Matteo Brogi

Aims . We aim to constrain the dynamical masses of the four confirmed transiting planets orbiting the infant (20 ± 10 Myr) star V1298 Tau (orbital periods P _b ∼ 24.1 d, P _c ∼ 8.2 d, P _d ∼ 12.4 d, and P _e ∼ 48.7 d), through a new analysis of a homogeneous radial-velocity dataset. This system is a key benchmark for testing formation and early-stage evolutionary models of planets. Methods . We analysed more than 380 high-resolution spectra collected with the HARPS-N spectrograph over a time span of 4.5 yr. To account for dominant stellar activity and transit-timing-derived planet–planet interactions, we analysed radial velocities extracted using two different approaches and combined N -body simulations with multi-dimensional Gaussian-process regression. We tested a set of spectroscopic and photometric activity diagnostics to mitigate the variability due to the stellar magnetic activity in the radial-velocity time series. Results . The mass determinations are sensitive to the choice of the radial-velocity extraction method and activity diagnostics. For some specific models, we measured masses with a significance of 3.5–4 σ for planets b (0.52 _−0.14 ^+0.12 , 0.65 _−0.18 ^+0.21 , 0.67 _−0.19 ^+0.16 , and 0.78 _−0.20 ^+0.19 M _Jup ) and e (0.40 _−0.13 ^+0.14 , 0.66 _−0.18 ^+0.17 , and 0.71 _−0.22 ^+0.18 M _Jup ). These values are compatible with masses of giant planets and are notably higher than those recently derived from transit timing variations alone, which indicate that these are low-density ‘super-puffy’ planets. Injection-and-recovery simulations moderately support this conclusion for planet b. For planets c and d, we primarily provide updated upper mass limits. Conclusions . Our analysis represents an exploratory study to address the complex issue of mass measurement in a multi-planetary system characterised by high levels of stellar activity. While firm conclusions cannot be drawn for V1298 Tau, in a few cases our results leave open the possibility that planet b in particular is a massive giant rather than a sub-Neptune progenitor. This dichotomy may be solved by combining radial velocities and transit time variations in a more complex photo-dynamical modelling, with a larger sample of transits than currently available.

Hot and ultra-hot Jupiters offer a unique laboratory for studying atmospheric chemistry at the population level using ground-based high-resolution spectroscopy. Iron (Fe) and titanium (Ti) are key tracers of thermal and chemical structures, yet they exhibit markedly different observational trends across the population. We present a homogeneous re-analysis of high-resolution transmission spectra for ten hot and ultra-hot Jupiters observed with ESPRESSO on ESO’s Very Large Telescope and MAROON-X on Gemini-North. We searched for neutral Fe and Ti absorption and performed injection–recovery tests using forward models spanning a range of Ti-depletion levels and temperature–pressure profiles. To enable direct comparison across planets observed with different instruments and signal-to-noise ratios, we introduced the relative cross-correlation metric, Δ _Ti-Fe . We detect Fe in seven planets and Ti in four planets at significances above 5 σ . Across the population, Δ _Ti-Fe decreases sharply towards lower equilibrium temperatures. Under the assumption of equal Ti depletion across planets, isothermal models fail to reproduce this trend, instead requiring a temperature-dependent depletion of Ti that increases towards cooler planets, consistent with cold-trapping processes in cooler atmospheres. Models with inverted temperature–pressure profiles naturally reproduce the decline without invoking such temperature-dependent depletion. In these atmospheres, Ti is converted into TiO in deeper, cooler layers and subsequently removed from the gas phase through condensation into Ti-bearing species, leading to a strong suppression of the observable atomic Ti signal while Fe remains largely atomic. Nevertheless, even in these gradient models, an additional overall depletion of Ti relative to Fe is required to match the hottest planets. Our results demonstrate that the observable refractory chemistry is governed by the interplay of molecular partitioning, ionisation, condensation, and cold-trapping processes, as well as the vertical structure of ultra-hot Jupiter atmospheres. Although these results reveal clear population-level trends, additional observations will be necessary to distinguish between temperature-dependent cold-trapping and overall depletion scenarios. Expanding homogeneous high-resolution surveys to larger and more diverse samples, targeting both emission and transmission observations, will refine these constraints and provide critical insights into the chemistry of strongly irradiated giant planets.

The astrometric measurements provided by the Gaia space mission represent a key advancement in the search for and characterisation of exoplanets, helping in particular to solve the mass degeneracy intrinsic to the radial velocity (RV) method. The fact that a fraction of astrophysical false positives contaminates the current catalogue of astrometric candidate solutions requires an RV follow-up to validate and confirm such candidates. Within the Global Architecture of Planetary Systems (GAPS) programme, we observed a selected sample of 14 stars with Gaia astrometric solutions compatible with the presence of a sub-stellar companion. The immediate aim of this survey is to identify astrophysical false positives and provide the first RV validation and confirmation of the remaining candidates. We analysed data collected with the HARPS-N spectrograph to identify stellar binary systems from the spectral cross correlation function profiles. The remaining astrometric candidates were characterised via Markov chain Monte Carlo analysis searching for the best-fit RV solution. Among the stars in our sample with astrometric candidate solutions, we identify six as originating from close binary companions mimicking the astrometric motion of distant sub-stellar companions, from which we can estimate an updated value of 43_ -11 ^ +13 % for the binary contamination fraction in the Gaia DR3 catalogue of astrometric candidates. We validate and confirm the remaining eight solutions, corresponding to giant and brown dwarf companions with minimum masses between 8 and 62 M_ Jup and semi-major axes between 0.76 and 1.42 au, providing the first RV characterisation for six of these candidates and updated orbital solutions for two previously confirmed ones.

Ultrahot Jupiters (UHJs; T _eq ≳ 2000 K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) elements in planetary atmospheres, providing a powerful diagnostic of planet formation and atmospheric processing. We present a comprehensive high-resolution cross-correlation spectroscopy analysis of the UHJ MASCARA-1 b ( T _eq ≈ 2600 K) using the IGRINS and IGRINS-2 spectrographs. We detect robust (signal-to-noise ratio > 4) signals from H ₂ O, CO, OH, Fe i , Mg i , Ca i , and Ti i , marking the most complete atmospheric inventory of MASCARA-1 b to date. Using a chemically consistent atmospheric inference framework, we constrain elemental abundances to a typical precision of ≈0.2 dex, retrieving a solar atmospheric metallicity ([M/H] _⊙ = 0.0 7 − 0.13 + 0.17 ≈1.2 × solar), a C/O ratio (C/O = 0.6 5 − 0.08 + 0.08 ) consistent with solar value (C/O = 0.59), an enhanced refractory abundance ([ R /H] _⊙ = 0.4 0 − 0.17 + 0.23 ≈ 2.5 × solar; ≈3.8 × stellar), and a moderately supersolar refractory-to-volatile ratio ([ R / V ] _⊙ = 0.3 6 − 0.09 + 0.11 ≈ 2.3× solar). Comparison with formation models suggests that MASCARA-1 b most likely accreted material between the soot–H ₂ O or H ₂ O–CO snowlines (at 68% confidence). We additionally find stellar values for atmospheric Ti/Fe and Ca/Fe ratios (at 68% confidence). The Mg/Fe is also found to be consistent with stellar value at 95% confidence. Therefore, we do not find strong indication of nightside cold trapping in MASCARA-1 b. As homogeneous refractory-to-volatile measurements expand across the UHJ population, particularly with upcoming Extremely Large Telescopes, these diagnostics will enable statistically robust tests of emerging trends in giant planet formation and atmospheric evolution.

Context . The transition regime between giant planets (GPs) and brown dwarfs (BDs) is still an open subject of study in exoplanetary science. A complete understanding of the population of long-period GPs and BDs would be pivotal for improving our knowledge of this topic, but the number of such objects with precisely measured orbital and physical parameters remains small. Moreover, their dynamical influence on smaller companions in inner orbits is still unclear. Aims . Within the framework of the Global Architecture of Planetary Systems collaboration (GAPS), we aim to confirm and characterise sub-stellar companion candidates from Gaia DR3, and to study the potential presence of additional lower mass planets in their systems. Methods . We present the results of an intensive high-precision radial velocity (RV) monitoring of HD 128717, which hosts the astrometric candidate Gaia-ASOI-009. We used the HARPS-N spectrograph at Telescopio Nazionale Galileo (TNG) to collect a high- cadence RV time series of the target. We used Markov chain Monte Carlo (MCMC) analyses to refine the Gaia DR3 orbital solution of the companion and, finally, performed a combined model of RV and proper motion anomaly (PMa) to derive the complete 3D orbit of the companion. We also ran a suite of numerical simulations to confirm our results. Results . We confirmed the sub-stellar nature of Gaia-ASOI-009 (i.e. Gaia-6 B). From the combined RV+PMa fit, we confirm that it is a high-eccentricity low-mass BD with P _B = 9.37 _−0.05 ^+0.06 , M _B = 19.8 ± 0.5 M _J , and e _B = 0.85, i _B = 130°. The derived orbital solution differs significantly from the one published in Gaia DR3. Through a series of dedicated simulations, we demonstrated that this discrepancy arises from a degeneracy in the Gaia DR3 astrometric solution. Specifically, the combination of Gaia-6 B long orbital period and high eccentricity, both poorly constrained by the limited time span of DR3, led to an incorrect solution characterised by a shorter period and lower eccentricity. Finally, we find no evidence of other companions in the system (in the inner or the outer regions). Thus, the origin of the high-eccentricity of Gaia-6 B remains unclear.

Context . The structure and evolution of close-in exoplanets are shaped by atmospheric loss and migration processes, which give rise to key population features such as the hot Neptune desert, ridge, and savanna – regions of the period-radius space whose boundaries offer critical insights into planetary formation and survival. Aims . As part of the KESPRINT collaboration, we selected the TESS transiting planet candidate TOI-3862.01 for radial velocity follow-up to confirm its planetary nature and characterize its mass and bulk properties. This planet candidate is of particular interest due to its position in the middle of the hot Neptune desert, making it a valuable probe for testing theories of planet migration and atmospheric loss. Methods . We confirmed the planetary nature and determined the mass of TOI-3862.01 (hereinafter TOI-3862 b) by performing a joint fit with both transit and radial velocity data, precisely characterizing the bulk properties of this planet. Results . TOI-3862b is a super-Neptune on a 1.56-day orbit around a Sun-like star with an effective temperature of 5300±50 K. It has a mass of 53.7 _−2.9 ^+2.8 M _⊕ and a radius of 5.53 ± 0.18 R _⊕ , corresponding to a density of 1.7±0.2 g/cm ³ . This places it among the rare population of hot and dense super-Neptune desert planets. Conclusions . TOI-3862b, residing deep in the hot Neptune desert, represents a rare occurrence in an otherwise sparsely populated region, offering a valuable opportunity to probe the processes that may allow planets to survive in such environments.

TOI-282 is a bright (V = 9.38) F8 main-sequence star known to host three transiting long-period ( P _b = 22.9 d, P _c = 56.0 d, and P _d = 84.3 d) small ( R _p ≈ 2–4 R _⊕ ) planets. The orbital period ratio of the two outermost planets, namely TOI-282 c and d, is close to the 3:2 commensurability, suggesting that the planets might be trapped in a mean motion resonance. We combined space-borne photometry from the TESS telescope with high-precision HARPS and ESPRESSO Doppler measurements to refine orbital parameters, measure the planetary masses, and investigate the architecture and evolution of the system. We performed a Markov chain Monte Carlo joint analysis of the transit light curves and radial velocity time series, and carried out a dynamical analysis to model transit timing variations and Doppler measurements along with N -body integration. In agreement with previous results, we found that TOI-282 b, c, and d have radii of R _b = 2.69 ± 0.23 R _⊕ , R _c = 4.13 _−0.14 ^+0.16 R _⊕ , and R _d = 3.11 ± 0.15 R _⊕ , respectively. We measured planetary masses of M _b = 6.2 ± 1.6 M _⊕ , M _c = 9.2 ± 2.0 M _⊕ , and M _d = 5.8 _−1.1 ^+0.9 M _⊕ , which imply mean densities of ρ _b = 1.8 _−0.6 ^+0.7 g cm ⁻³ , ρ _c = 0.7 ± 0.2 g cm ⁻³ , and ρ _d = 1.1 _{−0.2 +0.3} g cm ⁻³ , respectively. The three planets may be water worlds, making TOI-282 an interesting system for future atmospheric follow-up observations with JWST and ELT.