English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Transmission spectroscopy is enabling precise measurements of atmospheric H2Oabundances for numerous giant exoplanets. For hot Jupiters, relating H2Oabundances to metallicities provides a powerful probe of their formationconditions. However, metallicity measurements for Neptune-mass exoplanets areonly now becoming viable. Exo-Neptunes are expected to possess super-solarmetallicities from accretion of H2O-rich and solid-rich planetesimals. However,initial investigations into the exo-Neptune HAT-P-26b suggested a significantlylower metallicity than predicted by the core-accretion theory of planetaryformation and solar system expectations from Uranus and Neptune. Here, wereport an extensive atmospheric retrieval analysis of HAT-P-26b, combining allavailable observations, to reveal its composition, temperature structure, andcloud properties. Our analysis reveals an atmosphere containing1.5(+2.1)(-0.9)% H2O, an O/H of 18.1(+25.9)(-11.3)x solar, and C/O < 0.33 (to2$\sigma$). This updated metallicity, the most precise exo-Neptune metallicityreported to date, suggests a formation history with significant planetesimalaccretion, albeit below that of Uranus and Neptune. We additionally reportevidence for metal hydrides at 4.1$\sigma$ confidence. Potential candidates areidentified as TiH (3.6$\sigma$), CrH (2.1$\sigma$), or ScH (1.8$\sigma$).Maintaining gas-phase metal hydrides at the derived temperature (~560 K)necessitates strong disequilibrium processes or external replenishment.Finally, we simulate the JWST Guaranteed Time Observations for HAT-P-26b.Assuming a composition consistent with current observations, we predict JWSTcan detect H2O (at 29$\sigma$), CH4 (6.2$\sigma$), CO2 (13$\sigma$), and CO(3.7$\sigma$), improving metallicity and C/O precision to 0.2 dex and 0.35 dex.Furthermore, NIRISS observations could detect several metal hydrides at>5$\sigma$ confidence.

The Metal-Rich Atmosphere of the Neptune HAT-P-26b