Exoplanets & Exomoons

Investigating The Visible Phase Curve Variability Of 55 Cnc e

By Keith Cowing
Status Report
July 13, 2023
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Investigating The Visible Phase Curve Variability Of 55 Cnc e
Detrended flux measurements of 55 Cnc e, phase-folded at the planet orbital period. The top panel shows the relative flux, while the bottom panel presents the residuals in ppm. The plots show a portion of the phase centred around the transit. Red squares represent binned data. — astro-ph.EP

55 Cnc e is an ultra-short period super-Earth transiting a Sun-like star. Past observations in the optical range detected a time-variable flux modulation phased with the planetary orbital period whose amplitude is too large to be explained by reflected light and thermal emission alone.

The goal of the study is to investigate the origin of the variability and timescale of 55 Cnc e’s phase curve modulation. To that end, we used the CHaracterising ExOPlanet Satellite (CHEOPS) whose exquisite photometric precision provides an opportunity to characterise minute changes in the phase curve from orbit to orbit. CHEOPS observed 29 individual visits of 55 Cnc e between March 2020 and February 2022.

Based on these observations, we investigate the different processes that could be at the origin of the observed modulation. In particular, we build a toy model to assess whether a circumstellar torus of dust driven by radiation pressure and gravity could match the observed flux variability timescale. We find that 55 Cnc e’s phase curve amplitude and peak offset do vary between visits. The sublimation timescales of selected dust species reveal that silicates expected in an Earth-like mantle would not survive long enough to explain the observed phase curve modulation.

We find that silicon carbide, quartz and graphite are plausible candidates for the circumstellar torus composition due to their long sublimation timescales. The extensive CHEOPS observations confirm that the phase curve amplitude and offset vary in time. We find that dust could provide the grey opacity source required to match the observations. However, the data at hand do not provide evidence that circumstellar material with variable grain mass per unit area is actually causing the observed variability. Future observations with JWST promise exciting insights on this iconic super-Earth.

E. A. Meier Valdés, B. M. Morris, B.-O. Demory, A. Brandeker, D. Kitzmann, W. Benz, A. Deline, H.-G. Florén, S. G. Sousa, V. Bourrier, V. Singh, K. Heng, A. Strugarek, D. J. Bower, N. Jäggi, L. Carone, M. Lendl, K. Jones, A. V. Oza, O. D. S. Demangeon, Y. Alibert, R. Alonso, G. Anglada, J. Asquier, T. Bárczy, D. Barrado Navascues, S. C. C. Barros, W. Baumjohann, M. Beck, T. Beck, N. Billot, X. Bonfils, L. Borsato, C. Broeg, J. Cabrera, S. Charnoz, A. Collier Cameron, Sz. Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, L. Delrez, D. Ehrenreich, A. Erikson, A. Fortier, L. Fossati, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, M. N. Günther, S. Hoyer, K. G. Isaak, L. L. Kiss, J. Laskar, A. Lecavelier des Etangs, C. Lovis, D. Magrin, P. F. L. Maxted, C. Mordasini, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, M. Sarajlic, G. Scandariato, D. Ségransan, D. Sicilia, A. E. Simon, A. M. S. Smith, M. Steller, Gy. M. Szabó, N. Thomas, S. Udry, B. Ulmer, V. Van Grootel, J. Venturini, N. A. Walton, T. G. Wilson, D. Wolter

Comments: 27 pages, 22 figures. Accepted for publication on A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2307.06085 [astro-ph.EP] (or arXiv:2307.06085v1 [astro-ph.EP] for this version)
Submission history
From: Erik Andreas Meier Valdés
[v1] Wed, 12 Jul 2023 11:15:13 UTC (28,636 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻