JWST COMPASS: NIRSpec/G395H Transmission Observations of the Super-Earth TOI-836b
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)
https://arxiv.org/abs/2404.00093
Astrobiology
