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arXiv · 2606.09973

Stellar Obliquities of Young Systems, Atmospheres Undergoing Contraction and Escape (SOYSAUCE) II: a 135 Myr planet on an aligned orbit with transit timing variations

Madyson G. Barber·Andrew W. Mann·Sydney Vach·Leah J. Boff·Andrew W. Boyle·Andrew Vanderburg·Adam L. Kraus·Benjamin M. Tofflemire·Marshall C. Johnson·Allyson Bieryla·David W. Latham·Karen A. Collins·Steve B. Howell·Richard P. Schwarz·Gregorg Srdoc·Francis P. Wilkin·Felipe Murgas·Enric Palle·Chris Stockdale
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Abstract

Young planets (<1 Gyr) provide opportunities to directly probe planet formation and evolution processes in action. However, due to heightened stellar activity, there is a lack of known transiting planets in adolescence (~100-500 Myr). Here we present the validation of TIC 150070085 b, a 3.6 R_E planet on a 10.47 day orbit, and report the candidate TIC 150070085 c, a 3.0 R_E planet on a 15.90 day orbit. While we are unable to validate the second signal, the proximity to mean motion resonance (3:2) and transit timing variations observed in the transits of TIC 150070085 b strongly suggest the signal is planetary. We confirm the host star as a member of Alessi 84 and combine the group's CMD, rotation, and variability properties to update the age to 135 +/- 10 Myr. We additionally use MAROON-X to observe the Rossiter-McLaughlin signal of TIC 150070085 b and measure the sky projected obliquity angle ($λ$). We find TIC 150070085 b is consistent with a near-aligned orbit with its host star (|$λ$| = 18 +/- 12$^\circ$), in line with similarly aged transiting planets with measured $λ$ values. Continued discovery and characterization of planets in this age regime are vital to link planetary infancy (<50 Myr) and maturity (>1 Gyr).

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Madyson G. Barber, Andrew W. Mann, Sydney Vach, Leah J. Boff, Andrew W. Boyle, Andrew Vanderburg, Adam L. Kraus, Benjamin M. Tofflemire, Marshall C. Johnson, Allyson Bieryla, David W. Latham, Karen A. Collins, Steve B. Howell, Richard P. Schwarz, Gregorg Srdoc, Francis P. Wilkin, Felipe Murgas, Enric Palle, Chris Stockdale. 2026-06-08. Stellar Obliquities of Young Systems, Atmospheres Undergoing Contraction and Escape (SOYSAUCE) II: a 135 Myr planet on an aligned orbit with transit timing variations. https://arxiv.org/abs/2606.09973

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