NEID Reveals That the Young Warm Neptune TOI-2076 b Has a Low Obliquity
Mahadevan, Suvrath; Wisniewski, John; Wright, Jason T.; Winn, Joshua N.; Dai, Fei; McElwain, Michael W.; Cañas, Caleb I.; Kanodia, Shubham; Ninan, Joe P.; Hebb, Leslie; Bender, Chad F.; Halverson, Samuel; Robertson, Paul; Roy, Arpita; Schwab, Christian; Terrien, Ryan C.; Lin, Andrea S. J.; Holcomb, Rae; Stefánsson, Gudmundur; Dong, Jiayin; Libby-Roberts, Jessica; Gupta, Arvind F.; Doyle, Lauren; Yee, Samuel W.; Kowalski, Adam; Petrovich, Cristobal; Hawley, Suzanne; Luhn, Jacob; Cegla, Heather; Frazier, Robert C.
United States, Sweden, Switzerland, United Kingdom, India, Chile, Australia
Abstract
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.