CHEOPS photometry from 2024 reveals a reversal in the transit-timing variations of AU Mic c

arXiv:2608.01120 · astro-ph.EP · Submitted 2026-08-02 · Read on arXiv

Z. Garai, Gy. M. Szabó, D. Gandolfi, A. Brandeker, A. Bonfanti, N. Billot, W. Benz, A. Heitzmann, G. Olofsson, L. Kriskovics, Á. Boldog, L. Borsato, A. Bekkelien, G. Bruno, H. P. Osborn, S. Ulmer-Moll, T. G. Wilson, Y. Alibert, R. Alonso, T. Bárczy, D. Barrado, S. C. C. Barros, W. Baumjohann, C. Broeg, A. Castro-González, A. Collier Cameron, A. C. M. Correia, Sz. Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, A. Deline, O. D. S. Demangeon, B. -O. Demory, A. Derekas, B. Edwards, D. Ehrenreich, A. Erikson, A. Fortier, L. Fossati, M. Fridlund, K. Gazeas, M. Gillon, M. Güdel, M. N. Günther, Ch. Helling, K. G. Isaak, T. Keller, L. L. Kiss, D. Kitzmann, J. Korth, K. W. F. Lam, J. Laskar, A. Lecavelier des Etangs, A. Leleu, M. Lendl, D. Magrin, P. F. L. Maxted, B. Merín, C. Mordasini, V. Nascimbeni, D. Orikhovskyi, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, D. Piazza, G. Piotto, D. Pollacco, T. Pribulla, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, M. Rieder, N. C. Santos, G. Scandariato, D. Ségransan, A. E. Simon, A. M. S. Smith, S. G. Sousa, R. Southworth, M. Stalport, M. Steinberger, S. Sulis, S. Udry, B. Ulmer, V. Van Grootel, J. Venturini, E. Villaver, V. Viotto, N. A. Walton

astro-ph.EP

Submitted: 2026-08-02

Comments: Accepted for publication in A&A

Code: https://github.com/pavolgaj/OCFit

License: http://creativecommons.org/licenses/by/4.0/

The gist: We present new CHEOPS transit observations of AU Mic b and AU Mic c obtained between June and September 2024, extending the baseline of transit-timing measurements of this young planetary system.

Terminology

Active Regions — 2× in this paper · explained in 1 episode
European Space Agency — 2× in this paper
Aperture — 1× in this paper · explained in 1 episode
European Space Astronomy Centre — 1× in this paper
GO and Guaranteed Time Observation — 1× in this paper
Guest Observers — 1× in this paper
Metallicity — 1× in this paper · explained in 3 episodes
Robustness — 1× in this paper · explained in 5 episodes

Abstract

We present new CHEOPS transit observations of AU Mic b and AU Mic c obtained between June and September 2024, extending the baseline of transit-timing measurements of this young planetary system. For AU Mic b, the timing signal is well established, with a semi-amplitude (10 plus or minus 3 min) and a characteristic modulation timescale (1168 plus or minus 20 d) consistent with previous determinations. By contrast, the new CHEOPS data show that the large transit-timing deviation of AU Mic c reported previously was not sustained. After the steadily increasing timing trend observed in 2022 and 2023, the 2024 timings returned closer to the zero point of the observed-minus-calculated diagram, indicating a reversal of the previously reported behavior. For AU Mic c, both the transit-timing semi-amplitude (46 plus or minus 26 min) and the characteristic modulation timescale (2150 plus or minus 110 d) remain tentative. These results highlight the importance of continued long-term monitoring of the AU Mic system.

Terminology

Abstract

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