Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H
Creators: name: Alderson, Lili
name: Wakeford, Hannah R.
name: Alam, Munazza K.
name: Batalha, Natasha E.
name: Lothringer, Joshua D.
name: Redai, Jea Adams
name: Barat, Saugata
name: Brande, Jonathan
name: Damiano, Mario
name: Daylan, Tansu
name: Espinoza, Néstor
name: Flagg, Laura
name: Goyal, Jayesh M.
name: Grant, David
name: Hu, Renyu
name: Inglis, Julie
name: Lee, Elspeth K. H.
name: Mikal-Evans, Thomas
name: Ramos-Rosado, Lakeisha
name: Roy, Pierre-Alexis
name: Wallack, Nicole L.
name: Batalha, Natalie M.
name: Bean, Jacob L.
name: Benneke, Björn
name: Berta-Thompson, Zachory K.
name: Carter, Aarynn L.
name: Changeat, Quentin
name: Colón, Knicole D.
name: Crossfield, Ian J. M.
name: Désert, Jean-Michel
name: Foreman-Mackey, Daniel
name: Gibson, Neale P.
name: Kreidberg, Laura
name: Line, Michael R.
name: López-Morales, Mercedes
name: Molaverdikhani, Karan
name: Moran, Sarah E.
name: Morello, Giuseppe
name: Moses, Julianne I.
name: Mukherjee, Sagnick
name: Schlawin, Everett
name: Sing, David K.
name: Stevenson, Kevin B.
name: Taylor, Jake
name: Aggarwal, Keshav
name: Ahrer, Eva-Maria
name: Allen, Natalie H.
name: Barstow, Joanna K.
name: Bell, Taylor J.
name: Blecic, Jasmina
name: Casewell, Sarah L.
name: Chubb, Katy L.
name: Crouzet, Nicolas
name: Cubillos, Patricio E.
name: Decin, Leen
name: Feinstein, Adina D.
name: Fortney, Joanthan J.
name: Harrington, Joseph
name: Heng, Kevin
name: Iro, Nicolas
name: Kempton, Eliza M. -R.
name: Kirk, James
name: Knutson, Heather A.
name: Krick, Jessica
name: Leconte, Jérémy
name: Lendl, Monika
name: MacDonald, Ryan J.
name: Mancini, Luigi
name: Mansfield, Megan
name: May, Erin M.
name: Mayne, Nathan J.
name: Miguel, Yamila
name: Nikolov, Nikolay K.
name: Ohno, Kazumasa
name: Palle, Enric
name: Parmentier, Vivien
name: de la Roche, Dominique J. M. Petit dit
name: Piaulet, Caroline
name: Powell, Diana
name: Rackham, Benjamin V.
name: Redfield, Seth
name: Rogers, Laura K.
name: Rustamkulov, Zafar
name: Tan, Xianyu
name: Tremblin, P.
name: Tsai, Shang-Min
name: Turner, Jake D.
name: de Val-Borro, Miguel
name: Venot, Olivia
name: Welbanks, Luis
name: Wheatley, Peter J.
name: Zhang, Xi
Publisher: name: arXiv
Year: 2022
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems. Access to an exoplanet's chemical inventory requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based and high-resolution ground-based facilities. Here we report the medium-resolution (R$\sim$600) transmission spectrum of an exoplanet atmosphere between 3-5 $μ$m covering multiple absorption features for the Saturn-mass exoplanet WASP-39b, obtained with JWST NIRSpec G395H. Our observations achieve 1.46x photon precision, providing an average transit depth uncertainty of 221 ppm per spectroscopic bin, and present minimal impacts from systematic effects. We detect significant absorption from CO$_2$ (28.5$σ$) and H$_2$O (21.5$σ$), and identify SO$_2$ as the source of absorption at 4.1 $μ$m (4.8$σ$). Best-fit atmospheric models range between 3 and 10x solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO$_2$, underscore the importance of characterising the chemistry in exoplanet atmospheres, and showcase NIRSpec G395H as an excellent mode for time series observations over this critical wavelength range.
description: 44 pages, 11 figures, 3 tables. Resubmitted after revision to Nature