CaltechAUTHORS
Published July 2025 | Version Published
Journal Article Open

Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. VI. Confirmation of a Long-period Giant Planet Discovered with a Single TESS Transit

Creators

  • 1. ROR icon University of New Mexico
  • 2. ROR icon University of California, Santa Cruz
  • 3. ROR icon University of Geneva
  • 4. ROR icon NASA Exoplanet Science Institute
  • 5. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 6. ROR icon Ames Research Center
  • 7. ROR icon European Southern Observatory
  • 8. ROR icon University of California, Riverside
  • 9. ROR icon Jet Propulsion Lab
  • 10. ROR icon National Research Council Canada
  • 11. ROR icon Search for Extraterrestrial Intelligence
  • 12. ROR icon Vanderbilt University
  • 13. ROR icon University of Bern
  • 14. ROR icon Stephen F. Austin State University
  • 15. ROR icon University of Warwick
  • 16. ROR icon University of Liège
  • 17. ROR icon Massachusetts Institute of Technology
  • 18. ROR icon Instituto de Astrofísica de Canarias
  • 19. ROR icon Adolfo Ibáñez University
  • 20. ROR icon Millennium Institute of Astrophysics
  • 21. Data Observatory Foundation, Chile
  • 22. ROR icon University College London
  • 23. Unistellar, 5 allée Marcel Leclerc, bâtiment B, Marseille, 13008, France
  • 24. ROR icon University of California, Berkeley
  • 25. ROR icon California Institute of Technology
  • 26. ROR icon University of Southern Queensland
  • 27. ROR icon University of Leicester
  • 28. ROR icon University of North Carolina at Chapel Hill
  • 29. ROR icon United States Naval Observatory
  • 30. ROR icon University of La Laguna
  • 31. ROR icon Diego Portales University
  • 32. ROR icon South African Radio Astronomy Observatory
  • 33. ROR icon Lomonosov Moscow State University
  • 34. ROR icon Goddard Space Flight Center
  • 35. ROR icon Princeton University
  • 36. Observatori Astronòmic Albanyà, Camí de Bassegoda S/N, Albanyá 17733, Girona, Spain
  • 37. ROR icon University of Lethbridge
  • 38. ROR icon George Mason University
  • 39. ROR icon University of Valencia
  • 40. ROR icon American Association of Variable Star Observers
  • 41. Frustaglia Private Observatory, Spain
  • 42. Grand-Pra Observatory, 1984 Les Hauderes, Switzerland
  • 43. The Maury Lewin Astronomical Observatory, Glendora, CA 91741, USA
  • 44. Kotizarovci Observatory, Sarsoni 90, 51216 Viskovo, Croatia
  • 45. Hazelwood Observatory, Australia
  • 46. Laboratoire d'Astrophysique des Baronnies, Science Citoyenne et Actions pour la Nuit (LABSCAN), Moydans, France
  • 47. Unistellar Citizen Scientist, Vienna, Austria
  • 48. Unistellar Citizen Scientist, Maxéville, France
  • 49. Unistellar Citizen Scientist, Temecula, CA, USA
  • 50. Unistellar Citizen Scientist, Tsuchiura, Ibaraki, Japan
  • 51. Unistellar Citizen Scientist, Puy-Saint-Vincent, France
  • 52. Unistellar Citizen Scientist, Ames, IA, USA
  • 53. Unistellar Citizen Scientist, Tonbridge, Kent, UK
  • 54. Unistellar Citizen Scientist, Archenhold Observatory, Finowfurt, Brandenburg, Germany
  • 55. Unistellar Citizen Scientist, Valeggio sul Mincio, Verona, Italy
  • 56. Unistellar Citizen Scientist, Bayonne, France
  • 57. Unistellar Citizen Scientist, Tonosyo, Kagawa, Japan
  • 58. Unistellar Citizen Scientist, Renens, Vaud, Switzerland
  • 59. Unistellar Citizen Scientist, Lattes, France
  • 60. Unistellar Citizen Scientist, Normandie, France
  • 61. Unistellar Citizen Scientist, Christchurch, New Zealand
  • 62. Unistellar Citizen Scientist, Austin, TX, USA
  • 63. Unistellar Citizen Scientist, Saint Paul les Dax, France
  • 64. Unistellar Citizen Scientist, Oakland, CA, USA
  • 65. Unistellar Citizen Scientist, Laren, Gelderland, The Netherlands
  • 66. Unistellar Citizen Scientist, Raleigh, NC, USA
  • 67. Unistellar Citizen Scientist, Longmont, CO, USA

Abstract

We report the discovery and confirmation of TOI-4465 b, a 1.25RJ^+(0.08 RJ)_(-0.07) RJ, 5.89MJ ± 0.26MJ giant planet orbiting a G dwarf star at d ≃ 122 pc. The planet was detected as a single-transit event in data from Sector 40 of the Transiting Exoplanet Survey Satellite (TESS) mission. Radial velocity (RV) observations of TOI-4465 showed a planetary signal with an orbital period of ∼102 days and an orbital eccentricity of e = 0.24 ± 0.01. TESS reobserved TOI-4465 in Sector 53 and Sector 80 but did not detect another transit of TOI-4465 b, as the planet was not expected to transit during these observations based on the RV period. A global ground-based photometry campaign was initiated to observe another transit of TOI-4465 b after the RV period determination. The ∼12 hr long transit event was captured from multiple sites around the world and included observations from 24 citizen scientists, confirming the orbital period as ∼102 days. TOI-4465 b is a relatively dense (3.73 ± 0.53 g cm−3), temperate (375–478 K) giant planet. Based on giant planet structure models, TOI-4465 b appears to be enriched in heavy elements at a level consistent with late-stage accretion of icy planetesimals. Additionally, we explore TOI-4465 b’s potential for atmospheric characterization and obliquity measurement. Increasing the number of long-period planets by confirming single-transit events is crucial for understanding the frequency and demographics of planet populations in the outer regions of planetary systems.

Copyright and License

© 2025. The Author(s). Published by the American Astronomical Society.

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

Z.E. acknowledges support from the TESS Guest Investigator Program grant 80NSSC23K0769. D.D. acknowledges support from the TESS Guest Investigator Program grant 80NSSC23K0769 and from the NASA Exoplanet Research Program grant 80NSSC20K0272. D.R.C. acknowledges partial support from NASA grant 18-2XRP18 2-0007. We thank Ken and Gloria Levy, who supported the construction of the Levy Spectrometer on the Automated Planet Finder. We thank the University of California and Google for supporting Lick Observatory and the UCO staff for their dedicated work scheduling and operating the telescopes of Lick Observatory. P.A.D. acknowledges support by a 51 Pegasi b Postdoctoral Fellowship from the Heising-Simons Foundation and by a National Science Foundation (NSF) Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. L.A.S. and T.M.E. were partially supported during this work by the NASA Citizen Science Seed Funding Program via grant No. 80NSSC22K1130 and the NASA Exoplanets Research Program via grant 80NSSC24K0165. Those NASA grants also support the UNITE (Unistellar Network Investigating TESS Exoplanets) program, under the auspices of which the Unistellar data were collected. The Unistellar Network also acknowledges financial support during its foundational phase from Frédéric Gastaldo and the Gordon and Betty Moore Foundation. We thank Niniane Leroux for her contributions to observations as a Unistellar Citizen Scientist. This work makes use of observations from the LCOGT network. Part of the LCOGT telescope time was granted by NOIRLab through the Mid-Scale Innovations Program (MSIP). MSIP is funded by NSF. This research has made use of the Exoplanet Follow-up Observation Program (ExoFOP; DOI:10.26134/ExoFOP5) 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 paper made use of data collected by the TESS mission and that are publicly available from the Mikulski Archive for Space Telescopes (MAST) operated by the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by NASA’s Science Mission Directorate. 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. K.A.C. and C.N.W. acknowledge support from the TESS mission via subaward s3449 from MIT. Some of the observations in this paper made use of the High-Resolution Imaging instrument ‘Alopeke and were obtained under Gemini LLP proposal No. GN/S-2021A-LP-105. ‘Alopeke was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Alopeke was mounted on the Gemini North telescope of the international Gemini Observatory, a program of NSF’s OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Some observations in this work were obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações (MCTI/LNA) do Brasil, the US National Science Foundation’s NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). I.A.S. (SAI speckle imaging) acknowledges the support of M. V. Lomonosov Moscow State University Program of Development. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). This work has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. This work is based in part on data collected under the NGTS project at the ESO La Silla Paranal Observatory. The NGTS facility is operated by a consortium of institutes with support from the UK Science and Technology Facilities Council (STFC) under projects ST/M001962/1, ST/S002642/1, and ST/W003163/1. The contributions at the Mullard Space Science Laboratory by E.M.B. have been supported by STFC through the consolidated grant ST/W001136/1. The postdoctoral fellowship of K.B. is funded by F.R.S.-FNRS grant T.0109.20 and by the Francqui Foundation.

Facilities

TESS - , LCOGT - Las Cumbres Observatory Global Telescope, NGTS - , Unistellar - , NEOSSat - , APF - , CTIO:1.5m (SMARTS 1.5m, CHIRON - ), FLWO:1.5m (TRES) - , Euler:1.2m (CORALIE) - , Keck:I - KECK I Telescope (HIRES), Gemini:Gillett - Gillett Gemini North Telescope (‘Alopeke), SOAR - The Southern Astrophysical Research Telescope, SAI - , Hale - Palomar Observatory's 5.1m Hale Telescope (PHARO).

Software References

AstroImageJ (K. A. Collins et al. 2017), TAPIR (E. Jensen 2013), juliet (N. Espinoza et al. 2019), dynesty (J. S. Speagle 2020). Lightkurve (Lightkurve Collaboration et al. 2018), PyLDTK (H. Parviainen 2015).

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2506.20019 (arXiv)
Is supplemented by
Dataset: 10.26134/ExoFOP5 (DOI)

Funding

National Aeronautics and Space Administration
80NSSC23K0769
National Aeronautics and Space Administration
80NSSC20K0272
National Aeronautics and Space Administration
18-2XRP18 2-0007
Heising-Simons Foundation
51 Pegasi b Postdoctoral Fellowship -
National Science Foundation
AST-1903811
National Aeronautics and Space Administration
80NSSC22K1130
National Aeronautics and Space Administration
80NSSC24K0165
Massachusetts Institute of Technology
s3449
Gemini Observatory
GN/S-2021A-LP-105
Swiss National Science Foundation
51NF40_182901
Swiss National Science Foundation
51NF40_205606
Science and Technology Facilities Council
ST/M001962/1
Science and Technology Facilities Council
ST/S002642/1
Science and Technology Facilities Council
ST/W003163/1
Science and Technology Facilities Council
ST/W001136/1
Fonds De La Recherche Scientifique - FNRS
T.0109.20
Fondation Francqui

Dates

Accepted
2025-05-12
Available
2025-06-25
Published

Caltech Custom Metadata

Caltech groups
Astronomy Department, Infrared Processing and Analysis Center (IPAC), Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published