Luigi Mancini

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.

Neptune-sized exoplanets appear to be located in three distinct regions when plotted in the period-radius space: the desert, which is an ultra-close-in region nearest to the host star and is typically defined by orbital periods shorter than 3.2 days and is characterised by a scarcity of planets; the savanna, in which planets reside at a safer distance from their hosts and are found in moderate abundance; and an intermediate region called the ridge, which features a surprising statistical overdensity. The formation and evolution pathways by which a planet ends up in one of these three regions are still poorly understood. This makes any new planet that is discovered in these regions, especially in the desert, a key new laboratory. We report the confirmation of the TESS transiting-planet candidate orbiting the metal-rich F8IV-V subgiant star TOI-5646 ( V = 11.38 mag; T _eff = 6136 ± 51 K). The planetary nature of TOI-5646 b was confirmed by means of HARPS-N follow-up radial velocity measurements. We determined that the planet has an orbital period of 2.427702 ± 0.000025 days and an orbital eccentricity compatible with zero. With a mass of 45.9 ± 4.4 M _⊕ , a radius of 6.6 ± 0.3 R _⊕ , and an equilibrium temperature of 1935 ± 29 K, it is one of the hottest super-Neptune exoplanets ever discovered in the Neptune desert. Its density, 0.87 ± 0.15 g cm ⁻³ , is lower than that of most other desert dwellers, but still appears to follow the trend that the desert is populated by dense planets than those in the ridge and savanna. The metallicity of the parent star ([Fe/H] = 0.32 ± 0.06) follows the trend whereby the host stars of Neptune-sized exoplanets in the desert and the ridge are generally richer in metal than those in the savanna. The log g of the parent star, 4.09 ± 0.08, suggests that the host is an evolved star, making this a peculiar system: TOI-5646 is the largest star (∼1.8 R _⊙ ) ever discovered to host a Neptune-sized planet in the desert. Internal structure modelling revealed that TOI-5646 b is highly enriched in metals, with an inferred bulk metallicity between 0.7 and 0.95. Atmospheric evolution simulations indicate that the planet has undergone significant mass loss (6–16%) through intense XUV irradiation from its host star. These results indicate a peculiar formation history (potentially involving early protoplanetary disk dispersal), a planetary collision, or a late tidal destruction event, to explain its current state as a low-density survivor in the Neptune desert.

Among the different classes of exoplanets, ultra-hot Jupiters represent prime laboratories for atmospheric characterisation. With an equilibrium temperature of ~2300 K, KELT-20b/MASCARA-2b (HD 185603 b) is a well-studied ultra-hot Jupiter, for which several atomic species have already been detected in both transmission and emission spectroscopy. Nevertheless, important open questions remain regarding the completeness of the chemical inventory and the interpretation of spurious aliasing signals that may mimic genuine atmospheric signatures. In addition, asymmetries in the detected signals across transits can encode valuable information on the spatial structure and dynamics of the planetary atmosphere. In this work, we analyse seven transits of KELT-20b/MASCARA-2b observed with the high-resolution spectrograph HARPS-N at the Telescopio Nazionale Galileo. We apply the cross-correlation function technique to a large set of atomic and ionic species, accounting for aliasing effects that can lead to false detections. We confirm previous detections of H I , Na I , Mg I , Cr I , Fe I , and Fe II , and tentatively detect Cr II . We further report new detections of K I , Ca I , V I , Mn I , and Ba II , and a tentative detection of Pr I in the planetary atmosphere. By performing a phase-resolved analysis and splitting the transit into pre- and post-mid-transit phases, we investigate longitudinal variations in the detected signals. For several species, we observe a double-peaked structure in the K _p – V _sys maps, notably in Ca I , V I , Cr I , and Fe I , consistent with absorption arising from two distinct atmospheric limbs of the planet.

Context . Time-domain photometric monitoring is essential for characterizing cometary evolution, particularly for rare interstellar objects with limited observing opportunities. Aims . We aimed to characterize the pre-perihelion photometric behavior and dust activity of the interstellar comet 3I/ATLAS and to test the capability of the Black Hole Target and Observation Manager (BHTOM) platform and telescope network for coordinated high-cadence non-sidereal observations. Methods . We obtained 70 days of time-series photometry of 3I/ATLAS from 2025 July 4 to September 11 using 16 telescopes and 1554 images. The data were processed and calibrated with the BHTOM pipeline. High-cadence multiband imaging was used to measure the rotation period and color evolution, while the dust activity was quantified via Afρ measurements. Results . We present a pre-perihelion light curve of 3I/ATLAS from R _h = 3.18–2.19 au, which exhibited a steady brightening by ∼3 magnitudes with no evidence of anomalous behavior. We measured a rotation period of P _rot = 15.98 ± 0.08 h. The colors were statistically non-changing, with only a weak, non-significant tendency for 3I/ATLAS to become bluer at 3.5 > R _h > 2.2 au. The relative dust production increased from A (0°) fρ ∼600 to 1100 cm, and the upper limit on the dust mass-loss rate increased from ≤217 kg s ⁻¹ to ≤328 kg s ⁻¹ . We measured an activity index of n = −1.24 ± 0.02, which is consistent with a well-developed dust coma.

High-resolution imaging is widely used to constrain false positive scenarios in exoplanet validation, but it is a finite follow-up resource that reaches only a subset of candidates, and its population-level impact on validation outcomes has not been quantified through controlled removal experiments. Using an automated pipeline built on TRICERATOPS , we compute the false positive probability (FPP) of 443 TESS planet candidates. For the 264 planet candidates with high-resolution imaging observations, we compute FPP with and without the corresponding contrast curves, allowing us to quantify the impact of the additional data. We find that 72% of 68 contrast-curve-bearing validated planets would fail validation without their adopted contrast curves. The fraction requiring imaging decreases with increasing planet size, from 100% below 1.7 R _⊕ to 33% above 4 R _⊕ : within our sample and TRICERATOPS -based analysis, the availability of high-resolution imaging directly limits the yield of small-planet validation and the supply of validated targets for atmospheric characterization. Our analysis statistically validates 64 new TESS planets with sizes spanning 0.94 to 7.83 R _⊕ across hosts of spectral types: M through F. Four of these are highly amenable to JWST observations based on the transmission and emission spectroscopy metrics, and each achieves validation only with its imaging constraint.

The present-day architecture of planetary systems contains information about their formation and migration histories. The origin of hot Jupiters (HJs; P łesssim 10 d, R_ ̊m p > 8 R_⊕) has long been a matter of debate. While most of them are found to be `lonely', there is a rare population of HJs hosting small inner-orbit companions (eight known as of May 2026). Their peculiar architecture suggests a gentle disc-migration mechanism. In this study, we present the discovery and characterisation of the multi-planet system TOI-1533, comprising an inner sub-Neptune (TOI-1533 b, P_ ̊m orb = 3.63 d, R_ ̊m p = 3.15 R_⊕) and an outer hot giant planet (TOI-1533 c, P_ ̊m orb = 8.06 d, R_ ̊m p > 7.5 R_⊕) with substantial H/He by mass (ρ_ ̊m p < 0.48 g cm -3 $), both transiting an active K-dwarf star (T_ ̊m eff ≈ 5130 K; V (mag) ≈ 11). Our joint modelling of stellar activity and planetary signals from radial velocities (HARPS-N) and transits (TESS) allowed us to detect the planetary Keplerian signals (approximately 10 σ) and isolate the stellar modulation. The inclusion of simultaneous photometry in the multi-dimensional Gaussian processes formalism was a fundamental addition to the spectroscopic activity indicators, enabling the disentanglement of stellar activity from planetary signals. The mass ratio of the two confirmed planets (M_ ̊m b / M_ ̊m c about 0.8), together with the super-Neptune mass of the large outer companion ($M_ ̊m c ≈ 40 M_⊕), makes this system unusual compared to the other known HJs with low-mass inner companions.

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.

Hot Neptunes are close-in exoplanets that occupy a sparsely populated region of parameter space known as the hot Neptune desert. Their presence in this extreme environment is puzzling as it implies a complex history involving intense stellar radiation, atmospheric loss, and unique migration patterns that differ from more conventional Neptunes at larger orbital periods. We are running an observational programme aimed at enlarging the number of close-in Neptune-sized planets, with well-measured physical and orbital parameters. It contributes to the compilation of a statistically significant sample that will aid in clarifying the formation and migration pathways characterising this class of exoplanets. We used currently available TESS photometry, along with new (HARPS-N) and archival (HIRES) high-precision radial-velocity measurements, to review the main properties of the planetary systems TOI-1272 and TOI-1694 by means of joint-fit analyses. In the case of TOI-1272, this included Gaussian-process regressions for carefully modelling stellar activity. Our final estimates of the parameters of the two systems are consistent with previous measurements but have smaller uncertainties. We identified the radial-velocity variation of TOI-1272 found in the HIRES data as stellar activity, rather than planetary in nature and, therefore, we rejected the non-transiting planet TOI-1272,c. This opens up the possibility that TOI-1272,b's eccentricity is the result of high-eccentricity migration. The larger store of data at our disposal also allowed us to point out that both TOI-1694,b and TOI-1694,c move on slightly eccentric orbits. The current orbital architecture of TOI-1694 suggests a history of migration driven by both disc and dynamical interactions.

In transiting planetary systems, in which planetary sizes are accurately determined from transit observations, the presence of transit-timing variations¹ (TTVs), especially when combined with radial velocity (RV) data, provides powerful constraints on masses and orbital eccentricities. Together, these measurements offer crucial insights into system architecture, formation mechanisms and dynamical evolution. We present long-term RV and transit/TTV monitoring of the relatively young star (age approximately 1 Gyr) TOI-201, revealing an exceptional multi-planet system composed of a hot super-Earth (SE) size planet transiting every 5.8 days, a warm Jupiter (WJ) on a 53-day orbit and an eccentric (e = 0.62) low-mass brown dwarf (BD) on an approximately 8-year orbit, with an estimated mass M_BD of about 16 Jupiter masses. The BD is the longest-period transiting substellar object ever characterized by means of RVs and the only one known to be coplanar with inner planets. The architecture of this system suggests that the SE was formed isolated and in the innermost region of the gaseous disk. On the other hand, the orbital configuration of the outer companions suggests a nearly in situ formation of both objects, with the WJ forming in a dense inner disk. Alternatively, the BD might have formed farther out and migrated inward, while increasing its eccentricity owing to interactions with the disk.