More Like this

1. Stellar Obliquities of Young Systems, Atmospheres Undergoing Contraction and Escape (SOYSAUCE): A Likely Aligned Orbit for the 3 Myr Planet TIDYE-1 b

   https://doi.org/10.3847/2041-8213/ae2004  

   Barber, Madyson G; Mann, Andrew W; Johnson, Marshall C; Mori, Mayuko; Livingston, John; Krolikowski, Daniel M; Narita, Norio; Fukui, Akihiko; Hirano, Teruyuki; Vanderburg, Andrew; et al (November 2025, The Astrophysical Journal Letters)

   Abstract Despite the wide range of planet–star (mis)alignments in the mature population of transiting exoplanets, the small number of known young transiting planets are nearly all aligned with the rotation axes of their host stars, as determined by the sky-projected obliquity angle. The small number of young systems with measured obliquities limits statistical conclusions. Here we determine the sky-projected obliquity (λ) of the 3 Myr transiting planet with a misaligned outer protoplanetary disk, TIDYE-1 b (IRAS 04125+2902b), using the Rossiter–McLaughlin (RM) effect. Our dataset lacks a pretransit baseline and ingress, complicating a blind RM fit. Instead, we use contemporaneous spectra and photometry from a mass-measurement campaign to model the stellar activity trend across the transit and provide an external prior on the velocity baseline. We determine $\mid \lambda \mid =11.8_{-5.0}^{+5.9}°$ . Combined with the published rotational velocity of the star, we find a true three-dimensional obliquity of $\psi =15.2_{-5.7}^{+7.3}°$ . Our result is consistent with an aligned orbit, suggesting the planet remains aligned to its star even though the outer disk is misaligned, though additional RM observations are needed to exclude the low-probability tail of misaligned (>30°) scenarios present in our posterior. 

   more » « less
2. The True Stellar Obliquity of a Sub-Saturn Planet from the Tierras Observatory and the Keck Planet Finder

   https://doi.org/10.3847/1538-3881/add530  

   Tamburo, Patrick; Yee, Samuel W; García-Mejía, Juliana; Stefánsson, Gudmundur; Charbonneau, David; Bieryla, Allyson; Howard, Andrew W; Isaacson, Howard; Fulton, Benjamin J; Householder, Aaron (June 2025, The Astronomical Journal)

   Abstract We measure the true obliquity of TOI-2364, a K dwarf with a sub-Saturn-mass (M_p = 0.18M_J) transiting planet on the upper edge of the hot-Neptune desert. We used new Rossiter–McLaughlin observations gathered with the Keck Planet Finder to measure the sky-projected obliquityλ = 7° + 10°–11°. Combined with a stellar rotation period of 23.47 ± 0.29 days measured with photometry from theTierrasObservatory, this yields a stellar inclination of 90° ± 13° and a true obliquityψ = 15 $\stackrel{\text{°}}{.}$ 6 + 7 $\stackrel{\text{°}}{.}$ 7–7 $\stackrel{\text{°}}{.}$ 3, indicating that the planet’s orbit is well aligned with the rotation axis of its host star. The determination ofψis important for investigating a potential bimodality in the orbits of short-period sub-Saturns around cool stars, which tend to be either aligned with or perpendicular to their host stars’ spin axes. 

   more » « less
3. The OATMEAL Survey. II. The 3D Spin–Orbit Obliquity of an Eccentric Transiting Brown Dwarf in the Ruprecht 147 Open Cluster

   https://doi.org/10.3847/1538-3881/ae19e8  

   Carmichael, Theron W; Giacalone, Steven; Vowell, Noah; Huber, Daniel; Wang, Xian-Yu; Bossett, Malik; Handley, Luke; Householder, Aaron; Li, Yaguang; Fulton, Benjamin J; et al (December 2025, The Astronomical Journal)

   Abstract We present a new analysis of the CWW 89 system as part of the Orbital Architectures of Transiting Massive Exoplanets And Low-mass stars (OATMEAL) survey. The CWW 89 system is a member of the 2.8 Gyr old Ruprecht 147 (NGC 6774) cluster and consists of two stars, CWW 89A (EPIC 219388192) and CWW 89B, with the primary hosting a transiting brown dwarf, CWW 89Ab. We use in-transit, highly precise radial velocity measurements with the Keck Planet Finder to characterize the Rossiter–McLaughlin (RM) effect and measure the projected spin–orbit obliquity ∣λ∣ = 1 $\stackrel{\text{°}}{.}$ 4 ± 2 $\stackrel{\text{°}}{.}$ 5 and the full 3D spin–orbit obliquity of the brown dwarf to be $\psi =15.1_{-10.9}^{+15.0^{\circ }}$ . This value ofλimplies that the brown dwarf’s orbit is prograde and well-aligned with the equator of the host star, continuing the trend of transiting brown dwarfs showing a preference for spin–orbit alignment (λ ≈ 0°) regardless of the stellar effective temperature. This contrast with the transiting giant planet population, whose spin–orbit alignments depend on hostT_eff, shows an increasingly clear distinction in the formation and orbital migration mechanisms between transiting giant planets and transiting brown dwarfs like CWW 89Ab. For this system in particular, we find it plausible that the brown dwarf may have undergone coplanar high-eccentricity migration influenced by CWW 89B. 

   more » « less
4. The Polar Orbit of TOI-2374 b, a Planet in the Neptunian Ridge

   https://doi.org/10.3847/1538-3881/ae070b  

   Yee, Samuel W; Tamburo, Patrick; Stefánsson, Gudmundur; García-Mejía, Juliana; Charbonneau, David; Barkaoui, Khalid; Collins, Karen A; Schwarz, Richard P; Narita, Norio; Fukui, Akihiko; et al (October 2025, The Astronomical Journal)

   Abstract The “Neptunian ridge” is a recently identified peak in the frequency of planets with sizes between that of Neptune and Saturn orbiting their host stars with periods between 3 and 6 days. These planets may have formed similarly to their larger, hot Jupiter counterparts in the “3 day pileup,” through a dynamically excited migration pathway. The distribution of stellar obliquities in hot Neptune systems may therefore provide a vital clue as to their origin. We report a new stellar obliquity measurement for TOI-2374b, a planet in the Neptunian ridge (P= 4.31 days,R_p = 7.5R_⊕). We observed a spectroscopic transit of TOI-2374b with the Keck Planet Finder, detecting the Rossiter–McLaughlin (RM) anomaly with an amplitude of 3 m s⁻¹, and measured a sky-projected obliquity of $\lambda ={81°}_{-22^{\circ }}^{+23^{\circ }}$ , indicating an orbit significantly misaligned with the spin axis of its host star. A reloaded RM analysis of the cross-correlation functions confirms this misalignment, measuring $\lambda ={65°}_{-24^{\circ }}^{+32^{\circ }}$ . Additionally, we measured a stellar rotation period of $P_{\mathrm{rot}}=26.4_{-0.8}^{+0.9}$ days with photometry from theTierrasobservatory, allowing us to deduce the three-dimensional stellar obliquity of $\psi ={85\stackrel{°}{.}9}_{-9\stackrel{°}{.}2}^{+8\stackrel{°}{.}6}$ . TOI-2374b joins a growing number of hot Neptunes on polar orbits. The high frequency of misaligned orbits for Neptunian ridge and desert planets, compared with their longer period counterparts, is reminiscent of patterns seen for the giant planets and may suggest a similar formation mechanism. 

   more » « less
5. The Super-puff WASP-193 b is on a Well-aligned Orbit*

   https://doi.org/10.3847/1538-3881/adba5f  

   Yee, Samuel W; Stefánsson, Gudmundur; Thorngren, Daniel; Monson, Andy; Hartman, Joel D; Charbonneau, David B; Teske, Johanna K; Butler, R Paul; Crane, Jeffrey D; Osip, David; et al (March 2025, The Astronomical Journal)

   Abstract The “super-puffs” are a population of planets that have masses comparable to that of Neptune but radii similar to Jupiter, leading to extremely low bulk densities (ρ_p ≲ 0.2 g cm⁻³) that are not easily explained by standard core accretion models. Interestingly, several of these super-puffs are found in orbits significantly misaligned with their host stars’ spin axes, indicating past dynamical excitation that may be connected to their low densities. Here, we present new Magellan/Planet Finder Spectrograph radial velocity measurements of WASP-193, a late F star hosting one of the least dense transiting planets known to date ( $M_p=0.112_{-0.034}^{+0.029}{M}_{\mathrm{J}}$ , $R_p=1.319_{-0.048}^{+0.056}{R}_{\mathrm{J}}$ ,ρ_p = 0.060 ± 0.019 g cm⁻³). We refine the bulk properties of WASP-193 b and use interior structure models to determine that the planet can be explained if it consists of roughly equal amounts of metals and H/He, with a metal fraction ofZ= 0.42. The planet is likely substantially reinflated due to its host star’s evolution, and expected to be actively undergoing mass loss. We also measure the projected stellar obliquity using the Rossiter–McLaughlin effect, finding that WASP-193 b is on an orbit well aligned with the stellar equator, with $\lambda =16_{-15}^{+16}$ degrees. WASP-193 b is the first Jupiter-sized super-puff on a relatively well-aligned orbit, suggesting a diversity of formation pathways for this population of planets. 

   more » « less