Exoplanets & Exomoons

Doppler Tomography As A Tool For Characterising Exoplanet Atmospheres II: An Analysis of HD 179949 b

By Keith Cowing
Status Report
April 9, 2024
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Doppler Tomography As A Tool For Characterising Exoplanet Atmospheres II: An Analysis of HD 179949 b
An example of the detrending process as applied to data taken on July 16 2011. Top panel: the data after extraction using the CRIRES pipeline and the correction of bad pixels. Middle panel: the same data after aligning and normalising the spectra. Bottom panel: the final de-trended data after applying SYSREM, a high pass filter, and dividing each column by its standard deviation. Particularly noisy regions of the data have also been masked. It is the de-trended data presented in the bottom panel that is used in the subsequent Doppler tomography and cross-correlation analysis. — astro-ph.EP

High-resolution Doppler spectroscopy provides an avenue to study the atmosphere of both transiting and non-transiting planets. This powerful method has also yielded some of the most robust atmospheric detections to date.

Currently, high-resolution Doppler spectroscopy detects atmospheric signals by cross-correlating observed data with a model atmospheric spectrum. This technique has been successful in detecting various molecules such as H2O, CO, HCN and TiO, as well as several atomic species. Here we present an alternative method of performing high-resolution Doppler spectroscopy, using a technique known as Doppler tomography.

We present an analysis of HD 179949 b using Doppler tomography and provide Doppler tomograms confirming previous detections of CO at 2.3 microns, and H2O at both 2.3 microns, and 3.5 microns within the atmosphere of HD 179949 b, showing significantly lower background noise levels when compared to cross-correlation methods applied to the same data.

We also present a novel detection of H2O at 2.1 microns, as well as a tentative detection of CO on the night side of the planet at 2.3 microns. This represents the first observational evidence for molecular absorption in the night-side emission spectrum of an exoplanet using Doppler spectroscopy.

S. M. Matthews, C. A. Watson, E. J. W. de Mooij, T. R. Marsh, M. Brogi, S. R. Merritt, K. W. Smith, D. Steeghs

Comments: Accepted for publication in the Monthly Notices of the Royal Astronomical Society. 16 pages, 14 figures, 7 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2404.05652 [astro-ph.EP] (or arXiv:2404.05652v1 [astro-ph.EP] for this version)
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Submission history
From: Christopher Allan Watson
[v1] Mon, 8 Apr 2024 16:36:01 UTC (10,224 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) 🖖🏻