A Revisit of the Mass–Metallicity Trends in Transiting Exoplanets

• Published in: The Astronomical journal 2024-04, Vol.167 (4), p.167
• Main Authors: Sun, Qinghui, Wang, Sharon Xuesong, Welbanks, Luis, Teske, Johanna, Buchner, Johannes
• Format: Article
• Language: English
• Subjects: Abundance; Accretion disks; Correlation; Exoplanet astronomy; Exoplanet atmospheres; Exoplanet formation; Extrasolar planets; Gas giant planets; High resolution; Hubble Space Telescope; James Webb Space Telescope; Metallicity; Monte Carlo simulation; Planet formation; Planet hosting stars; Planetary atmospheres; Planetary mass; Planets; Space telescopes; Stars; Transit; Trends
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/ad298d

The two prevailing planet formation scenarios, core accretion and disk instability, predict distinct planetary mass–metallicity relations. Yet, the detection of this trend remains challenging due to inadequate data on planet atmosphere abundance and inhomogeneities in both planet and host stellar abundance measurements. Here we analyze high-resolution spectra for the host stars of 19 transiting exoplanets to derive the C, O, Na, S, and K abundances, including planetary types from cool mini-Neptunes to hot Jupiters ( T eq ∼ 300–2700 K; planet radius ∼0.1–2 R J ). Our Monte Carlo simulations suggest that the current data set, updated based on Welbanks et al., is unable to distinguish between a linear relation and an independent distribution model for the abundance-mass correlation for water, Na, or K. To detect a trend with strong evidence (Bayes factor > 10) at the 2 σ confidence interval, we recommend a minimum sample of 58 planets with Hubble Space Telescope measurements of water abundances coupled with [O/H] of the host stars, or 45 planets at the JWST precision. Coupled with future JWST or ground-based high-resolution data, this well-characterized sample of planets with precise host-star abundances constitute an important ensemble of planets to further probe the abundance-mass correlation.