First unambiguous detection of ammonia in the atmosphere of a planetary mass companion with JWST/MIRI coronagraphs

Context . The newly accessible mid-infrared (MIR) window offered by the James Webb Space Telescope (JWST) for exoplanet imaging is expected to provide valuable information to characterize their atmospheres. In particular, coronagraphs on board the JWST Mid-InfraRed instrument (MIRI) are capable of imaging the coldest directly imaged giant planets at the wavelengths where they emit most of their flux. The MIRI coronagraphs have been specially designed to detect the NH 3 absorption around 10.5 µm, which has been predicted by atmospheric models and should be detectable for planets colder than 1200 K. Aims . We aim to assess the presence of NH 3 while refining the atmospheric parameters of one of the coldest companions detected by directly imaging GJ 504 b. Its mass is still a matter of debate and depending on the host star age estimate, the companion could either be placed in the brown dwarf regime of ∼20 M Jup or in the young Jovian planet regime of ∼4 M Jup . Methods . We present an analysis of new MIRI observations, using the coronagraphic filters F1065C, F1140C, and F1550C of the GJ 504 system. We took advantage of previous observations of reference stars to build a library of images and to perform a more efficient subtraction of the stellar diffraction pattern. We used an atmospheric grid from the Exo-REM model to refine the atmospheric parameters by combining archival near-infrared (NIR) photometry with the MIR photometry. Results . We detected the presence of NH 3 at 12.5 σ and measured its volume mixing ratio of 10 −5.3±0.07 in the atmosphere of GJ 504 b. These results are in line with atmospheric model expectations for a planetary-mass object and observed in brown dwarfs within a similar temperature range. The best-fit model with Exo-REM provides updated values of its atmospheric parameters, yielding a temperature of T eff = 512 ± 10 K and radius of R = 1.08 −0.03 +0.04 R Jup . Conclusions . These observations demonstrate the capability of MIRI coronagraphs to detect NH 3 and to provide the first MIR observations of one of the coldest directly imaged companions. Overall, NH 3 is a key molecule for characterizing the atmospheres of cold planets, offering valuable insights into their surface gravity. These observations provide valuable information for future spectroscopic observations planned with JWST, in particular, with the MIRI medium-resolution spectrometer (MRS), which will allow us to characterize the atmosphere of GJ 504 b in depth.

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Journal
Astronomy and Astrophysics
Published
2024-12-31
DOI
https://doi.org/10.1051/0004-6361/202452695
Citations
8
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
2.65

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article

First unambiguous detection of ammonia in the atmosphere of a planetary mass companion with JWST/MIRI coronagraphs

Alistair Glasse, M. Guêdel, Élodie Choquet, Adrian M. Glauser et al.
8 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
2.65
article

First unambiguous detection of ammonia in the atmosphere of a planetary mass companion with JWST/MIRI coronagraphs

Alistair Glasse, M. Guêdel, Élodie Choquet, Adrian M. Glauser, Pascal Tremblin, Niall Whiteford, Rens Waters, Göran Östlin, Benjamin Charnay, E. F. van Dishoeck, L. Decin, T. P. Ray, Christophe Cossou, Pierre Baudoz, Silvia Scheithauer, Olivier Absil, Mathilde Mâlin, J. P. Pye, C. Perrot, D. Barrado, Polychronis Patapis, Daniel Rouan, Camilla Danielski, G. Olofsson, Thomas Henning, A. Boccaletti, P. Royer, B. Vandenbussche, Gillian Wright, Pierre-Olivier Lagage, Eugene Serabyn
article en
8 citations

Abstract

Context . The newly accessible mid-infrared (MIR) window offered by the James Webb Space Telescope (JWST) for exoplanet imaging is expected to provide valuable information to characterize their atmospheres. In particular, coronagraphs on board the JWST Mid-InfraRed instrument (MIRI) are capable of imaging the coldest directly imaged giant planets at the wavelengths where they emit most of their flux. The MIRI coronagraphs have been specially designed to detect the NH 3 absorption around 10.5 µm, which has been predicted by atmospheric models and should be detectable for planets colder than 1200 K. Aims . We aim to assess the presence of NH 3 while refining the atmospheric parameters of one of the coldest companions detected by directly imaging GJ 504 b. Its mass is still a matter of debate and depending on the host star age estimate, the companion could either be placed in the brown dwarf regime of ∼20 M Jup or in the young Jovian planet regime of ∼4 M Jup . Methods . We present an analysis of new MIRI observations, using the coronagraphic filters F1065C, F1140C, and F1550C of the GJ 504 system. We took advantage of previous observations of reference stars to build a library of images and to perform a more efficient subtraction of the stellar diffraction pattern. We used an atmospheric grid from the Exo-REM model to refine the atmospheric parameters by combining archival near-infrared (NIR) photometry with the MIR photometry. Results . We detected the presence of NH 3 at 12.5 σ and measured its volume mixing ratio of 10 −5.3±0.07 in the atmosphere of GJ 504 b. These results are in line with atmospheric model expectations for a planetary-mass object and observed in brown dwarfs within a similar temperature range. The best-fit model with Exo-REM provides updated values of its atmospheric parameters, yielding a temperature of T eff = 512 ± 10 K and radius of R = 1.08 −0.03 +0.04 R Jup . Conclusions . These observations demonstrate the capability of MIRI coronagraphs to detect NH 3 and to provide the first MIR observations of one of the coldest directly imaged companions. Overall, NH 3 is a key molecule for characterizing the atmospheres of cold planets, offering valuable insights into their surface gravity. These observations provide valuable information for future spectroscopic observations planned with JWST, in particular, with the MIRI medium-resolution spectrometer (MRS), which will allow us to characterize the atmosphere of GJ 504 b in depth.

Astronomy and AstrophysicsVol. 693
Leiden University (NL), Space Telescope Science Institute (US), Dublin Institute For Advanced Studies (IE), Jet Propulsion Laboratory (US), Johns Hopkins University (US), University of Leicester (GB), University of Liège (BE), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), ETH Zurich (CH), Astrophysique, Instrumentation et Modélisation (FR), Laboratoire d’Astrophysique de Marseille (FR), Institute of Particle Physics (CA), Royal Observatory (GB), Max Planck Institute for Astronomy (DE), Château Gombert (FR), Laboratoire d’études spatiales et d’instrumentation en astrophysique (FR), Institute of Astronomy (RU), CEA Paris-Saclay (FR), Centro de Astrobiología (ES), Central Park Conservancy (US), AlbaNova (SE), Institut de Recherche sur les Lois Fondamentales de l'Univers (FR), Leiden Observatory, LIRA - Laboratoire d'instrumentation et de recherche en astrophysique (FR), National Institute for Astrophysics (IT)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Space Telescope Science Institute, European Space Agency, European Commission, National Research Foundation, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Danmarks Grundforskningsfond, Swedish National Space Agency, Fonds De La Recherche Scientifique - FNRS, Belgian Federal Science Policy Office, Centre National d’Etudes Spatiales, Fonds Wetenschappelijk Onderzoek, KU Leuven, Knut och Alice Wallenbergs Stiftelse, Max-Planck-Institut für Astronomie, Jet Propulsion Laboratory, Horizon 2020 Framework Programme, Science and Technology Facilities Council, Agencia Estatal de Investigación
Openalex Percentile: Top 10%
Stellar, planetary, and galactic studies
2.65
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