News Summary Archives

Ground-Based Reconnaissance Observations Of 21 Exoplanet Atmospheres With The Exoplanet Transmission Spectroscopy Imager

By Keith Cowing

Status Report

astro-ph.EP

March 17, 2025

Filed under astro-ph.EP, atmosphere, ETSI, exoplanet, Hubble, imaging, Spectroscopy, Transmission spectroscopy

Ground-Based Reconnaissance Observations Of 21 Exoplanet Atmospheres With The Exoplanet Transmission Spectroscopy Imager — A visual comparison of transmission spectra measured for various planets during transit (red points) and out-oftransit (black points). The p-value of an Anderson-Darling test comparing the two measurements is shown it the title of each sub-figure. The out-of-transit measurements were generated via 1000 bootstrap simulations where the white-light transit signal (see Table 3) was injected at various times of mid-transit and measured the same way as the in-transit data. The top row of planets have a calculated p-value of p < 0.05 indicating the in-transit and out-of-transit data are statistically different from one another. The bottom row of planets have p-values of p > 0.05 indicating they are not statistically dis-similar to the boot-strap simulations. For these planets we additionally compared previous measurements from the Exoplanet Archive with a flat-line using an R 2 metric. We find the previous measurements all have an R 2 < 0.54 which suggests the atmospheric signal is likely consistent with a flat line and the consistency between in-transit and out-of-transit observations may be because the spectra is naturally featureless. -- astro-ph.EP

One of the most prolific methods of studying exoplanet atmospheres is transmission spectroscopy, which measures the difference between the depth of an exoplanet’s transit signal at various wavelengths and attempts to correlate the depth changes to potential features in the exoplanet’s atmosphere.

Here we present reconnaissance observations of 21 exoplanet atmospheres measured with the Exoplanet Transmission Spectroscopy Imager (ETSI), a recently deployed spectro-photometer on the McDonald Observatory Otto Struve 2.1 m telescope.

ETSI measurements are mostly free of systematics through the use of a novel observing technique called common-path multi-band imaging (CMI), which has been shown to achieve photometric color precision on-par with space-based observations (300ppm or 0.03%). This work also describes the various statistical tests performed on the data to evaluate the efficacy of the CMI method and the ETSI instrument in combination.

We find that none of the 8 comparisons of exoplanet atmospheres measured with ETSI and other observatories (including the Hubble Space Telescope) provide evidence that the spectra are statistically dissimilar. These results suggest that ETSI can provide initial transmission spectroscopy observations for a fraction of the observational and monetary overhead previously required to detect an exoplanet’s atmosphere.

Ultimately these reconnaissance observations increase the number of planets with transmission spectroscopy measurements by ~10% and provide an immediate prioritization of 21 exoplanets for future follow-up with more precious observatories, such as the James Webb Space Telescope. The reconnaissance spectra are available through the Filtergraph visualization portal at the URL: this https URL.

Ryan J. Oelkers, Luke M. Schmidt, Erika Cook, Mary Anne Limbach, D. L. DePoy, J. L. Marshall, Jimmy Ardoin, Mitchell Barry, Evan Batteas, Alexandra Boone, Brant Conway, Silvana Delgado Adrande, John D. Dixon, Enrique Gonzalez-Vega, Alexandra Guajardo, Landon Holcomb, Christian Lambert, Shravan Menon, Divya Mishra, Jacob Purcell, Zachary Reed, Nathan Sala, Noah Siebersma, Nhu Ngoc Ton, Raenessa M. L. Walker, Z. Franklin Wang, Kaitlin Webber

Comments: 28 pages, 8 figures, 11 tables, article published in AJ. ETSI data is available on request and spectra can be found at the URL this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2503.03930 [astro-ph.EP] (or arXiv:2503.03930v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2503.03930
Focus to learn more
Journal reference: AJ, 169, 134 (2025)
Related DOI:
https://doi.org/10.3847/1538-3881/ada557
Focus to learn more
Submission history
From: Ryan Oelkers
[v1] Wed, 5 Mar 2025 22:05:39 UTC (1,552 KB)
https://arxiv.org/abs/2503.03930
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