Transit-timing variations in the AU Mic system observed with CHEOPS
Abstract
AU Mic is a very active M dwarf with an edge-on debris disk and two transiting sub-Neptunes with a possible third planetary companion. The two transiting planets exhibit significant transit-timing variations (TTVs) that are caused by the gravitational interaction between the bodies in the system. Using photometrical observations taken with the CHaracterizing ExOPlanet Satellite (CHEOPS), our goal is to constrain the planetary radii, the orbital distances and periods of AU Mic b and c. We aim to determine the superperiod of the TTVs for AU Mic b and to update the transit ephemeris for both planets. Based on the observed TTVs, we study the possible presence of a third planet in the system. We conducted high precision photometric observations with CHEOPS in 2022 and 2023. We used Allesfitter to fit the planetary transits and to constrain the planetary and orbital parameters. We combined our new measurements with results from previous years to determine the periods and amplitudes of the TTVs. We applied dynamical modelling based on TTV measurements from the 2018-2023 period to reconstruct the perceived variations. The orbital distances and periods for AU Mic b and c agree with the results from previous works. However, the values for the planetary radii deviate slightly from previous values, which we attribute to the effect of stellar spots. AU Mic c showed very strong TTVs, with transits that occurred ~80 minutes later in 2023 than in 2021. Through dynamical analysis of the system, we found that the observed TTVs can be explained by a third planet with an orbital period of ~12.6 days and a mass of 0.203+0.022-0.024 M_E. We explored the orbital geometry of the system and found that AU Mic c has a misaligned retrograde orbit. Due limited number of observations the exact configuration and planetary parameters could not be determined. Further monitoring with CHEOPS may improve these results.
Cite
@article{arxiv.2501.13575,
title = {Transit-timing variations in the AU Mic system observed with CHEOPS},
author = {Á. Boldog and Gy. M. Szabó and L. Kriskovics and L. Borsato and D. Gandolfi and M. Lendl and M. N. Günther and A. Heitzmann and T. G. Wilson and A. Brandeker and Z. Garai and Y. Alibert and R. Alonso and T. Bárczy and D. Barrado Navascues and S. C. C. Barros and W. Baumjohann and W. Benz and N. Billot and C. Broeg and A. Collier Cameron and A. C. M. Correia and Sz. Csizmadia and P. E. Cubillos and M. B. Davies and M. Deleuil and A. Deline and O. D. S. Demangeon and B. -O. Demory and A. Derekas and B. Edwards and J. A. Egger and D. Ehrenreich and A. Erikson and A. Fortier and L. Fossati and M. Fridlund and K. Gazeas and M. Gillon and M. Güdel and P. Guterman and Ch. Helling and K. G. Isaak and L. L. Kiss and E. Kopp and J. Korth and K. W. F. Lam and J. Laskar and A. Lecavelier des Etangs and A. Luntzer and D. Magrin and G. Mantovan and L. Marafatto and P. F. L. Maxted and B. Merín and C. Mordasini and M. Munari and V. Nascimbeni and G. Olofsson and R. Ottensamer and I. Pagano and E. Pallé and G. Peter and D. Piazza and G. Piotto and D. Pollacco and K. Poppenhaeger and D. Queloz and R. Ragazzoni and N. Rando and H. Rauer and I. Ribas and M. Rieder and N. C. Santos and G. Scandariato and D. Ségransan and A. E. Simon and A. M. S. Smith and S. G. Sousa and R. Southworth and M. Stalport and S. Sulis and S. Udry and S. Ulmer-Moll and V. Van Grootel and J. Venturini and E. Villaver and N. A. Walton and T. Zingales},
journal= {arXiv preprint arXiv:2501.13575},
year = {2025}
}
Comments
15 pages, 10 figures