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arXiv · 2610.28533

TOI-3686: A Hot Jupiter and Sub-Neptune In A 2:1 Mean-Motion Resonance

Samuel W. Yee·Tarisai Dziire·Karen A. Collins·Luke G. Bouma·Daniel Tamayo·Erik A. Petigura·Allyson Bieryla·David W. Latham·Samuel N. Quinn·Joshua N. Winn·Joel D. Hartman·Boris S. Safonov·Raquel Forés-Toribio·Jose A. Muñoz·Khalid Barkaoui·Richard P. Schwarz·Francis P. Wilkin·Paul Benni·Krzysztof Bernacki·Nikita Chazov·Eric G. Hintz·Glauk Hizmo·George Iwaszek·Adam Popowicz·Manfred Raetz·Miquel Serra-Ricart·Gregor Srdoc·Denise C. Stephens·Joseph Williams·Valerio Bozza·Otabek Burkhonov·Roger Dymock·Salokhiddin Sh. Ergashev·Karen Fischer·Cristilyn N. Gardner-Watkins·Ferran Grau Horta·Adam Lark·Katherine Linnenkohl·Ken Mason·Edward J. Michaels·Owen A. J. Mitchem·Seth M. Pritchard·Lauren A. Sgro·Neil B. Thomas·Siegfried Vanaverbeke·Pieter Vuylsteke·Jeroen Audenaert·Keith Horne·Felipe Murgas·Emma Nabbie·Enric Palle·Ramotholo Sefako·Avi Shporer
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Abstract

Hot Jupiters are typically thought to be "lonely", but a small and growing subset of them have been found to have nearby planets in the same system. We present the discovery of a new member of this class of systems, TOI-3686. TOI-3686 c is a hot Jupiter with $P_\mathrm{orb} = 5.078$ days detected by NASA's TESS mission that shows peak-to-peak transit timing variations (TTVs) of 40 minutes, amongst the largest ever observed for a hot Jupiter. A subsequent search of the TESS data revealed the transits of a second planet, TOI-3686 b, a sub-Neptune with $P_\mathrm{orb} = 2.54$~days and peak-to-peak TTVs of 10 hours, $\sim 16\%$ of its orbital period. We characterized the system through photodynamical modeling of photometry from TESS and ground-based facilities, as well as radial velocity measurements from the NEID and MAROON-X spectrographs. We find that the two planets in the TOI-3686 system are deep in a 2:1 mean-motion resonance, making this the only hot Jupiter system currently known to be in a truly resonant configuration, which may be related to its $\lesssim1$~Gyr system age. Systems like TOI-3686 likely formed through a dynamically quiescent pathway and were captured into resonance after migration through a disk, and may represent the high-mass end of processes that occur in compact systems of smaller planets.

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Samuel W. Yee, Tarisai Dziire, Karen A. Collins, Luke G. Bouma, Daniel Tamayo, Erik A. Petigura, Allyson Bieryla, David W. Latham, Samuel N. Quinn, Joshua N. Winn, Joel D. Hartman, Boris S. Safonov, Raquel Forés-Toribio, Jose A. Muñoz, Khalid Barkaoui, Richard P. Schwarz, Francis P. Wilkin, Paul Benni, Krzysztof Bernacki, Nikita Chazov, Eric G. Hintz, Glauk Hizmo, George Iwaszek, Adam Popowicz, Manfred Raetz, Miquel Serra-Ricart, Gregor Srdoc, Denise C. Stephens, Joseph Williams, Valerio Bozza, Otabek Burkhonov, Roger Dymock, Salokhiddin Sh. Ergashev, Karen Fischer, Cristilyn N. Gardner-Watkins, Ferran Grau Horta, Adam Lark, Katherine Linnenkohl, Ken Mason, Edward J. Michaels, Owen A. J. Mitchem, Seth M. Pritchard, Lauren A. Sgro, Neil B. Thomas, Siegfried Vanaverbeke, Pieter Vuylsteke, Jeroen Audenaert, Keith Horne, Felipe Murgas, Emma Nabbie, Enric Palle, Ramotholo Sefako, Avi Shporer. 2026-10-20. TOI-3686: A Hot Jupiter and Sub-Neptune In A 2:1 Mean-Motion Resonance. https://arxiv.org/abs/2610.28533

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