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JWST COMPASS: The 3-5 Micron Transmission Spectrum of the Super-Earth L 98-59 c

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arxiv 2409.07552 v1 pith:SSBVAPKT submitted 2024-09-11 astro-ph.EP

classification astro-ph.EP
keywords atmospheresatmosphericoplusrulespectrumtransmissionbelowdata
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

We present a JWST NIRSpec transmission spectrum of the super-Earth exoplanet L 98-59 c. This small (R$_p=1.385\pm0.085$R$_\oplus$, M$_p=2.22\pm0.26$R$_\oplus$), warm (T$_\textrm{eq}=553$K) planet resides in a multi-planet system around a nearby, bright (J = 7.933) M3V star. We find that the transmission spectrum of L 98-59 c is featureless at the precision of our data. We achieve precisions of 22ppm in NIRSpec G395H's NRS1 detector and 36ppm in the NRS2 detector at a resolution R$\sim$200 (30 pixel wide bins). At this level of precision, we are able rule out primordial H$_2$-He atmospheres across a range of cloud pressure levels up to at least $\sim$0.1mbar. By comparison to atmospheric forward models, we also rule out atmospheric metallicities below $\sim$300$\times$ solar at 3$\sigma$ (or equivalently, atmospheric mean molecular weights below $\sim$10~g/mol). We also rule out pure methane atmospheres. The remaining scenarios that are compatible with our data include a planet with no atmosphere at all, or higher mean-molecular weight atmospheres, such as CO$_2$- or H$_2$O-rich atmospheres. This study adds to a growing body of evidence suggesting that planets $\lesssim1.5$R$_\oplus$ lack extended atmospheres.

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Forward citations

Cited by 7 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e

    astro-ph.EP 2025-09 conditional novelty 7.0 of 10

    Using four JWST/NIRSpec PRISM transits and a new Gaussian Process retrieval that marginalizes over stellar contamination, the authors rule out cloudy, H2-dominated (≳80% by volume) primary atmospheres on TRAPPIST-1 e at >3σ.

  2. Pyrat Bay 2.0: an Upgraded Framework for Exoplanet Atmosphere Modeling in the JWST Era

    astro-ph.EP 2026-08 conditional novelty 6.0 of 10

    Pyrat Bay 2.0 adds equilibrium chemistry, radiative equilibrium, and vertically varying abundance retrieval, and simulations indicate JWST-quality spectra can recover such variations.

  3. Sulfur photochemistry observationally traces mantle redox states of rocky planets

    astro-ph.EP 2026-07 conditional novelty 6.0 of 10

    Photochemical SO2 in rocky exoplanet atmospheres produces JWST-detectable absorption features at 4 and 7–9 μm that trace the mantle's oxidation state, linking observed spectra to planetary interiors.

  4. JWST COMPASS: A NIRSpec G395H Transmission Spectrum of the Super-Earth GJ 357 b

    astro-ph.EP 2025-07 conditional novelty 5.0 of 10

    The first NIRSpec G395H transmission spectrum of GJ 357 b is featureless, ruling out low mean molecular weight atmospheres at 3-sigma and pointing to a bare rock or a high molecular weight secondary atmosphere.

  5. JWST NIRISS Transmission Spectroscopy of the Super-Earth GJ 357b, a Favourable Target for Atmospheric Retention

    astro-ph.EP 2025-05 conditional novelty 5.0 of 10

    The first JWST transmission spectrum of GJ 357b is featureless, ruling out low-metallicity atmospheres up to about 100 times solar and motivating follow-up observations.

  6. JWST COMPASS: NIRSpec/G395H Transmission Observations of the Super-Earth TOI-776b

    astro-ph.EP 2025-01 conditional novelty 4.0 of 10

    JWST transmission spectra of the super-Earth TOI-776b are flat, ruling out low-metallicity hydrogen atmospheres below about 100 times solar metallicity at a pressure of 1 millibar.

  7. A first look at rocky exoplanets with JWST

    astro-ph.EP 2025-07 accept novelty 3.0 of 10

    This review of JWST rocky exoplanet observations finds no confirmed atmospheres and sets a five scale height precision target for future transmission spectroscopy.

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