Discovery and Characterization of the TOI-4468 Planetary System: A Transiting Hot Jupiter with a Lone Nearby Outer Companion

@article{livesey2026discovery,
  title = {{Discovery and Characterization of the TOI-4468 Planetary System: A Transiting Hot Jupiter with a Lone Nearby Outer Companion}},
  author = {Joseph R. Livesey and Benjamin J. Hord and Juliette Becker and Andrew Vanderburg and Joseph E. Rodriguez and Elise Koo and Chelsea X. Huang and Guðmundur Stefánsson and Karen A. Collins and Ivan A. Strakhov and Zijun He and Maxwell A. Kroft and Robert Aloisi and Khalid Barkaoui and Fabian Rodriguez Frustaglia and Alyssa Jankowski and Kinga Kasprzyk and Judith Korth and Coleman Nelson and Hannu Parviainen and Adam Popowicz and Manfred Raetz and Richard P. Schwarz and Eva Stafne and Keivan G. Stassun and Thomas G. Beatty and Paul Foster and Thomas MacLean and Devansh Mathur and Lizhou Sha and Melinda Soares-Furtado},
  journal = {The Astronomical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-3881/aeaee4},
  url = {https://iopscience.iop.org/article/10.3847/1538-3881/aeaee4},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Discovery and Characterization of the TOI-4468 Planetary System: A Transiting Hot Jupiter with a Lone Nearby Outer Companion
AU  - Joseph R. Livesey
AU  - Benjamin J. Hord
AU  - Juliette Becker
AU  - Andrew Vanderburg
AU  - Joseph E. Rodriguez
AU  - Elise Koo
AU  - Chelsea X. Huang
AU  - Guðmundur Stefánsson
AU  - Karen A. Collins
AU  - Ivan A. Strakhov
AU  - Zijun He
AU  - Maxwell A. Kroft
AU  - Robert Aloisi
AU  - Khalid Barkaoui
AU  - Fabian Rodriguez Frustaglia
AU  - Alyssa Jankowski
AU  - Kinga Kasprzyk
AU  - Judith Korth
AU  - Coleman Nelson
AU  - Hannu Parviainen
AU  - Adam Popowicz
AU  - Manfred Raetz
AU  - Richard P. Schwarz
AU  - Eva Stafne
AU  - Keivan G. Stassun
AU  - Thomas G. Beatty
AU  - Paul Foster
AU  - Thomas MacLean
AU  - Devansh Mathur
AU  - Lizhou Sha
AU  - Melinda Soares-Furtado
PY  - 2026
DA  - 2026/10/29
JO  - The Astronomical Journal
DO  - 10.3847/1538-3881/aeaee4
UR  - https://iopscience.iop.org/article/10.3847/1538-3881/aeaee4
AB  - We report the discovery of two planets, a hot Jupiter (HJ) and a nearby outer sub-Neptune, orbiting the star TOI-4468. This system is unique among the current exoplanet census in that it features a close outer companion to a HJ without an accompanying inner companion. By jointly fitting radial velocity (RV) measurements taken with the NEID spectrograph and transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and several ground-based observatories, we constrain the orbital periods, masses, and radii of these two planets. We confirm the planetary nature of the HJ TOI-4468 b ( R = 1.01 R J , m = 0.54 M J , P = 2.77 days). We also validate the outer planet TOI-4468 c ( R = 0.28 R J , P = 7.01 days) statistically, incorporating constraints from ground-based observations. We also identify, but cannot confirm, an additional RV signal that may be due to an outer giant in this system with an orbital period of 624 days. From the observed geometry of this system, we argue that it must never have encountered an early secular resonance that is thought to excite the mutual inclination of other HJ/outer companion systems. We discuss the possibility of an undetected inner companion, as well as potential implications for HJ formation.
SN  - 0004-6256
SN  - 1538-3881
ER  -