Possible Carbon Dioxide above the Thick Aerosols of GJ 1214 b

October 2024 • 2024ApJ...974L..33S

Authors • Schlawin, Everett • Ohno, Kazumasa • Bell, Taylor J. • Murphy, Matthew M. • Welbanks, Luis • Beatty, Thomas G. • Greene, Thomas P. • Fortney, Jonathan J. • Parmentier, Vivien • Edelman, Isaac R. • Gill, Samuel • Anderson, David R. • Wheatley, Peter J. • Henry, Gregory W. • Mehta, Nishil • Kreidberg, Laura • Rieke, Marcia J.

Abstract • Sub-Neptune planets with radii smaller than Neptune (3.9 R _⊕) are the most common type of planet known to exist in the Milky Way, even though they are absent in the solar system. These planets can potentially have a large diversity of compositions as a result of different mixtures of rocky material, icy material, and gas accreted from a protoplanetary disk. However, the bulk density of a sub-Neptune, informed by its mass and radius alone, cannot uniquely constrain its composition; atmospheric spectroscopy is necessary. GJ 1214 b, which hosts an atmosphere that is potentially the most favorable for spectroscopic detection of any sub-Neptune, is instead enshrouded in aerosols (thus showing no spectroscopic features), hiding its composition from view at previously observed wavelengths in its terminator. Here, we present a JWST NIRSpec transmission spectrum from 2.8 to 5.1 μm that shows signatures of CO₂ and CH₄, expected at high metallicity. A model containing both these molecules is preferred by 3.3σ and 3.6σ as compared to a featureless spectrum for two different data analysis pipelines, respectively. Given the low signal-to-noise of the features compared to the continuum, however, more observations are needed to confirm the CO₂ and CH₄ signatures and better constrain other diagnostic features in the near-infrared. Further modeling of the planet's atmosphere, interior structure and origins will provide valuable insights about how sub-Neptunes like GJ 1214 b form and evolve.

Links

• PREPRINT http://arxiv.org/abs/2410.10183
• ELECTR https://doi.org/10.3847/2041-8213/ad7fef
• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2024ApJ...974L..33S
• PDF https://iopscience.iop.org/article/10.3847/2041-8213/ad7fef/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2024ApJ...974L..33S
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2024ApJ...974L..33S
• DATA https://doi.org/10.17909/tqa7-th94
• DATA https://doi.org/10.5281/zenodo.13787956