Exoplanets & Exomoons

JWST COMPASS: NIRSpec/G395H Transmission Observations of the Super-Earth TOI-836b

By Keith Cowing
Status Report
April 2, 2024
Filed under , , , , , , , ,
JWST COMPASS: NIRSpec/G395H Transmission Observations of the Super-Earth TOI-836b
Top, Upper Panels: Individual visit transmission spectra for ExoTiC-JEDI (left, purples) and Eureka! (right, greens). Lower Panel: Difference between individual visit transmission spectra for ExoTiC-JEDI (left) and Eureka! (right). On average, the ExoTiC-JEDI reductions for visit 1 and visit 2 are consistent to within 39 ppm, while the Eureka! reductions agree to within 48 ppm. The ExoTiC-JEDI and Eureka! reductions are consistent with each other to within the median transit depth uncertainty for both visit 1 and visit 2. Bottom, Upper Panel: Weighted average transmission spectrum from the two visits from the ExoTiC-JEDI (purple) and Eureka! (light green) reductions and joint fit transmission spectrum from the Eureka! reduction (dark green). Lower Panel: Difference between each of the combined ExoTiC-JEDI and Eureka! transmission spectra in ppm. As the difference between the two Eureka! methods is less the 5 ppm (black line), the two ExoTiC-JEDI– Eureka! lines are difficult to distinguish (coloured lines). On average, the combined visit Eureka! and ExoTiC-JEDI spectra are consistent to within 10 ppm. — astro-ph.EP

We present two transit observations of the ~870K, 1.7RE super-Earth TOI-836b with JWST NIRSpec/G395H, resulting in a 2.8-5.2μm transmission spectrum. Using two different reduction pipelines, we obtain a median transit depth precision of 34ppm for Visit 1 and 36ppm for Visit 2, leading to a combined precision of 25ppm in spectroscopic channels 30 pixels wide (~0.02μm).

We find that the transmission spectrum from both visits is well fit by a zero-sloped line by fitting zero-sloped and sloped lines, as well as step functions to our data. Combining both visits, we are able to rule out atmospheres with metallicities <250xSolar for an opaque pressure level of 0.1 bar, corresponding to mean molecular weights to <6gmol−1. We therefore conclude that TOI-836b does not have an H2-dominated atmosphere, in possible contrast with its larger, exterior sibling planet, TOI-836c.

We recommend that future proposals to observe small planets exercise caution when requiring specific numbers of transits to rule out physical scenarios, particularly for high metallicities and planets around bright host stars, as PandExo predictions appear to be more optimistic than that suggested by the gains from additional transits implied by our data.

Mass-radius plots for the population of small exoplanets demonstrating possible interior compositions as calculated by SMINT, where the colour of each marker represents either the bulk H2-He (top) or bulk water (bottom) mass fractions. The planets in the TOI-836 system are denoted by star-shaped markers. Density curves for the Earth-like and 50 wt% liquid water compositions (Zeng & Jacobsen 2016); 50% and 100% steam atmospheres assuming Teq = 600 K and an Earth-like core (Aguichine et al. 2021); and 0.1%, 1%, 2% and 5% H2-He composition assuming an age of 5 Gyr (Lopez & Fortney 2014) are also plotted for reference. The background planet population is obtained from the NASA Exoplanet Archive. — astro-ph.EP

Lili Alderson, Natasha E. Batalha, Hannah R. Wakeford, Nicole L. Wallack, Artyom Aguichine, Johanna Teske, Jea Adams Redai, Munazza K. Alam, Natalie M. Batalha, Peter Gao, James Kirk, Mercedes Lopez-Morales, Sarah E. Moran, Nicholas Scarsdale, Nicholas F. Wogan, Angie Wolfgang

Comments: 18 pages, 7 figures, 3 tables. Accepted in the Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2404.00093 [astro-ph.EP] (or arXiv:2404.00093v1 [astro-ph.EP] for this version)
Submission history
From: Lili Alderson
[v1] Fri, 29 Mar 2024 18:01:34 UTC (2,303 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) 🖖🏻