Browsing by Author "Stefánsson, Guðmundur"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The Aligned Orbit of the Eccentric Proto Hot Jupiter TOI-3362b
    (2023) Espinoza Retamal, Juan; Brahm, Rafael; Petrovich, Cristobal; Jordán, Andrés; Stefánsson, Guðmundur; Sedaghati, Elyar; Hobson, Melissa J.; Muñoz, Diego J.; Boyle, Gavin; Leiva, Rodrigo; Suc, Vincent
    High-eccentricity tidal migration predicts the existence of highly eccentric proto-hot Jupiters on the "tidal circularization track," meaning that they might eventually become hot Jupiters, but that their migratory journey remains incomplete. Having experienced moderate amounts of the tidal reprocessing of their orbital elements, proto-hot Jupiters systems can be powerful test-beds for the underlying mechanisms of eccentricity growth. Notably, they may be used for discriminating between variants of high-eccentricity migration, each predicting a distinct evolution of misalignment between the star and the planet's orbit. We constrain the spin-orbit misalignment of the proto-hot Jupiter TOI-3362b with high-precision radial velocity observations using ESPRESSO at VLT. The observations reveal a sky-projected obliquity $\lambda = 1.2_{-2.7}^{+2.8}$ deg and constrain the orbital eccentricity to $e=0.720 \pm 0.016$, making it one of the most eccentric gas giants for which the obliquity has been measured. The large eccentricity and the striking orbit alignment of the planet suggest that ongoing coplanar high-eccentricity migration driven by a distant companion is a likely explanation for the system's architecture. This distant companion would need to reside beyond 5 au at 95% confidence to be compatible with the available radial velocity observations....
  • Thumbnail Image
    Item
    The Spin–Orbit Alignment of Eight Warm Gas Giant Systems
    (American Astronomical Society, 2025) Espinoza Retamal, Juan Ignacio; Jordán Colzani, Andrés Cristóbal; Brahm Scott, Rafael; Petrovich Balbontín, Cristóbal; Sedaghati, Elyar; Stefánsson, Guðmundur; Hobson, Melissa J.; Tala Pinto, Marcelo Said; Muñoz, Diego J.; Boyle, Gavin; Leiva, Rodrigo; Suc, Vincent
    Essential information about the formation and evolution of planetary systems can be found in their architectures—in particular, in stellar obliquity (ψ)—as they serve as a signature of their dynamical evolution. Here we present ESPRESSO observations of the Rossiter–McLaughlin (RM) effect of eight warm gas giants, revealing that, independently of the eccentricities, all of them have relatively aligned orbits. Our five warm Jupiters (WASP-106 b, WASP-130 b, TOI-558 b, TOI-4515 b, and TOI-5027 b) have sky-projected obliquities |λ| ≃ 0–10°, while the two less massive warm Saturns (K2-139 b and K2-329 A b) are slightly misaligned, having |λ| ≃ 15–25°. Furthermore, for K2-139 b, K2-329 A b, and TOI-4515 b, we also measure true 3D obliquities ψ ≃ 15–30°. We also report a nondetection of the RM effect produced by TOI-2179 b. Through hierarchical Bayesian modeling of the true 3D obliquities of hot and warm Jupiters, we find that around single stars warm Jupiters are statistically more aligned than hot Jupiters. Independent of eccentricities, 95% of the warm Jupiters have ψ ≲ 25° with no misaligned planets, while hot Jupiters show an almost isotropic distribution of misaligned systems. This implies that around single stars warm Jupiters form in primordially aligned protoplanetary disks and subsequently evolve in a more quiescent way than hot Jupiters. Finally, we find that Saturns may have slightly more misaligned orbits than warm Jupiters, but more obliquity measurements are necessary to be conclusive.