KRONOS I: The 1–2.8 μ m JWST Transmission Spectrum of the 23 Myr V1298 Tau c

2026/06/02 by Matthew M. Murphy, Matthew C. Nixon, Adina D. Feinstein +19 · 1 voice · 1 citation
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Exoplanet #Grism #Metallicity #Occultation #Planet #Planetary system #Spectrograph #Stars #Stellar, planetary, and galactic studies #Transit (satellite) #astro-ph.EP #astro-ph.SR

paper · pdf · open access · doi:10.3847/1538-3881/ae7a32

published in The Astronomical Journal 172(1), 66 (Institute of Physics)

openalex publication_date 2026/07/01 · openalex created_date 2026/07/02 · openalex updated_date 2026/08/05

Abstract

Abstract While recent JWST observations of mature super-Earths and sub-Neptunes have frequently revealed featureless transmission spectra, their inflated progenitors offer a unique window into understanding their primordial compositions. As part of the Keys to Revealing the Origin and Nature of Sub-Neptune Systems (KRONOS) JWST program, we present the Near Infrared Imager and Slitless Spectrograph Single Object Slitless Spectroscopy transmission spectrum of V1298 Tau c, an ∼23 Myr super-Earth progenitor orbiting a young solar analog. We detect H 2 O in V1298 Tau c’s atmosphere with a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> </mml:math> volume mixing ratio of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>−</mml:mo> <mml:mn>1.8</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.77</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.68</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , but no additional molecules from these data alone. We find consistent results for the planetary atmospheric properties in both retrievals with and without informed priors on stellar heterogeneities based on the observed stellar spectrum. We infer an atmospheric metallicity [O/H] of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>14</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>12.28</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>56.0</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> </mml:math> the solar value. This metallicity is similar to literature measurements for other young planets, including its massive outer companion V1298 Tau b. In contrast, this measured metallicity is systematically lower than the metallicities of mature planets of similar mass and temperature. Altogether, these results provide tentative but growing evidence that the exoplanet mass–metallicity relation evolves with planetary age.

Citations

• NASA’s Pandora SmallSat Mission: Simulating the Impact of Stellar Photospheric Heterogeneity and Its Correction
• NASA’s Pandora SmallSat Mission: Simulated Modeling and Retrieval of Near-infrared Exoplanet Transmission Spectra
• JWST COMPASS: A NIRSpec G395H Transmission Spectrum of Radius Valley-Dweller TOI-260 b
• Combined Exoplanet Mass and Atmospheric Characterization for Accelerated Exoplanetology
• A Thick Volatile Atmosphere on the Ultrahot Super-Earth TOI-561 b
• Overcast mornings and clear evenings in hot Jupiter exoplanet atmospheres
• The SPACE Program. I. The featureless spectrum of HD 86226 c challenges sub-Neptune atmosphere trends
• Insufficient evidence for DMS and DMDS in the atmosphere of K2-18 b
• TESS Investigation -- Demographics of Young Exoplanets (TI-DYE) III: an inner super-Earth in TOI-2076
• Challenges in the detection of gases in exoplanet atmospheres
• A Comprehensive Reanalysis of K2-18 b's JWST NIRISS+NIRSpec Transmission Spectrum
• The Featherweight Giant: Unraveling the Atmosphere of a 17 Myr Planet with JWST
• Axisymmetric High Spot Coverage on Exoplanet Host HD 189733 A
• Carbon-bearing Molecules in a Possible Hycean Atmosphere
• The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope. I. Instrument Overview and In-flight Performance
• Toward Robust Corrections for Stellar Contamination in JWST Exoplanet Transmission Spectra
• The Transit Light Source Effect II: The Impact of Stellar Heterogeneity on Transmission Spectra of Planets Orbiting Broadly Sun-like Stars
• batman: BAsic Transit Model cAlculatioN in Python
• emcee: The MCMC Hammer
• HITEMP, the high-temperature molecular spectroscopic database
• The Chemical Composition of the Sun
• Cloudy mornings and clear evenings on a gas giant exoplanet
• Quantifying the Impact of Starspot-crossing Events on Retrieved Parameters from Transit Lightcurves

Cited by

• KRONOS II: Solar-like Umbra and Penumbra Properties on the Young Sun V1298~Tau

Discussions

• after a wild ride, I am so so so excited to have the first paper of our JWST KRONOS program out! "KRONOS I: The 1−2.8µm JWST Transmission Spectrum of the 23 Myr V1298 Tau c" led by MSU postdoc Matthew [bsky, 29 points, 1 comments]

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