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ATMOSPHERIX: II- Characterising exoplanet atmospheres through transmission spectroscopy with SPIRou

By Keith Cowing
Status Report
August 31, 2023
Filed under , , , , , ,
ATMOSPHERIX: II- Characterising exoplanet atmospheres through transmission spectroscopy with SPIRou
Variations of photometric flux (top panel), airmass (panel 2), Geocentric-to-stellar rest frame RV correction (panel 3) and peak SNR per velocity bin during the two simulated transits of the HD 189733 b analog. On panels 1 and 4, the two different transits are respectively shown as blue dots and pink crosses. The vertical gray band indicates the primary transit of the simulated planet. The horizontal gray dashed line on the bottom panel indicates the average value of the peak S/N for the observed spectra — astro-ph.IM

In a companion paper, we introduced a publicly-available pipeline to characterise exoplanet atmospheres through high-resolution spectroscopy.

In this paper, we use this pipeline to study the biases and degeneracies that arise in atmospheric characterisation of exoplanets in near-infrared ground-based transmission spectroscopy. We inject synthetic planetary transits into sequences of SPIRou spectra of the well known M dwarf star Gl 15 A, and study the effects of different assumptions on the retrieval. We focus on (i) mass and radius uncertainties, (ii) non isothermal vertical profiles and (iii) identification and retrieval of multiple species. We show that the uncertainties on mass and radius should be accounted for in retrievals and that depth-dependent temperature information can be derived from high-resolution transmission spectroscopy data.

Finally, we discuss the impact of selecting wavelength orders in the retrieval and the issues that arise when trying to identify a single species in a multi-species atmospheric model. This analysis allows us to understand better the results obtained through transmission spectroscopy and their limitations in preparation to the analysis of actual SPIRou data.

F. Debras, B. Klein, J.-F. Donati, T. Hood, C. Moutou, A. Carmona, B. Charnay, B. Bézard, P. Fouqué, A. Masson, S. Vinatier, C. Baruteau, I. Boisse, X. Bonfils, A. Chiavassa, X. Delfosse, G. Hebrard, J. Leconte, E. Martioli, M. Ould-elkhim, V. Parmentier, P. Petit, W. Pluriel, F. Selsis, L. Teinturier, P. Tremblin, M. Turbet, O. Venot

Comments: Accepted in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2308.14511 [astro-ph.EP] (or arXiv:2308.14511v1 [astro-ph.EP] for this version)
Submission history
From: Florian Debras
[v1] Mon, 28 Aug 2023 11:57:38 UTC (12,065 KB)

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) 🖖🏻