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Transit timing variations of AU Microscopii b and c

Gy. M. Szabó, Z. Garai, A. Brandeker, D. Gandolfi, T. G. Wilson, A. Deline, G. Olofsson, A. Fortier, D. Queloz, L. Borsato, F. Kiefer, A. Lecavelier Des Etangs, M. Lendl, L. M. Serrano, S. Sulis, S. Ulmer-Moll, V. Van Grootel, Y. Alibert, R. Alonso, G. Anglada-Escudé, T. Bárczy, D. Barrado y Navascues, S. C. C. Barros, W. Baumjohann, M. Beck, T. Beck, W. Benz, N. Billot, A. Bonfanti, X. Bonfils, C. Broeg, J. Cabrera, S. Charnoz, A. Collier Cameron, Sz. Csizmadia, M. B. Davies, M. Deleuil, L. Delrez, O. Demangeon, B.-O. Demory, D. Ehrenreich, A. Erikson, L. Fossati, M. Fridlund, M. Gillon, M. Güdel, K. Heng, S. Hoyer, K. Isaak, L. L. Kiss, J. Laskar, C. Lovis, D. Magrin, P. F. L. Maxted, M. Mecina, V. Nascimbeni, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, M. Sarajlic, G. Scandariato, D. Ségransan, A. E. Simon, A. M. S. Smith, S. G. Sousa, M. Steller, N. Thomas, S. Udry, F. Verrecchia, N. A. Walton, D. Wolter

Abstract
Here we report large-amplitude transit timing variations (TTVs) for AU Microcopii b and c as detected in combined TESS (2018, 2020) and CHEOPS (2020, 2021) transit observations. AU Mic is a young planetary system with a debris disk and two transiting warm Neptunes. A TTV on the order of several minutes was previously reported for AU Mic b, which was suggested to be an outcome of mutual perturbations between the planets in the system. In 2021, we observed AU Mic b (five transits) and c (three transits) with the CHEOPS space telescope to follow-up the TTV of AU Mic b and possibly detect a TTV for AU Mic c. When analyzing TESS and CHEOPS 2020−2021 measurements together, we find that a prominent TTV emerges with a full span of ≥23 min between the two TTV extrema. Assuming that the period change results from a periodic process –such as mutual perturbations– we demonstrate that the times of transits in the summer of 2022 are expected to be 30−85 min later than predicted by the available linear ephemeris.

Keywords
planets and satellites: fundamental parameters / planets and satellites: individual: AU Mic b and c

Notes
The CHEOPS data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/659/L7

Astronomy & Astrophysics
Volume 659, Article Number L7, Number of pages 9
2022 March

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia