Tidally Heated Sub-Neptunes, Refined Planetary Compositions, and Confirmation of a Third Planet in the TOI-1266 System
(2025) In Astronomical Journal 169(6).- Abstract
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 nontransiting planet, TOI-1266 d (P = 32.5 days, Md = 3.68 − 1.11 + 1.05 M ⊕ ), and combine the TTVs with archival radial velocity 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... (More)
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 nontransiting planet, TOI-1266 d (P = 32.5 days, Md = 3.68 − 1.11 + 1.05 M ⊕ ), and combine the TTVs with archival radial velocity 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 nonresonant planet in between them. Our dynamical fits indicate that the inner and outer planet have significantly nonzero eccentricities ( e b + e d = 0.07 6 − 0.019 + 0.029 ), suggesting that TOI-1266 b may have an inflated envelope due to tidal heating. Finally, 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.
(Less)
- author
- organization
- publishing date
- 2025-06
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Astronomical Journal
- volume
- 169
- issue
- 6
- article number
- 292
- publisher
- IOP Publishing
- external identifiers
-
- scopus:105004647467
- ISSN
- 0004-6256
- DOI
- 10.3847/1538-3881/adc0fe
- language
- English
- LU publication?
- yes
- id
- 2d213303-6bde-4387-88e4-5e7a5b2e771e
- date added to LUP
- 2025-07-30 13:05:14
- date last changed
- 2025-07-30 13:05:31
@article{2d213303-6bde-4387-88e4-5e7a5b2e771e,
abstract = {{<p>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 nontransiting planet, TOI-1266 d (P = 32.5 days, M<sub>d</sub> = 3.68 − 1.11 + 1.05 M ⊕ ), and combine the TTVs with archival radial velocity measurements to improve our knowledge of the planetary masses and radii. We find that, consistent with previous studies, TOI-1266 b (R<sub>b</sub> = 2.52 ± 0.08 R<sub>⊕</sub>, M<sub>b</sub> = 4.46 ± 0.69 M<sub>⊕</sub>) has a low bulk density requiring the presence of a hydrogen-rich envelope, while TOI-1266 c (R<sub>c</sub> = 1.98 ± 0.10 R<sub>⊕</sub>, M<sub>c</sub> = 3.17 ± 0.76 M<sub>⊕</sub>) 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 nonresonant planet in between them. Our dynamical fits indicate that the inner and outer planet have significantly nonzero eccentricities ( e b + e d = 0.07 6 − 0.019 + 0.029 ), suggesting that TOI-1266 b may have an inflated envelope due to tidal heating. Finally, 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.</p>}},
author = {{Greklek-McKeon, Michael and Vissapragada, Shreyas and Knutson, Heather A. and Fukui, Akihiko and Saidel, Morgan and Gomez Barrientos, Jonathan and Levine, W. Garrett and Behmard, Aida and Batygin, Konstantin and Chachan, Yayaati and Vasisht, Gautam and Hu, Renyu and Cloutier, Ryan and Latham, David and López-Morales, Mercedes and Vanderburg, Andrew and Heffner, Carolyn and Nied, Paul and Milburn, Jennifer and Wilson, Isaac and Roderick, Diana and Koviak, Kathleen and Barlow, Tom and Stone, John F. and Kiman, Rocio and Korth, Judith and de Leon, Jerome P. and Fukuda, Izuru and Hayashi, Yuya and Ikoma, Masahiro and Ikuta, Kai and Isogai, Keisuke and Kawai, Yugo and Kawauchi, Kiyoe and Kusakabe, Nobuhiko and Livingston, John H. and Mori, Mayuko and Narita, Norio and Tamura, Motohide and Watanabe, Noriharu and Fernández-Rodríguez, Gareb}},
issn = {{0004-6256}},
language = {{eng}},
number = {{6}},
publisher = {{IOP Publishing}},
series = {{Astronomical Journal}},
title = {{Tidally Heated Sub-Neptunes, Refined Planetary Compositions, and Confirmation of a Third Planet in the TOI-1266 System}},
url = {{http://dx.doi.org/10.3847/1538-3881/adc0fe}},
doi = {{10.3847/1538-3881/adc0fe}},
volume = {{169}},
year = {{2025}},
}