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Published December 20, 2025 | Version Published
Journal Article Open

HD 143811 AB b: A Directly Imaged Planet Orbiting a Spectroscopic Binary in Sco-Cen

Creators

  • 1. ROR icon Northwestern University
  • 2. ROR icon New Mexico State University
  • 3. ROR icon European Southern Observatory
  • 4. ROR icon University of California, San Diego
  • 5. ROR icon University of California, Santa Cruz
  • 6. ROR icon University of California, Los Angeles
  • 7. ROR icon Lawrence Livermore National Laboratory
  • 8. ROR icon Jet Propulsion Lab
  • 9. ROR icon University of Arizona
  • 10. ROR icon University of Hawaii at Manoa
  • 11. ROR icon University of California, Berkeley
  • 12. ROR icon University of Notre Dame
  • 13. ROR icon Institut de Planétologie et d'Astrophysique de Grenoble
  • 14. ROR icon Search for Extraterrestrial Intelligence
  • 15. ROR icon Amherst College
  • 16. ROR icon Durham University
  • 17. Gemini Observatory, Casilla 603, La Serena, Chile
  • 18. ROR icon Infrared Processing and Analysis Center
  • 19. Vera C. Rubin Observatory, 950 N Cherry Ave., Tucson AZ 85719, USA
  • 20. ROR icon National Research Council Canada
  • 21. ROR icon University of Victoria
  • 22. ROR icon California Institute of Technology
  • 23. ROR icon Western University
  • 24. ROR icon University of California, Santa Barbara
  • 25. ROR icon American Museum of Natural History
  • 26. ROR icon Arizona State University
  • 27. ROR icon Space Telescope Science Institute
  • 28. ROR icon University of Montreal
  • 29. ROR icon Observatoire de la Côte d'Azur
  • 30. ROR icon Cornell University
  • 31. ROR icon United States Naval Observatory
  • 32. ROR icon George Mason University
  • 33. ROR icon University of Georgia
  • 34. ROR icon Smith College

Abstract

We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the GPI Exoplanet Survey in 2016 and 2019 and is a member of the Sco-Cen star formation region. The exoplanet is detected ∼430 mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semimajor axis of 64⁺³²₋₁₄ au and eccentricity 0.23^(+0.24)_(-0.16). Spectral analysis of the GPI H -band spectrum and NIRC2 L′ photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-Radioactive-Convective Equilibrium Model (REM) exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of 1042⁺¹⁷⁸₋₁₃₂ for the planet and translate the derived luminosity of the planet to a mass of 5.6 ± 1.1 M_(Jup) assuming hot-start evolutionary models. HD 143811 AB b is the first directly imaged planet around a binary that is not on an ultrawide orbit. Future characterization of this object will shed light on the formation of planets around binary star 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

We thank the anonymous referee for helpful suggestions in preparing the final version of this Letter.

N.J. acknowledges the BOBA group for their help and support throughout the preparation and publication of this project. Additionally, N.J. would like to acknowledge and thank their kūpuna, ‘ohana, and the ‘āina of Hawai‘i Island on which part of this work took place.

J.J.W. acknowledges support from the Alfred P. Sloan Foundation.

The Gemini Observatory is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciéncia, Tecnologia e Inovaçāo (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant No. ACI-1548562.

Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO program(s) 0101.A-9012(A), 0107.A-9004(A), 0109.A-9014(A). This research has made use of the SIMBAD database, CDS, Strasbourg Astronomical Observatory, France. This research has made use of the VizieR catalog access tool, CDS, Strasbourg Astronomical Observatory, France (F. Ochsenbein et al. 2000).

This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

This research was funded in part by the Gordon and Betty Moore Foundation through grant GBMF8550 to M.L.

This material is based on work supported by the National Science Foundation Graduate Research Fellowship under grant No. 2139433 to A.S.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 to S.M A.

This work has benefited from The UltracoolSheet at http://bit.ly/UltracoolSheet, maintained by Will Best, Trent Dupuy, Michael Liu, Aniket Sanghi, Rob Siverd, and Zhoujian Zhang, and developed from compilations by T. J. Dupuy & M. C. Liu (2012), T. J. Dupuy & A. L. Kraus (2013), N. R. Deacon et al. (2014), M. C. Liu et al. (2016), W. M. J. Best et al. (2018), W. M. J. Best et al. (2021), A. Sanghi et al. (2023), and A. C. Schneider et al. (2023).

Facilities

Keck:II - KECK II Telescope (NIRC2), Gemini:South - (GPI).

Software References

GPI Data Reduction Pipeline (M. D. Perrin et al. 2014, 2016), pyKLIP (J. J. Wang et al. 2015), VIP (C. A. Gomez Gonzalez et al. 2017; V. Christiaens et al. 2023), emcee (D. Foreman-Mackey et al. 2013), dynesty (J. S. Speagle 2020; S. Koposov et al. 2024), species (T. Stolker et al. 2020), astropy (Astropy Collaboration et al. 2013, 2018, 2022), numpy (C. R. Harris et al. 2020), matplotlib (J. D. Hunter 2007).

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2509.06729 (arXiv)
Is supplemented by
Dataset: http://bit.ly/UltracoolSheet (URL)

Funding

Alfred P. Sloan Foundation
National Energy Research Scientific Computing Center
DE-AC02-05CH11231
National Science Foundation
ACI-1548562
Gordon and Betty Moore Foundation
GBMF8550
National Science Foundation
2139433
United States Department of Energy
DE-AC52-07NA27344

Dates

Submitted
2025-08-29
Accepted
2025-11-15
Available
2025-12-11
Published

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