TOI-858 B b: A hot Jupiter on a polar orbit in a loose binary^★,★★

¹ Départment d’astronomie de l’Université de Genève, Chemin Pegasi 51, 1290 Versoix, Switzerland
e-mail: janis.hagelberg@unige.ch
² European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
³ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
⁴ Department of Astrophysical Sciences, Princeton University, 4 Ivy Ln, Princeton, NJ 08544, USA
⁵ Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Pasadena, CA 91125, USA
⁶ Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
⁷ Center for Astrophysics – Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁸ Department of Astronomy, Yale University, 266 Whitney Avenue, New Haven, CT 06511, USA
⁹ El Sauce Observatory, Río Hurtado, Coquimbo Province, Chile
¹⁰ Bryant Space Science Center, Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
¹¹ Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
¹² European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile
¹³ Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, 120 E. Cameron Ave., Phillips Hall CB3255, Chapel Hill, NC 27599-3255, USA
¹⁴ Brierfield Observatory, Bowral NSW 2576, Australia
¹⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁶ Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
¹⁷ Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
¹⁸ Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
¹⁹ Department of Physics and Astronomy, Vanderbilt University, PMB 401807, 2301 Vanderbilt Place, Nashville, TN 37235, USA
²⁰ Hazelwood Observatory, Victoria, Australia
²¹ Department of Astronomy, Indiana University, 727 East 3rd Street, Swain West 318, Bloomington, IN 47405, USA
²² Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4, Canada

Received: 9 September 2022
Accepted: 17 August 2023

Abstract

We report the discovery of a hot Jupiter on a 3.28-day orbit around a 1.08 M_⊙ G0 star that is the secondary component in a loose binary system. Based on follow-up radial velocity observations of TOI-858 B with CORALIE on the Swiss 1.2 m telescope and CHIRON on the 1.5 m telescope at the Cerro Tololo Inter-American Observatory (CTIO), we measured the planet mass to be 1.10_−0.07^+0.08 M_J. Two transits were further observed with CORALIE to determine the alignment of TOI-858 B b with respect to its host star. Analysis of the Rossiter-McLaughlin signal from the planet shows that the sky-projected obliquity is λ = 99.3_−3.7^+3.8°. Numerical simulations show that the neighbour star TOI-858 A is too distant to have trapped the planet in a Kozai–Lidov resonance, suggesting a different dynamical evolution or a primordial origin to explain this misalignment. The 1.15 M_⊙ primary F9 star of the system (TYC 8501-01597-1, at ρ ~11″) was also observed with CORALIE in order to provide upper limits for the presence of aplanetary companion orbiting that star.