A precise metallicity and carbon-to-oxygen ratio for a warm giant exoplanet from its panchromatic JWST emission spectrum

• 成果类型: Article
• 署名作者: Wiser, Lindsey S.; Bell, Taylor J.; Line, Michael R.; Schlawin, Everett; Beatty, Thomas G.; Welbanks, Luis; Greene, Thomas P.; Parmentier, Vivien; Murphy, Matthew M.; Fortney, Jonathan J.; Arnold, Kenny; Mehta, Nishil; Ohno, Kazumasa; Mukherjee, Sagnick
• 署名单位: Arizona State University; Arizona State University-Tempe; National Aeronautics & Space Administration (NASA); NASA Ames Research Center; National Aeronautics & Space Administration (NASA); NASA Ames Research Center; Space Telescope Science Institute; University of Arizona; University of Wisconsin System; University of Wisconsin Madison; Universite Cote d'Azur; Observatoire de la Cote d'Azur; University of California System; University of California Santa Cruz; National Institutes of Natural Sciences (NINS) - Japan; National Astronomical Observatory of Japan (NAOJ)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-13528
• DOI: 10.1073/pnas.2416193122
• 发表日期: 2025-09-30
• 关键词: planet formation; mass; enrichment; atmosphere; dayside; MODEL

摘要

WASP-80 b, a warm sub-Jovian (equilibrium temperature similar to 820 K, 0.5 Jupiter masses), presents an opportunity to characterize a rare gas giant exoplanet around a low-mass star. In addition, its moderate temperature enables its atmosphere to host a range of carbon and oxygen species (H2O, CH4, CO, CO2, NH3). In this paper, we present a panchromatic emission spectrum of WASP-80 b, the first gas giant around a late K/early M-dwarf star and the coolest planet for which the James Webb Space Telescope has obtained a complete emission spectrum spanning 2.4 to 12 mu m, including NIRCam F322W2 (2.4 to 4 mu m) and F444W (4 to 5 mu m), and MIRI LRS (5 to 12 mu m). We report confident detections of H2O, CH4, CO, and CO2, and a tentative detection of NH3. We estimate WASP-80 b's atmospheric metallicity and carbon-to-oxygen ratio and compare them with estimates for other gas giants. Despite the relative rarity of giant planets around low-mass stars, we find that WASP-80 b's composition is consistent with other hot gas giants, suggesting that the formation pathway of WASP-80 b may not be dissimilar from hot gas giants around higher-mass stars.