Issue |
A&A
Volume 690, October 2024
|
|
---|---|---|
Article Number | A159 | |
Number of page(s) | 22 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202450748 | |
Published online | 08 October 2024 |
JWST reveals the rapid and strong day-side variability of 55 Cancri e
1
Department of Astronomy, Stockholm University, AlbaNova University Center,
10691
Stockholm,
Sweden
2
Weltraumforschung und Planetologie, Physikalisches Institut, Universität Bern,
Gesellschaftsstrasse 6,
3012
Bern,
Switzerland
3
Center for Space and Habitability, Universität Bern,
Gesellschaftsstrasse 6,
3012
Bern,
Switzerland
4
Observatoire astronomique de l’Université de Genève,
Chemin Pegasi 51,
1290
Versoix,
Switzerland
5
Jet Propulsion Laboratory, California Institute of Technology,
Pasadena,
CA
91011,
USA
6
Faculty of Physics, Ludwig Maximilian University,
Scheinerstrasse 1,
81679
Munich,
Bavaria,
Germany
7
ARTORG Center for Biomedical Engineering Research, University of Bern,
Murtenstrasse 50,
3008
Bern,
Switzerland
8
University College London, Department of Physics & Astronomy,
Gower St,
London
WC1E 6BT,
UK
9
University of Warwick, Department of Physics, Astronomy & Astrophysics Group,
Coventry
CV4 7AL,
UK
10
Department of Space, Earth and Environment, Chalmers University of Technology,
Onsala Space Observatory,
439 92
Onsala,
Sweden
11
Department of Astronomy and Astrophysics, The University of Chicago,
Chicago,
IL
60637,
USA
12
Centre Vie dans l’Univers, Faculté des sciences de l’Université de Genève,
Quai Ernest-Ansermet 30,
1205
Geneva,
Switzerland
13
Leiden Observatory, University of Leiden,
PO Box 9513,
2300 RA
Leiden,
The Netherlands
14
Division of Geological and Planetary Sciences, California Institute of Technology,
Pasadena,
CA
91125,
USA
15
Cavendish Laboratory,
JJ Thomson Avenue,
Cambridge
CB3 0HE,
UK
★ Corresponding author; jayshil.patel@astro.su.se
Received:
17
May
2024
Accepted:
17
July
2024
Context. The nature of the close-in rocky planet 55 Cnce is puzzling, despite it having been observed extensively. Its optical and infrared occultation depths show temporal variability, in addition to a phase curve variability observed in the optical.
Aims. We wish to explore the possibility that the variability originates from the planet being in a 3:2 spin–orbit resonance, and thus showing different sides during occultations. We proposed and were awarded Cycle 1 time at the James Webb Space Telescope (JWST) to test this hypothesis.
Methods. JWST/NIRCam (Near Infrared Camera) observed five occultations (secondary eclipses) of the planet – of which four were observed within a week – simultaneously at 2.1 and 4.5 µm. While the former gives band-integrated photometry, the latter provides a spectrum between 3.9–5.0 µm.
Results. We find that the occultation depths in both bandpasses are highly variable and change between a non-detection (−5 ± 6 ppm and 7 ± 9 ppm) to 96 ± 8 ppm and 119−19+34 ppm at 2.1 µm and 4.5 µm, respectively. Interestingly, the variations in both bandpasses are not correlated and do not support the 3:2 spin-orbit resonance explanation. The measured brightness temperature at 4.5 µm varies between 873–2256 K and is lower than the expected day-side temperature of bare rock with no heat redistribution (2500 K), which is indicative of an atmosphere. Our atmospheric retrieval analysis of occultation depth spectra at 4.5 µm finds that different visits statistically favour various atmospheric scenarios including a thin outgassed CO/CO2 atmosphere and a silicate rock vapour atmosphere. Some visits even support a flat line model.
Conclusions. The observed variability could be explained by stochastic outgassing of CO/CO2, which is also hinted at by retrievals. Alternatively, the variability observed at both 2.1 and 4.5 µm could be the result of a circumstellar patchy dust torus generated by volcanism on the planet.
Key words: techniques: photometric / techniques: spectroscopic / planets and satellites: atmospheres / planets and satellites: terrestrial planets / planets and satellites: individual: 55 Cnc e
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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