Instituto de Astrofísica e Ciências do Espaço

55 Cancri e’s occultation captured with CHEOPS

B.-O. Demory, S. Sulis, E. Meier Valdés, L. Delrez, A. Brandeker, N. Billot, A. Fortier, S. Hoyer, S. G. Sousa, K. Heng, M. Lendl, A. Krenn, B. M. Morris, J. A. Patel, Y. Alibert, R. Alonso, G. Anglada, T. Bárczy, D. Barrado, S. C. C. Barros, W. Baumjohann, M. Beck, T. Beck, W. Benz, X. Bonfils, C. Broeg, M. Buder, J. Cabrera, S. Charnoz, A. Collier Cameron, H. Cottard, S. Csizmadia, M. B. Davies, M. Deleuil, O. D. S. Demangeon, D. Ehrenreich, A. Erikson, L. Fossati, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, K. G. Isaak, L. L. Kiss, J. Laskar, A. Lecavelier Des Etangs, C. Lovis, A. Luntzer, D. Magrin, L. Marafatto, P. F. L. Maxted, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, F. Ratti, H. Rauer, I. Ribas, N. C. Santos, G. Scandariato, D. Ségransan, A. E. Simon, A. M. S. Smith, M. Steller, G. M. Szabó, N. L. Thomas, S. Udry, V. Van Grootel, N. A. Walton

Abstract

Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obtained at visible and infrared wavelengths have been challenging to reconcile with a planetary reflection and emission model. In this study, we analyse a set of 41 occultations obtained over a two-year timespan with the CHEOPS satellite. We report the detection of 55 Cnc e’s occultation with an average depth of 12 ± 3 ppm. We derive a corresponding 2σ upper limit on the geometric albedo of A_g < 0.55 once decontaminated from the thermal emission measured by Spitzer at 4.5 µm. CHEOPS’s photometric performance enables, for the first time, the detection of individual occultations of this super-Earth in the visible and identifies short-timescale photometric corrugations likely induced by stellar granulation. We also find a clear 47.3-day sinusoidal pattern in the time-dependent occultation depths that we are unable to relate to stellar noise, nor instrumental systematics, but whose planetary origin could be tested with upcoming JWST occultation observations of this iconic super-Earth.

Keywords
planets and satellites: individual: 55 Cnc e / techniques: photometric / methods: observational

Notes
- The raw and detrended photometric time-series data are available in electronic form at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/669/A64
- This article uses data from CHEOPS programme CH_PR100006.

Astronomy & Astrophysics
Volume 669, Article Number A64, Number of pages 10
2023 January

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