Thomas G. Wilson

We present a Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) G141 phase-curve observation of the ultrashort-period rocky planet TOI-2431 b and detect its secondary eclipse in the near-infrared. Combined with the TESS optical eclipse, these measurements constrain the planet’s dayside brightness temperature, reflected light contribution, albedo, and heat redistribution. We detect the eclipse in the optical and near-infrared wavelengths of TESS and HST/WFC3 G141, with a planet-to-star flux ratio of 37 ± 10 ppm and 6 9 − 13 + 14 ppm , respectively. Assuming negligible reflected light, the joint TESS+HST fit yields a brightness temperature T b , joint = 252 4 − 84 + 77 K and a brightness temperature ratio of R joint = T b , joint / T p , max = 0.98 0 − 0.034 + 0.032 consistent with the zero-albedo, no-redistribution limit T p , max = 257 4 − 35 + 36 K . The HST phase curve is consistent with zero nightside emission and no measurable hotspot offset, consistent with inefficient day-night heat distribution. Under this thermal-dominated interpretation, TOI-2431 b lies at the zero-albedo, no-redistribution limit and contrasts with previously observed lava worlds. At optical and near-infrared wavelengths, however, thermal emission is degenerate with reflected light. For a geometric albedo of A _g = 0.1, reflected light would contribute approximately 11 ppm in each bandpass, reducing the temperature to T b , joint ( A g = 0.1 ) = 240 7 − 102 + 91 K . Longer-wavelength observations are required to isolate the thermal component. Planned JWST/MIRI LRS observations are expected to substantially reduce this degeneracy and provide more direct constraints on heat redistribution and possible silicate-atmosphere spectral features. This marks the first secondary eclipse detection of a rocky exoplanet using HST and establishes TOI-2431 b as a benchmark target for studying properties of lava worlds.

We present new CHEOPS transit observations of AU Mic b and AU Mic c obtained between June and September 2024, extending the baseline of transit-timing measurements of this young planetary system. For AU Mic b, the timing signal is well established, with a semi-amplitude (10 ± 3 min) and a characteristic modulation timescale (1168 ± 20 d) consistent with previous determinations. By contrast, the new CHEOPS data show that the large transit-timing deviation of AU Mic c reported previously was not sustained. After the steadily increasing timing trend observed in 2022 and 2023, the 2024 timings returned closer to the zero point of the observed-minus-calculated diagram, indicating a reversal of the previously reported behavior. For AU Mic c, both the transit-timing semi-amplitude (46 ± 26 min) and the characteristic modulation timescale (2150 ± 110 d) remain tentative. These results highlight the importance of continued long-term monitoring of the AU Mic system.

Context. The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. Aims. We present an extended radial velocity (RV) monitoring of the bright star K2-312≡HD 80653, known to host a rocky USP super-Earth ( P _b = 0.720 d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312 c. We aim to refine the orbital parameters of K2-312 c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system. Methods. We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression. Results. K2-312 c is a cold Jupiter on a wide orbit (orbital period refined to P _c = 871.32 d), with a minimum mass of M _c sin i ~5 M _Jup and a refined eccentricity of e _c ~ 0.85. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312 c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312 b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312 b.

We present the discovery of the planetary system orbiting the bright ( V = 7.2), nearby (35 pc), Sun-like ( M _⋆ = 1.050 ± 0.044 M _⊙ , R _⋆ = 1.129 ± 0.013 R _⊙ ) star, HD 60779. We report two Transiting Exoplanet Survey Satellite transits and a subsequent Characterising Exoplanet Satellite transit of HD 60779 b, a sub-Neptune ( 3.24 6 − 0.097 + 0.100 R ⊕ ) planet on a 29.98617 5 − 0.000033 + 0.000030 day orbit. Additionally, 313 High Accuracy Radial velocity Planet Searcher for the Northern hemisphere radial velocity (RV) measurements reveal the mass of planet b ( 14.1 9 − 0.96 + 0.97 M ⊕ ) and the presence of an outer planet, HD 60779 c ( P _orb = 104.79 ± 0.23 days, M p sin i = 28.3 ± 1.5 M ⊕ ). Both of these planets’ orbits are consistent with being circular, suggesting that they have a dynamically quiet history. The data are not sufficient to determine whether planet c transits. HD 60779’s uniquely high systemic RV (129.75 ± 0.12 km s ⁻¹ ) allows its Ly α emission to avoid absorption by the interstellar medium, making it a prime candidate for probing atmospheric escape from HD 60779 b. HD 60779 is also the third brightest host of a P _orb > 25 day sub-Neptune with a measured mass and radius, distinguishing it in terms of accessibility to spectroscopic characterization.