Tidally Heated Sub-Neptunes, Refined Planetary Compositions, and Confirmation of a Third Planet in the TOI-1266 System

TOI-1266 is a benchmark system of two temperate (< 450 K) sub-Neptune-sized planets orbiting a nearby M dwarf exhibiting a rare inverted architecture with a larger interior planet.

In this study, we characterize transit timing variations (TTVs) in the TOI-1266 system using high-precision ground-based follow-up and new TESS data. We confirm the presence of a third exterior non-transiting planet, TOI-1266 d (P = 32.5 d, Md = 3.68+1.05−1.11M_⊕), and combine the TTVs with archival radial velocity (RV) measurements to improve our knowledge of the planetary masses and radii.

We find that, consistent with previous studies, TOI-1266 b (Rb = 2.52 ± 0.08 R_⊕, Mb = 4.46 ± 0.69 M_⊕) has a low bulk density requiring the presence of a hydrogen-rich envelope, while TOI-1266 c (Rc = 1.98 ± 0.10 R⊕, Mc = 3.17 ± 0.76 M_⊕) has a higher bulk density that can be matched by either a hydrogen-rich or water-rich envelope. Our new dynamical model reveals that this system is arranged in a rare configuration with the inner and outer planets located near the 3:1 period ratio with a non-resonant planet in between them.

Our dynamical fits indicate that the inner and outer planet have significantly nonzero eccentricities (eb+ed=0.076+0.029−0.019), suggesting that TOI-1266 b may have an inflated envelope due to tidal heating. F

inally, we explore the corresponding implications for the formation and long-term evolution of the system, which contains two of the most favorable cool (< 500 K) sub-Neptunes for atmospheric characterization with JWST.

Michael Greklek-McKeon, Shreyas Vissapragada, Heather A. Knutson, Akihiko Fukui, Morgan Saidel, Jonathan Gomez Barrientos, W. Garrett Levine, Aida Behmard, Konstantin Batygin, Yayaati Chachan, Gautam Vasisht, Renyu Hu, Ryan Cloutier, David Latham, Mercedes López-Morales, Andrew Vanderburg, Carolyn Heffner, Paul Nied, Jennifer Milburn, Isaac Wilson, Diana Roderick, Kathleen Koviak, Tom Barlow, John F. Stone, Rocio Kiman, Judith Korth, Jerome P. de Leon, Izuru Fukuda, Yuya Hayashi, Masahiro Ikoma, Kai Ikuta, Keisuke Isogai, Yugo Kawai, Kiyoe Kawauchi, Nobuhiko Kusakabe, John H. Livingston, Mayuko Mori, Norio Narita, Motohide Tamura, Noriharu Watanabe, Gareb Fernández-Rodríguez

Comments: 36 pages, 19 figures, 5 tables, submitted to The Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2409.16374 [astro-ph.EP] (or arXiv:2409.16374v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2409.16374
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Submission history
From: Michael Greklek-McKeon
[v1] Tue, 24 Sep 2024 18:08:01 UTC (16,877 KB)
https://arxiv.org/abs/2409.16374
Astrobiology, Astrogeology,