotted for each model in the respective colors showing the deviation of the data points from the spectra in units of the corresponding transit depth error (𝜎). The shaded bars indicate the 1, 3 and 5 𝜎 regions. Finally, the subpanel presents the model quality, showcasing the evidences as absolute deviations (Δln𝑍) from the lower model (for details refer to Table A1) and the reduced 𝜒² — astro-ph.EP

Polycyclic Aromatic Hydrocarbons (PAHs) have been detected throughout the universe where they play essential roles in the evolution of their environments.

For example, they are believed to affect atmospheric loss rates of close-in planets and might contribute to the pre-biotic chemistry and emergence of life. Despite their importance, the study of PAHs in exoplanet atmospheres has been limited.

We aim to evaluate the possibility of detecting PAHs on exoplanets considering future observations using JWST’s NIRSpec PRISM mode. The hot Saturn WASP-6 b shows properties that are consistent with a potential PAH presence and is thus used as a case study for this work.

Here, we compare the likelihoods of various synthetic haze species and their combinations with the influence of PAHs on the transmission spectrum of WASP-6 b. This is possible by applying the atmospheric retrieval code petitRADTRANS to a collection of data from previous observations. Subsequently, by exploring synthetic, single transit JWST spectra of this planet that include PAHs, we assess if these molecules can be detected in the near future.

Previous observations support the presence of cloud/haze species in the spectrum of WASP-6 b. While this may include PAHs, the current data do not confirm their existence unambiguously.

Our research suggests that utilizing the JWST for future observations could lead to a notable advancement in the study of PAHs. Employing this telescope, we find that a PAH abundance of approximately 0.1 per cent of the ISM value could be robustly detectable.

Fabian Grübel, Karan Molaverdikhani, Barbara Ercolano, Christian Rab, Oliver Trapp, Dwaipayan Dubey, Rosa Arenales-Lope

Comments: 15 pages,11 figures, accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2411.07861 [astro-ph.EP] (or arXiv:2411.07861v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2411.07861
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Related DOI:
https://doi.org/10.1093/mnras/stae2532
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Submission history
From: Fabian Grübel
[v1] Tue, 12 Nov 2024 15:19:00 UTC (26,677 KB)
https://arxiv.org/abs/2411.07861
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) 🖖🏻

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