arXiv · 2203.03194
Uncovering the true periods of the young sub-Neptunes orbiting TOI-2076
Abstract
Context: TOI-2076 is a transiting three-planet system of sub-Neptunes orbiting a bright (G = 8.9 mag), young ($340\pm80$ Myr) K-type star. Although a validated planetary system, the orbits of the two outer planets were unconstrained as only two non-consecutive transits were seen in TESS photometry. This left 11 and 7 possible period aliases for each. Aims: To reveal the true orbits of these two long-period planets, precise photometry targeted on the highest-probability period aliases is required. Long-term monitoring of transits in multi-planet systems can also help constrain planetary masses through TTV measurements. Methods: We used the MonoTools package to determine which aliases to follow, and then performed space-based and ground-based photometric follow-up of TOI-2076 c and d with CHEOPS, SAINT-EX, and LCO telescopes. Results: CHEOPS observations revealed a clear detection for TOI-2076 c at $P=21.01538^{+0.00084}_{-0.00074}$ d, and allowed us to rule out three of the most likely period aliases for TOI-2076 d. Ground-based photometry further enabled us to rule out remaining aliases and confirm the $P=35.12537\pm0.00067$ d alias. These observations also improved the radius precision of all three sub-Neptunes to $2.518\pm0.036$, $3.497\pm0.043$, and $3.232\pm0.063$ $R_\oplus$. Our observations also revealed a clear anti-correlated TTV signal between planets b and c likely caused by their proximity to the 2:1 resonance, while planets c and d appear close to a 5:3 period commensurability, although model degeneracy meant we were unable to retrieve robust TTV masses. Their inflated radii, likely due to extended H-He atmospheres, combined with low insolation makes all three planets excellent candidates for future comparative transmission spectroscopy with JWST.
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Hugh P. Osborn, Andrea Bonfanti, Davide Gandolfi, Christina Hedges, Adrien Leleu, Andrea Fortier, David Futyan, Pascal Gutermann, Pierre F. L. Maxted, Luca Borsato, Karen A. Collins, J. Gomes da Silva, Yilen Gómez Maqueo Chew, Matthew J. Hooton, Monika Lendl, Hannu Parviainen, Sébastien Salmon, Nicole Schanche, Luisa M. Serrano, Sergio G. Sousa, Amy Tuson, Solène Ulmer-Moll, Valerie Van Grootel, R. D. Wells, Thomas G. Wilson, Yann Alibert, Roi Alonso, Guillem Anglada, Joel Asquier, David Barrado y Navascues, Wolfgang Baumjohann, Thomas Beck, Willy Benz, Federico Biondi, Xavier Bonfils, Francois Bouchy, Alexis Brandeker, Christopher Broeg, Tamas Bárczy, S. C. C. Barros, Juan Cabrera, Sébastien Charnoz, Andrew Collier Cameron, Szilard Csizmadia, Melvyn B. Davies, Magali Deleuil, Laetitia Delrez, Brice-Olivier Demory, David Ehrenreich, Anders Erikson, Luca Fossati, Malcolm Fridlund, Michaël Gillon, M. A. Gómez-Muñoz, Manuel Güdel, Kevin Heng, Sergio Hoyer, Kate G. Isaak, Laszlo Kiss, Jacques Laskar, Alain Lecavelier des Etangs, Christophe Lovis, Demetrio Magrin, Luca Malavolta, James McCormac, Valerio Nascimbeni, Göran Olofsson, Roland Ottensamer, Isabella Pagano, Enric Pallé, Gisbert Peter, Daniele Piazza, Giampaolo Piotto, Don Pollacco, Didier Queloz, Roberto Ragazzoni, Nicola Rando, Heike Rauer, Christian Reimers, Ignasi Ribas, Olivier D. S. Demangeon, Alexis M. S. Smith, L. Sabin, Nuno Santos, Gaetano Scandariato, U. Schroffenegger, Rick P. Schwarz, Avi Shporer, Attila E. Simon, Manfred Steller, Gyula M. Szabó, Damien Ségransan, Nicolas Thomas, Stéphane Udry, Ingo Walter, Nicholas Walton. 2022-03-07. Uncovering the true periods of the young sub-Neptunes orbiting TOI-2076. https://doi.org/10.1051/0004-6361/202243065
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