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

TOI-2076 b is a sub-Neptune-sized planet (R= 2.39 ± 0.10R) 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 ofλ=315+16°. Using the size of the star (R= 0.775 ± 0.015R), and the stellar rotation period (Prot= 7.27 ± 0.23 days), we estimate an obliquity ofψ=189+10°(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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Publication Date:
Journal Name:
The Astrophysical Journal Letters
Page Range or eLocation-ID:
Article No. L41
DOI PREFIX: 10.3847
Sponsoring Org:
National Science Foundation
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