TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K Dwarf

Creators: Mireles, Ismael¹; Dragomir, Diana¹; Osborn, Hugh P.^{2, 3}; Hesse, Katharine³; Collins, Karen A.⁴; Villanueva, Steven⁵; Bieryla, Allyson⁴; Ciardi, David R.^{6, 7}; Stassun, Keivan G.⁸; Harris, Mallory¹; Lissauer, Jack J.⁹; Schwarz, Richard P.⁴; Srdoc, Gregor¹⁰; Barkaoui, Khalid^{11, 3, 12}; Riffeser, Arno¹³; McLeod, Kim K.¹⁴; Pepper, Joshua¹⁵; Grieves, Nolan¹⁶; Passegger, Vera Maria^{12, 17, 18, 19}; Ulmer-Moll, Solène¹⁶; Rodriguez, Joseph E.²⁰; Feliz, Dax L.²¹; Quinn, Samuel⁴; Boyle, Andrew W.^{6, 7}; Fausnaugh, Michael³; Kunimoto, Michelle³; Rowden, Pamela²²; Vanderburg, Andrew³; Wohler, Bill^{9, 23}; Jenkins, Jon M.⁹; Latham, David W.⁴; Ricker, George R.³; Seager, Sara³; Winn, Joshua N.²⁴

1. University of New Mexico
2. University of Bern
3. Massachusetts Institute of Technology
4. Harvard-Smithsonian Center for Astrophysics
5. Goddard Space Flight Center
6. NASA Exoplanet Science Institute
7. California Institute of Technology
8. Vanderbilt University
9. Ames Research Center
10. Kotizarovci Observatory, Sarsoni 90, 51216 Viskovo, Croatia
11. University of Liège
12. Instituto de Astrofísica de Canarias
13. Ludwig-Maximilians-Universität München
14. Wellesley College
15. Lehigh University
16. University of Geneva
17. University of La Laguna
18. Universität Hamburg
19. University of Oklahoma
20. Michigan State University
21. American Museum of Natural History
22. Royal Astronomical Society
23. Search for Extraterrestrial Intelligence
24. Princeton University

Abstract

We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600 (V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of 6.80 ± 0.31 R ⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R ⊕ and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm Jupiters and the solar system's gas giants. TOI-4600 is a promising target for further transit and precise RV observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets. Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems with multiple giant exoplanets.

Copyright and License

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

We thank the anonymous reviewer for their helpful comments, which have helped improve the paper. Funding for the TESS mission is provided by NASA's Science Mission Directorate. We also thank Steven Giacalone for his assitance with configuring triceratops. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work makes use of observations from the LCOGT network. D.D. acknowledges support from the TESS Guest Investigator Program grants 80NSSC21K0108 and 80NSSC22K0185, and NASA Exoplanet Research Program grant 18-2XRP18_2-0136. H.P.O.'s and S.U.'s contributions have been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. The postdoctoral fellowship of K.B. is funded by F.R.S. (FNRS grant T.0109.20) and by the Francqui Foundation. K.K.M. acknowledges support from the New York Community Trust Fund for Astrophysical Research. This work made use of exoplanet (Foreman-Mackey et al. 2021a, 2021b) and its dependencies (Astropy Collaboration et al. 2013, 2018; Salvatier et al. 2016; Theano Development Team 2016; Kumar et al. 2019; Luger et al. 2019; Van Eylen et al. 2019; Agol et al. 2020).

Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific data sets used in this work come from the TESS all section calibrated FFIs (STScI 2022), the TESS All sector light curves (MAST Team 2021a), and the TESS all sectors target pixel files ( MAST Team 2021b).

Facilities

TESS - , LCOGT - Las Cumbres Observatory Global Telescope, and Exoplanet Archive - .

Software References

AstroImageJ (Collins et al. 2017), astropy (Astropy Collaboration et al. 2013, 2018), and TAPIR (Jensen 2013).

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