Exoplanets & Exomoons

The Transmission Spectrum Of The Potentially Rocky Planet L 98-59 c

By Keith Cowing
Status Report
February 1, 2023
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The Transmission Spectrum Of The Potentially Rocky Planet L 98-59 c
The heat maps above portray the results of a two molecule atmosphere analysis. All of the presented analyses have the molecule CO2 on the y-axis. In the top left we have CH4, in the top middle we have CO, in the top right we have H2O, in the bottom left we have H2S, in the bottom middle we have NH3, and in the bottom right we have HCN. All molecules have been presented in the volume mixing ratio. We retrieved for diameter at each abundance level, and calculated the reduced χ 2 to find the best fit retrieval for diameter. — astro-ph.EP

We present observations of the 1.35+/-0.07 Earth-radius planet L 98-59 c using Wide Field Camera~3 on the Hubble Space Telescope. L 98-59 is a nearby (10.6 pc), bright (H=7.4 mag), M3V star that harbors three small, transiting planets.

As one of the closest known transiting multi-planet systems, L 98-59 offers one of the best opportunities to probe and compare the atmospheres of rocky planets that formed in the same stellar environment. We measured the transmission spectrum of L 98-59 c during a single transit, with the extracted spectrum showing marginal evidence for wavelength-dependent transit depth variations which would indicate the presence of an atmosphere.

Forward modeling was used to constrain possible atmospheric compositions of the planet based on the shape of the transmission spectrum. Although L 98-59 is a fairly quiet star, we have seen evidence for stellar activity, and therefore we cannot rule out a scenario where the source of the signal originates with inhomogeneities on the host-star surface. While intriguing, our results are inconclusive and additional data is needed to verify any atmospheric signal.

Fortunately, additional data will soon be collected from both HST and JWST. Should this result be confirmed with additional data, L 98-59 c would be the first planet smaller than 2 Earth-radii with a detected atmosphere, and among the first small planets with a known atmosphere to be studied in detail by the JWST.

Thomas Barclay, Kyle B. Sheppard, Natasha Latouf, Avi M. Mandell, Elisa V. Quintana, Emily A. Gilbert, Giuliano Liuzzi, Geronimo L. Villanueva, Giada Arney, Jonathan Brande, Knicole D. Colón, Giovanni Covone, Ian J.M. Crossfield, Mario Damiano, Shawn D. Domagal-Goldman, Thomas J. Fauchez, Stefano Fiscale, Francesco Gallo, Christina L. Hedges, Renyu Hu, Edwin S. Kite, Daniel Koll, Ravi K. Kopparapu, Veselin B. Kostov, Laura Kreidberg, Eric D. Lopez, James Mang, Caroline V. Morley, Fergal Mullally, Susan E. Mullally, Daria Pidhorodetska, Joshua E. Schlieder, Laura D. Vega, Allison Youngblood, Sebastian Zieba

Comments: Submitted to AAS Journals
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2301.10866 [astro-ph.EP] (or arXiv:2301.10866v1 [astro-ph.EP] for this version)
Submission history
From: Thomas Barclay
[v1] Wed, 25 Jan 2023 23:21:37 UTC (11,535 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) 🖖🏻