NEID Reveals That the Young Warm Neptune TOI-2076 b Has a Low Obliquity
Robert C. Frazier, Guðmundur Stefánsson, Suvrath Mahadevan, Samuel W. Yee, Caleb I. Cañas, Joshua N. Winn, Jacob K. Luhn, Fei Dai, Lauren Doyle, H. M. Cegla, Shubham Kanodia, Paul Robertson, John P. Wisniewski, Chad F. Bender, Jiayin Dong, Arvind F. Gupta, Samuel Halverson, Suzanne L. Hawley, Leslie Hebb, Rae Holcomb, Adam F. Kowalski, Jessica E. Libby-Roberts, Andrea S. J. Lin, Michael W. McElwain, Joe P. Ninan, Cristóbal Petrovich, Arpita Roy, Christian Schwab, Ryan C. Terrien, Jason T. Wright
Abstract
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>λ</mml:mi> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>16</mml:mn> <mml:mo>°</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> . 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ψ</mml:mi> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>18</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>10</mml:mn> <mml:mo>°</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> ( 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.