The Astrophysical Journal Letters (Jan 2023)

NEID Reveals That the Young Warm Neptune TOI-2076 b Has a Low Obliquity

  • Robert C. Frazier,
  • Gudmundur Stefánsson,
  • Suvrath Mahadevan,
  • Samuel W. Yee,
  • Caleb I. Cañas,
  • Joshua N. Winn,
  • Jacob Luhn,
  • Fei Dai,
  • Lauren Doyle,
  • Heather Cegla,
  • Shubham Kanodia,
  • Paul Robertson,
  • John Wisniewski,
  • Chad F. Bender,
  • Jiayin Dong,
  • Arvind F. Gupta,
  • Samuel Halverson,
  • Suzanne Hawley,
  • Leslie Hebb,
  • Rae Holcomb,
  • Adam Kowalski,
  • Jessica Libby-Roberts,
  • Andrea S. J. Lin,
  • Michael W. McElwain,
  • Joe P. Ninan,
  • Cristobal Petrovich,
  • Arpita Roy,
  • Christian Schwab,
  • Ryan C. Terrien,
  • Jason T. Wright

DOI
https://doi.org/10.3847/2041-8213/acba18
Journal volume & issue
Vol. 944, no. 2
p. L41

Abstract

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TOI-2076 b is a sub-Neptune-sized planet ( R = 2.39 ± 0.10 R _⊕ ) that transits a young (204 ± 50 MYr) bright ( V = 9.2) K-dwarf hosting a system of three transiting planets. Using spectroscopic observations obtained with the NEID spectrograph on the WIYN 3.5 m Telescope, we model the Rossiter–McLaughlin effect of TOI-2076 b, and derive a sky-projected obliquity of $\lambda =-{3}_{-15}^{+16^\circ }$ . Using the size of the star ( R = 0.775 ± 0.015 R _⊙ ), and the stellar rotation period ( P _rot = 7.27 ± 0.23 days), we estimate an obliquity of $\psi ={18}_{-9}^{+10^\circ }$ ( ψ < 34° at 95% confidence), demonstrating that TOI-2076 b is in a well-aligned orbit. Simultaneous diffuser-assisted photometry from the 3.5 m telescope at Apache Point Observatory rules out flares during the transit. TOI-2076 b joins a small but growing sample of young planets in compact multi-planet systems with well-aligned orbits, and is the fourth planet with an age ≲300 Myr in a multi-transiting system with an obliquity measurement. The low obliquity of TOI-2076 b and the presence of transit timing variations in the system suggest the TOI-2076 system likely formed via convergent disk migration in an initially well-aligned disk.

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