Investigating the visible phase-curve variability of 55 Cnc e
Abstract
55 Cnc e is an ultra-short period super-Earth transiting a Sun-like star. Previous observations in the optical range detected a time-variable flux modulation that is 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 the phase-curve modulation in 55 Cnc e. To this end, we used the CHaracterising ExOPlanet Satellite (CHEOPS), whose exquisite photometric precision provides an opportunity to characterise minute changes in the phase curve from one orbit to the next. CHEOPS observed 29 individual visits of 55 Cnc e between March 2020 and February 2022. Based on these observations, we investigated the different processes that could be at the origin of the observed modulation. In particular, we built a toy model to assess whether a circumstellar torus of dust driven by radiation pressure and gravity might match the observed flux variability timescale. We find that the phase-curve amplitude and peak offset of 55 Cnc e 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 because their sublimation timescales are long. 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 a variable grain mass per unit area causes the observed variability. Future observations with the James Webb Space Telescope promise exciting insights into this iconic super-Earth.
Keywords
Cite
@article{arxiv.2307.06085,
title = {Investigating the visible phase-curve variability of 55 Cnc e},
author = {E. A. Meier Valdés and B. M. Morris and B. -O. Demory and A. Brandeker and D. Kitzmann and W. Benz and A. Deline and H. -G. Florén and S. G. Sousa and V. Bourrier and V. Singh and K. Heng and A. Strugarek and D. J. Bower and N. Jäggi and L. Carone and M. Lendl and K. Jones and A. V. Oza and O. D. S. Demangeon and Y. Alibert and R. Alonso and G. Anglada and J. Asquier and T. Bárczy and D. Barrado Navascues and S. C. C. Barros and W. Baumjohann and M. Beck and T. Beck and N. Billot and X. Bonfils and L. Borsato and C. Broeg and J. Cabrera and S. Charnoz and A. Collier Cameron and Sz. Csizmadia and P. E. Cubillos and M. B. Davies and M. Deleuil and L. Delrez and D. Ehrenreich and A. Erikson and A. Fortier and L. Fossati and M. Fridlund and D. Gandolfi and M. Gillon and M. Güdel and M. N. Günther and S. Hoyer and K. G. Isaak and L. L. Kiss and J. Laskar and A. Lecavelier des Etangs and C. Lovis and D. Magrin and P. F. L. Maxted and C. Mordasini and V. Nascimbeni and G. Olofsson and R. Ottensamer and I. Pagano and E. Pallé and G. Peter and G. Piotto and D. Pollacco and D. Queloz and R. Ragazzoni and N. Rando and H. Rauer and I. Ribas and N. C. Santos and M. Sarajlic and G. Scandariato and D. Ségransan and D. Sicilia and A. E. Simon and A. M. S. Smith and M. Steller and Gy. M. Szabó and N. Thomas and S. Udry and B. Ulmer and V. Van Grootel and J. Venturini and N. A. Walton and T. G. Wilson and D. Wolter},
journal= {arXiv preprint arXiv:2307.06085},
year = {2023}
}
Comments
27 pages, 22 figures. Accepted for publication on A&A