HIP 41378 observed by CHEOPS: Where is planet d?
Alonso, R.; Deleuil, M.; Erikson, A.; Fridlund, M.; Queloz, D.; Rauer, H.; Olofsson, G.; Pallé, E.; Ribas, I.; Güdel, M.; Isaak, K. G.; Scandariato, G.; Pagano, I.; Baumjohann, W.; Derekas, A.; Gandolfi, D.; Fossati, L.; Korth, J.; Csizmadia, Sz.; Smith, A. M. S.; Ségransan, D.; Walton, N. A.; Ragazzoni, R.; Piotto, G.; Benz, W.; Deline, A.; Collier Cameron, A.; Alibert, Y.; Delrez, L.; Fortier, A.; Hoyer, S.; Bonfanti, A.; Sousa, S. G.; Wilson, T. G.; Bárczy, T.; Barros, S. C. C.; Beck, T.; Billot, N.; Borsato, L.; Brandeker, A.; Broeg, C.; Davies, M. B.; Demangeon, O. D. S.; Demory, B. -O.; Ehrenreich, D.; Gillon, M.; Kiss, L. L.; Lam, K. W. F.; Laskar, J.; Lecavelier des Etangs, A.; Lendl, M.; Magrin, D.; Maxted, P. F. L.; Nascimbeni, V.; Osborn, H. P.; Ottensamer, R.; Peter, G.; Pollacco, D.; Rando, N.; Santos, N. C.; Simon, A. E.; Szabó, Gy. M.; Udry, S.; Van Grootel, V.; Helling, Ch.; Gazeas, K.; Steinberger, M.; Sulis, S.; Bergomi, M.; Santerne, A.; Cubillos, P. E.; Correia, A. C. M.; Barrado Navascues, D.; Günther, M. N.; Heitzmann, A.; Mordasini, C.; Piazza, D.; Stalport, M.; Venturini, J.; Villaver, E.; Grouffal, S.; Ulmer-Moll, S.; Zingales, T.; Edwards, B.; Wolter, D.; Tuson, A.; Corral van Damme, C.
France, Italy, Switzerland, United States, Sweden, Netherlands, Spain, Hungary, Portugal, Austria, United Kingdom, Germany, Belgium, Greece
Abstract
HIP 41378 d is a long-period planet that has only been observed to transit twice, three years apart, with K2. According to stability considerations and a partial detection of the Rossiter-McLaughlin effect, Pd = 278.36 d has been determined to be the most likely orbital period. We targeted HIP 41378 d with CHEOPS at the predicted transit timing based on Pd = 278.36 d, but the observations show no transit. We find that large (> 22.4 h) transit timing variations (TTVs) could explain this non-detection during the CHEOPS observation window. We also investigated the possibility of an incorrect orbital solution, which would have major implications for our knowledge of this system. If Pd ≠ 278.36 d, the periods that minimize the eccentricity would be 101.22 d and 371.14 d. The shortest orbital period will be tested by TESS, which will observe HIP 41378 in Sector 88 starting in January 2025. Our study shows the importance of a mission like CHEOPS, which today is the only mission able to make long observations (i.e., from space) to track the ephemeris of long-period planets possibly affected by large TTVs.
The raw and detrended photometric time-series data are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/686/L18 The CHEOPS program ID is CH_PR110048.