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

Abstract

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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>6</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>32</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> au and eccentricity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.23</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.24</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>104</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>132</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>178</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> K 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.

Affiliated Institutions

• University of California, Berkeley US
• Western University CA
• Amherst College US
• University of California, Los Angeles US
• Jet Propulsion Laboratory US
• Space Telescope Science Institute US
• European Southern Observatory CL
• California Institute of Technology US
• American Museum of Natural History US
• United States Naval Observatory US
• Planetary Science Institute US
• Infrared Processing and Analysis Center US
• University of Victoria CA
• University of Georgia US
• Centre National de la Recherche Scientifique FR
• Université Grenoble Alpes FR
• Northwestern University US
• Arizona State University US
• University of California, Santa Cruz US
• University of Arizona US
• Lawrence Livermore National Laboratory US
• Deleted Institution
• Observatoire de la Côte d’Azur FR
• Herzberg Institute of Astrophysics CA
• New Mexico State University US
• University of California, San Diego US
• Smith College US
• Université de Montréal CA
• University of California, Santa Barbara US
• Foundation for Research and Technology Hellas GR
• Cornell University US
• George Mason University US
• Durham University GB
• University of Hawaii System US
• University of Notre Dame US
• Search for Extraterrestrial Intelligence US

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