Detection of Carbon Monoxide’s 4.6 Micron Fundamental Band Structure in WASP-39b’s Atmosphere with JWST NIRSpec G395H
/ Authors
D. Grant, J. Lothringer, H. Wakeford, M. Alam, L. Alderson, J. Bean, B. Benneke, Jean-Michel D'esert, T. Daylan, L. Flagg
and 21 more authors
R. Hu, J. Inglis, J. Kirk, L. Kreidberg, M. L'opez-Morales, L. Mancini, T. Mikal-Evans, K. Molaverdikhani, E. Pallé, B. Rackham, S. Redfield, K. Stevenson, J. Valenti, N. Wallack, K. Aggarwal, E. Ahrer, I. Crossfield, N. Crouzet, N. Iro, N. Nikolov, P. Wheatley
/ Abstract
Carbon monoxide (CO) is predicted to be the dominant carbon-bearing molecule in giant planet atmospheres and, along with water, is important for discerning the oxygen and therefore carbon-to-oxygen ratio of these planets. The fundamental absorption mode of CO has a broad, double-branched structure composed of many individual absorption lines from 4.3 to 5.1 μm, which can now be spectroscopically measured with JWST. Here we present a technique for detecting the rotational sub-band structure of CO at medium resolution with the NIRSpec G395H instrument. We use a single transit observation of the hot Jupiter WASP-39b from the JWST Transiting Exoplanet Community Early Release Science (JTEC ERS) program at the native resolution of the instrument (R ∼ 2700) to resolve the CO absorption structure. We robustly detect absorption by CO, with an increase in transit depth of 264 ± 68 ppm, in agreement with the predicted CO contribution from the best-fit model at low resolution. This detection confirms our theoretical expectations that CO is the dominant carbon-bearing molecule in WASP-39b’s atmosphere and further supports the conclusions of low C/O and supersolar metallicities presented in the JTEC ERS papers for WASP-39b.
Journal: The Astrophysical Journal Letters