TOI-942b: A Prograde Neptune in a ~60 Myr old Multi-transiting System

Abstract

Mapping the orbital obliquity distribution of young planets is one avenue towards understanding mechanisms that sculpt the architectures of planetary systems. TOI-942 is a young field star, with an age of ~60 Myr, hosting a planetary system consisting of two transiting Neptune-sized planets in 4.3- and 10.1-day period orbits. We observed the spectroscopic transits of the inner Neptune TOI-942b to determine its projected orbital obliquity angle. Through two partial transits, we find the planet to be in a prograde orbit, with a projected obliquity angle of |lambda| = 1/+41-33 deg. In addition, incorporating the light curve and the stellar rotation period, we find the true three-dimensional obliquity to be 2/+27-23 deg. We explored various sources of uncertainties specific to the spectroscopic transits of planets around young active stars, and showed that our reported obliquity uncertainty fully encompassed these effects. TOI-942b is one of the youngest planets to have its obliquity characterized, and one of even fewer residing in a multi-planet system. The prograde orbital geometry of TOI-942b is in line with systems of similar ages, none of which have yet been identified to be in strongly misaligned orbits.

Accepted by ApJL, 10 pages, 5 figures

References in corpus (12)

• Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star
• On the Inference of a Star's Inclination Angle from its Rotation Velocity and Projected Rotation Velocity
• Limits on the Spin-Orbit Angle and Atmospheric Escape for the 22 Myr-old Planet AU Mic b
• The Habitable-zone Planet Finder Reveals A High Mass and a Low Obliquity for the Young Neptune K2-25b
• Two young planetary systems around field stars with ages between 20-320 Myr from TESS
• The TESS-Keck Survey IV: A Retrograde, Polar Orbit for the Ultra-Low-Density, Hot Super-Neptune WASP-107b
• Spin-orbit alignment and magnetic activity in the young planetary system AU Mic
• The GAPS Programme at TNG XXVIII -- A pair of hot-Neptunes orbiting the young star TOI-942
• Contemporaneous Imaging Comparisons of the Spotted Giant $\sigma$ Geminorum Using Interferometric, Spectroscopic, and Photometric Data
• The misaligned orbit of the Earth-sized planet Kepler-408b
• Spin-orbit alignment of the $\beta$ Pictoris planetary system
• The Young Planet DS Tuc Ab has a Low Obliquity

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• ATREIDES I. Embarking on a trek across the exo-Neptunian landscape with the TOI-421 system
• Evidence for Primordial Alignment II: Insights from Stellar Obliquity Measurements for Hot Jupiters in Compact Multiplanet Systems
• A sub-Neptune transiting the young field star HD 18599 at 40 pc