Matthew. R. Burleigh

HAT-P-26,b is a well-characterized Neptunian exoplanet ̊m p R_⊕) orbiting a K1V star. It lies within the Neptunian ridge (P_ ̊m orb days), following a moderately eccentric orbit (e and hosting a water-rich atmosphere. The possible presence of a stellar companion hinted at by near-infrared (NIR) spectral emission, along with candidate planetary companions inferred from transit timing variations, calls for further investigations of the system architecture. Hence, the HAT-P-26 system is a prominent target for investigating the atmospheric and dynamical evolution of exo-Neptunes and, in particular, via the study carried out by the Ancestry, Traits, and Relations of Exoplanets Inhabiting the Desert Edges and Savanna (ATREIDES) collaboration. We combined three transit observations of HAT-P-26,b using ESPRESSO on ESO's VLT to precisely characterize its orbital architecture and to investigate whether it has a misaligned orbit, as reported in cases of other evaporating and eccentric planets in the ridge. We employed the workflow to perform a careful and robust data reduction. We explored the system's orbital architecture using the in-built Rossiter-McLaughlin Revolutions (RMR) technique. ANTARESS HAT-P-26,b exhibits a polar orbit (projected obliquity angle of łambda = -78_ -13 ^ +13 ^ ̧irc and a 3D true obliquity angle of ψ = 85_ -5 ^ +5 ^̧irc). This places it alongside GJ,436,b, HAT-P-11,b, and GJ,3470,b as polar-orbit and eccentric planets lying within the ridge population. It has the lowest density (0.40 ) of these four planets, placing it near the density brink where full atmospheric erosion after early disk-driven migration or tidal disruption after high-eccentricity migration has been proposed to occur. Our dynamical analysis suggests that the observed polar orbit might either be a transient state arising from orbital-plane precession or a relic of high-eccentricity migration via Von Zeipel–Lidov–Kozai cycles driven by an inclined stellar companion. We note that in the latter case, the existence of planet,c would be strongly disfavored. g cm^ -3 HAT-P-26,b stands out as a special target in the Neptunian ridge, owing to its low density and polar orbit. The current dynamical analysis is limited by the uncertainties surrounding companion(s) in this system. As better constraints on the companion(s) become available, it will be particularly interesting to further explore the origin of this fluffy ridge Neptune through a joint analysis of migration, evaporation, tidal disruption, and inflation. Our results also demonstrate the importance of homogeneous data reduction when combining multi-epoch transit observations for accurate spin-orbit characterization.

We identify two large-radius planets around the F-type star HD 114082 as the longest-period young transiting exoplanets known. From the first transit, detected by NASA’s Transiting Exoplanet Survey Satellite (TESS), and a second dip, spotted by the Next-Generation Transit Survey (NGTS), we predicted midtransit times for HD 114082 b (planet b). We pinpoint its orbit (period P _b = 225.5504 ± 0.0004 days) from a third transit captured with the ESA’s CHaracterising ExOplanet Satellite and the upgraded Antarctic Search for Transiting ExoPlanets telescope (ASTEP+), alongside orbit-discriminating observations. Another dimming partly covered by ASTEP+ completes the four-transit series. We support with dynamical evidence the planetary nature of a deeper transit detected with TESS and NGTS, identifying planet c. Additionally, we reexamine the debris disk, fitting its excess emission with two dust components. Fundamental stellar parameters are inferred from stellar evolution models, while a joint modeling of photometric and radial velocity time series yields the planetary parameters, with masses further constrained using an N-body code. For planet b, the semimajor axis a _b = 0.791 ± 0.008 au, eccentricity e _b ≈0, inclination i _b = 89 . ° 791 ±0.014, radius R _b = 1.046 ± 0.014 R _J , and 95% confidence upper limit on its mass M _95%,b = 1.6 M _J . For planet c, a _c = 0.99 − 0.04 + 0.03 au, e _c ≈0, i _c = 89 . ° 701 ±0.011, R _c = 1.36±0.03 R _J , and M _95%,c = 2.0 M _J (0.24 M _J if adding transit-timing-variation constraints). They seem to be moderate-to-low-mass giants in nearly resonant, coplanar, circular orbits that formed in situ, or beyond the snow line, and migrated inward, shaping the disk.

Observations have shown that planets similar to Neptune are rarely found orbiting Sun-like stars with periods up to ∼4 days. This defines the so-called Neptune desert region. The detection of each individual planet in this region therefore holds a high value by providing detailed insights into the formation and evolution of this population. We report the detection of TOI-333b, a Neptune-desert planet with a mass, radius, and bulk density of 20.1 ± 2.4 M _⊕ , 4.26 ± 0.11 R _⊕ , and 1.42 ± 0.21 g cm ⁻³ . The planet orbits an F7V star every 3.78 d, whose mass, radius, and effective temperature are of 1.2 ± 0.1 M _⊙ , 1.10 ± 0.03 R _⊙ , and 6241 ₋₆₂ ⁺⁷³ K, respectively. TOI-333bis likely younger than 1 Gyr, which is supported by the doublet Li line around 6707.856 Å and its comparison to Li abundances in open clusters with well-constrained ages. The planet is expected to host only a 8.5 _−8.3 ^+10.9 % gas-to-core mass ratio for an H/He envelope. On the other hand, models of irradiated ocean worlds predict a 20 ₋₁₀ ⁺¹¹ % H ₂ O mass fraction with a core fraction of 35 ₋₂₃ ⁺²⁰ %. We therefore expect that the internal composition of TOI-333bis dominated by a pure rocky composition with almost no H/He envelope, or a rocky world with almost equal mass fraction of water. Finally, TOI-333bis more massive and larger than 77% and 82% of its Neptune-desert counterparts, and its host ranks among the hottest known stars for Neptune-desert planets. This makes this system a unique laboratory for studying the evolution of these planets around hot stars.