arXiv subjects

S. Benatti

Publications and source records attributed to S. Benatti.

At least 19 recordsLinked to original sources

arXiv2026

The GAPS Programme with HARPS-N at TNG LXXVII. Occurrence rates of small close-in planets in the presence of cold Jupiters

Context. The architecture of our Solar System, with inner small planets (ISPs) and outer giants, may or may not be common. Understanding whether a correlation exists between ISPs and outer cold giants is key to evaluating how common systems with a similar architecture to our own are. Aims. This study aims to build a large, homogeneous sample of systems hosting cold Jupiters (CJs, a > 1 au, msini > 0.1 M$_J$) detected via radial velocities (RVs), and to assess the presence of additional ISPs (P < 400 d, 3 < msini < 31.7 M$_{\oplus}$), studying the correlation between these two types of objects. Methods. We selected 137 stars known to host a CJ, including 23 which also harbor a hot Jupiter and were treated separately. Data from various instruments were compiled, including unpublished data gathered with HARPS-N within the GAPS program, and consistently fitted using PyORBIT. We derived RV detection maps and calculated occurrence rates for ISPs, cross-validating results with two independent codes. The sample was divided into subgroups to evaluate how system parameters influence planet occurrence. Results. We confirmed the 213 already known planets in the 137 systems and also identified six new candidates. We divided them, based on mass and period, into Neptunes (10 < m sin i < 31.7 M$_{\oplus}$) and Super-Earths (3 < m sin i < 10 M$_{\oplus}$), and into hot (1 < P < 10 d), warm (10 < P < 100 d), and cool (100 < P < 400 d). We found occurrences of 5%, 13%, and 12% for hot, warm, and cool Neptunes, respectively, and 11% and 16% for hot and warm Super-Earths, respectively. Systems with dynamically stable inner regions show higher rates of small planets. These findings are consistent with previous studies showing no strong correlation between ISPs and CJs at average stellar metallicity and mass, and suggest that HJs may be more commonly associated with external giants.

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arXiv2026

The 35-Myr old infant planet TOI-837 b has a mildly misaligned orbit

The measurement of the spin-orbit obliquity, that is, the angle between the orbital axis of a planet and the stellar spin axis, provides crucial insights into how planets form and migrate. Observations of young transiting planets, which have not yet experienced significant tidal alterations, offer a unique opportunity to study their original obliquity configuration. We observed the warm Saturn-sized TOI-837 b (member of the 35 Myr old open cluster IC 2602) in-transit using ESPRESSO at VLT, collecting high-precision radial velocities to measure the Rossiter-McLaughlin effect. We found a sky-projected obliquity of $\lambda = 341.1^{+2.3}_{-2.5}$ deg. Using our knowledge of the stellar rotation period ($3.00 \pm 0.02$ d), we estimated a true obliquity of $\psi = 25.9^{+7.5}_{-6.3}$ deg, which indicates prograde motion and suggests a mildly misaligned orbit. This places TOI-837 b as the first planet younger than 100 Myr with accessible $\psi$ incompatible with an aligned orbit. Together with the primordial circular orbit of TOI-837 b and the presence of a bound stellar companion, this mild misalignment favours the possibility of a primordial obliquity excitation (secular torque on the protoplanetary disc) followed by disc-driven migration, rather than high-eccentricity migration after formation.

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arXiv2026

Ariel stellar characterisation IV. Fundamental parameters of 18 hot stars in the Ariel mission candidate sample

The characterisation of exoplanetary systems depends on the accurate determination of host star parameters. The Ariel mission will probe the atmospheres of a statistically significant sample of exoplanets, and so requires a precise characterisation of the stellar properties well before its launch in 2029. The homogeneous determination of stellar parameters for Ariel will enable both the optimisation of the final target list and set roots for a reliable interpretation of the formation and evolution of planetary systems. Such a homogeneous characterisation has thus far only been carried out for the cool (\teff\ $\lesssim 7000\,$K) host stars among the Ariel target candidates. We present a uniform determination of fundamental stellar parameters for 18 hot stars in the Tier 1 candidate list of the Ariel mission candidate sample. We adopted an iterative spectro-trigonometric approach optimised for high-temperature stars. High-resolution spectra were analysed using the \textsc{zeeman} code with $\chi^2$ minimisation, combining model fits to metal and Balmer lines. Surface gravity was refined using photometry-based radii and masses from stellar evolutionary tracks. We derived effective temperatures, surface gravities, projected rotational velocities, microturbulent velocities, overall metallicities, iron abundances, stellar masses, and radii for our sample of $18$ hot stars. Our results were validated against a set of benchmark stars previously presented in the literature. The derived parameters provide an internally consistent basis for studying the link between stellar properties and planetary characteristics in intermediate-mass stars. Building on our previous work on FGK host stars, we show that correlations between stellar mass, metallicity, and planetary radii also extend to early-type stars, and stellar properties influence the architecture of multi-planet systems.

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arXiv2026

A tidally detached super Neptune on a strongly misaligned retrograde orbit

The obliquity between a planet's orbital axis and its host star's spin axis provides crucial insights into planetary formation and migration. Planets with scaled semi-major axes ($a/R_\star$) large enough to be unaffected by tidal alterations ("tidally detached"), offer a unique opportunity to study the original obliquity in which the system formed. We therefore observed TOI-1710 b ($a/R_\star \approx 36$) in-transit using HARPS-N + GIANO-B, collecting high-precision radial velocities to measure the Rossiter-McLaughlin (RM) effect. Spectral analysis of the H$\alpha$ and HeI triple lines was also pursued to evaluate atmospheric photoevaporation. Using our knowledge of the star rotation period ($21.5 \pm 0.2$ d), we estimated a true obliquity of $\psi = 149 ^{+11}_{-10}$ deg, which indicates a retrograde motion and places TOI-1710 b among the most misaligned systems -- and the only one known orbiting a cool star in retrograde motion. The strong misalignment favours a high-eccentricity migration (HEM) origin for this low-density super-Neptune planet in the savanna region, challenging previous findings that claimed a minor role of HEM in this period-radius(-density) domain. Moreover, the strong misalignment and lack of a detected close stellar companion suggests a purely planetary post-migration misalignment, likely due to planet-planet scattering followed by planet-planet Kozai-Lidov oscillations and tidal circularisation.

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arXiv2026

The GAPS Programme at TNG. LXXIII. Confirmation of the hot sub-Neptune TOI-4602 b (HD 25295 b), a key target for future atmospheric characterization

Precise mass and radius measurements of small, transitional exoplanets, such as super-Earths and sub-Neptunes, are essential to constrain their bulk density and formation history, serving as prerequisites for atmospheric characterization. The ArMS Large Programme, carried out within GAPS using the HARPS-N spectrograph at the Telescopio Nazionale Galileo, aims to confirm and characterize transitional planets in the radius valley through high-precision radial-velocity (RV) measurements. The ultimate goal is to identify ideal targets for atmospheric follow-up observations with next-generation facilities like the James Webb Space Telescope and the future ESA Ariel satellite. We present the first mass determination of a sub-Neptune planet using data entirely collected within the ArMS programme, focusing on the validated planet TOI-4602b. We monitored TOI-4602, which hosts a close-in validated sub-Neptune (P ~ 3.98 d) detected by the Transiting Exoplanet Survey Satellite (TESS), searching for planet-induced RV variations. We then performed a joint analysis of these RV measurements together with the TESS photometric data. We determined that TOI-4602b is a sub-Neptune with a radius of Rp = 2.5 Rearth and a mass of Mp = 5.5 Mearth. The resulting bulk density (rho_p = 2.1 ) and atmospheric evolution modelling suggest the planet is retaining a tenuous envelope while evolving toward a bare core, consistent with a position immediately above the radius valley. g cm^ -3 Given its bright (V = 8.4) and quiet host star and the high Transmission Spectroscopy Metric (TSM) value (140 +/- 54), TOI-4602,b is a prime target for atmospheric characterization. Simulated retrievals indicate that JWST and Ariel can effectively constrain its atmospheric composition, offering a unique window into the physical processes driving the sub-Neptune to super-Earth transition.

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arXiv2026

The PLATO field selection process III. Selection of the Prime Sample for the LOPS2 field

The PLanetary Transits and Oscillations of stars (PLATO) mission will begin its four-year nominal mission in early 2027 by monitoring its Long-duration Observation Phase field at South (LOPS2) for at least two years continuously. The primary aim of PLATO is a very ambitious and challenging one: the discovery of Earth-like planets in the habitable zone of nearby and bright solar analogues. To this purpose, the PLATO Mission Consortium, through its Ground-based Observing Program, will perform the follow-up needed to confirm part of the candidate planets photometrically detected by PLATO and measure their masses through radial velocity curves. For the LOPS2, the Ground-based Observing Program is committed (as part of the PLATO mission) to follow-up the candidate exoplanets discovered orbiting the 15,000 high-quality target subset of the PLATO Input Catalog (PIC) known as the Prime Sample. The Prime Sample will be made public nine months before launch in the context of the first Guest Observer call for proposals to be issued by the European Space Agency. Here, we present the quantitative metrics and thresholds defined to select and prioritize the Prime Sample. Our method is perfectly general and suitable to rank any list of stars surveyed for transiting planets. We also describe the astrophysical properties of the LOPS2 Prime Sample, both in a statistical sense and for some specific targets of interest.

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arXiv2026

The PLATO Input Catalogue of targets (tPIC) for the first Long Pointing Field

The ESA PLAnetary Transits and Oscillations of stars (PLATO) mission is designed to detect terrestrial planets in the habitable zones of solar-type stars. Owing to telemetry constraints, the selection of PLATO targets must be performed in advance. In this paper, we present the first public release of the PLATO Input Catalogue of targets (tPIC2.2), which provides the list of stars that will be observed during the PLATO first Long-duration Observation Phase field at South (LOPS2) as part of its core science program. We exploit astrometric and photometric data from Gaia Data Release 3 (DR3), together with three-dimensional maps of the local interstellar medium, to identify stars belonging to the PLATO stellar samples as from mission requirements. The tPIC comprises 217,741 stars, including 202,315 FGK dwarfs and subgiants, 15,037 M dwarfs and 789 known planet host stars. The median distances of the samples are 512 pc for FGK stars and 133 pc for M dwarfs. We estimate interstellar reddening for almost all targets and develop an algorithm to infer fundamental stellar parameters (effective temperature, radius, and mass) in an homogeneous way from astrometric and photometric observables. The tPIC fulfills all the science requirements of the PLATO mission. The tPIC also includes a list of stars that host known exoplanets (confirmed or still candidate), located within the LOPS2 field.

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arXiv2026

The GAPS Programme at the TNG: LXX. TOI-5734b: A hot sub-Neptune orbiting a relatively young K dwarf with an Earth-like density

Increasing interest in young exoplanets is leading to a growing effort to understand the formation and evolutionary processes responsible for their different architectures. One interesting target is TOI-5734, a relatively young K3-K4 dwarf star ($500_{-150}^{+300}$ Myr) showing a transiting candidate in photometric observations followed up with high-resolution spectroscopic data. Using Transiting Exoplanet Survey Satellite (TESS) photometry and High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) radial-velocity (RV) data, we aim to validate the presence of the companion TOI-5734b, measure its planetary mass, size, and its orbital parameters after having characterised its host star. We then aim to study its possible planetary composition and atmospheric evolution. By simultaneously modelling photometry and high-cadence RVs, we measured the radius, mass, and density of TOI-5734b precisely. In particular, we employed Gaussian processes (GPs) with a flexible kernel to discriminate between the stellar activity of the young host and planetary signals. We confirmed the planetary nature of TOI-5734b and measured its orbital period ($P_{\rm b}\sim6.18$ d), radius ($R_{\rm b} = 2.10^{+0.12}_{-0.12}$ $R_\oplus$), and mass ($M_{\rm b}=9.1^{+2.6}_{-2.6}$ $M_\oplus$). By measuring its density ($\rho_{\rm b}=0.98_{-0.30}^{+0.36}$ $\rho_\oplus$), we infer that TOI-5734b is close to having a rocky composition and an almost completely depleted primary envelope. Our results point toward the possibility of considering the target for atmospheric studies with present and future ground- and space-based facilities.

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arXiv2026

True Masses using RV data with Hipparcos and Gaia Astrometry

Long-period companions are detected and characterized thanks to long-baseline radial velocity surveys. Combining Doppler time-series with astrometry, and in particular with proper motion anomalies technique, it is possible to put strong constraints on their orbital inclination and true mass. This work aims to present a model that combines Hipparcos and Gaia astrometric data with radial velocity measurements to constrain the orbital inclinations and true masses of long-period companions. Additionally, we re-analyse a small sample of targets that have not yet been studied using this combined approach. This research leverages the simultaneous modelling of proper motion anomalies and radial velocities, in conjunction with an analysis of the sensitivity curve. This approach serves not only as a verification of the parameters but also as a means to acquire valuable insights into planetary systems. The new analyses reveal that some of the targets classified as brown dwarfs or small-mass stars have a planetary nature. HD 5388 b and HD 6718 b are likely planets. HD 141937 b is likely a planet, but the current dataset does not allow us to firmly constrain its true mass. HD 16760 b belongs to the brown dwarf regime and it has a probable second companion. 30 Ari B b falls within the stellar regime, but the presence of an additional stellar companion could compromise the reliability of the final results. For HD 148427 b, HD 96127 b and HIP 65891 b we determined a range for the orbital inclinations.

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arXiv2025

Selection and characterisation of the M-dwarf targets in the PLATO Input Catalogue

The ESA's PLAnetary Transits and Oscillations of Stars (PLATO) mission aims to detect planets orbiting around dwarfs and subgiant stars with spectral type F5 or later, including M-dwarfs. The PLATO Input Catalogue (PIC) contains all targets available for observation by the nominal science. The latest version, PIC2.1.0.1, focuses on the Southern PLATO field, named LOPS2, selected as the first long observation field, and includes the P4 sample, one of the four target samples outlined in the Science Requirement Document. P4 includes the M-dwarfs with magnitudes V < 16 located within LOPS2. A characterisation of the M-dwarfs in the PIC is essential for assessing their potentiality to host exoplanets, and eventually estimate the hosted planet(s) properties. The purpose of this paper is to describe how we selected the P4 M-dwarf targets, and obtained their fundamental parameters and properties. In this work, we introduce the P4 sample and detail the methodologies adopted for the measurement of their stellar parameters. Based on a statistical analysis of the P4 sample, we assess both the photometric and volume completeness, and classify the stellar populations according to their Galactic spatial-velocity components. The adopted stellar parameters are validated by comparison with independent methods from the literature used to estimate stellar radii. The P4 sample is compliant with the PLATO science requirements. Being magnitude limited, its volume completeness decreases going towards distances larger than 30 pc, where late-type targets are progressively less covered. The observed large spread in the colour-magnitude diagram is likely due to the combination of several effects such as metallicity, age, binarity and activity. The strategy we adopted for deriving stellar parameters provides results consistent with those obtained in the literature with different and independent methods.

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arXiv2025

Long-term X-ray variability of the multiple-planet host L 98-59: Hints of an activity cycle

High-energy irradiation in X-rays and UV (XUV) can transform the planetary atmospheres through photoevaporation and photochemistry. This is more crucial for M stars, whose habitable zones for Earth-like planets are located within a few percent of an AU. Transiting exoplanets around M dwarfs offer the opportunity to study their characteristics and habitability conditions. L 98-59 is an M3 dwarf hosting six Earth-like planets, with two of them in the habitable zone of the star. X-ray observations made in 2020 and 2021 detected significant flares above a quiescent luminosity of 4-10 x 10^26 erg/s. We present the results from two short XMM-Newton observations of L 98-59, which are part of a monitoring survey to detect long-term X-ray variability and activity cycles. In October 2024 the X-ray quiescent luminosity of the star was about 5.9 x 10^25 erg/s, and it was about 6.3 x 10^26 erg/s in February 2025. We speculate that in late 2024 the star had a minimum of activity; in 2021 the star was near a maximum of an activity cycle, and in 2025 it was at the middle of the cycle. We suggest a coarse estimate of the period of about 2 years and a peak-to-peak amplitude of about 10, which is the highest among the stars with a known X-ray cycle other than the Sun. We also infer that even the outer planet in the habitable zone, L 98-59f, is exposed to an X-ray dose between 100 and 1600 times the X-ray irradiation of the Earth in the XMM band.

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arXiv2025

A 34.6-day transiting sub-Neptune in the TOI-1422 planetary system

TOI-1422 is a G2 V star ($V = 10.6$ mag) known to host a warm Neptune-sized planet, TOI-1422 b, with a mass and radius of about $9M_{\oplus}$ and $4R_{\oplus}$, on a circular orbit with a period of $12.997$ days. An outer planetary candidate in this system had previously been suggested on the basis of a residual signal in the radial velocity (RV) data with a tentative period of $\sim$29 days, along with a possible single transit-like event, although it was not clear at the time whether the two signals belonged to the same companion. In this work, we confirm the presence of a second transiting planet, TOI-1422 c, a sub-Neptune ($R=2.61\pm0.14 R_{\oplus}$) that orbits with a longer period of 34.563 days. This confirmation is based on the detection of three TESS transits, two from newly available sectors, combined with new and archival RV measurements. The sub-Neptune ($\rho_{\rm c}=4.3^{+1.3}_{-1.0}$ g cm$^{-3}$) is more massive than the inner Neptune ($\rho_{\rm b}=0.93^{+0.21}_{-0.20}$ g cm$^{-3}$), having a mass of $M_{\rm c}=14\pm3 M_{\oplus}$, making TOI-1422 a rare anti-ordered system. Furthermore, we detect transit timing variations (TTVs) on the inner planet, with amplitudes of up to 5 hours, suggesting ongoing dynamical interactions. A dynamical analysis that combined TTVs and RVs indicates that planet c alone is unlikely to account for the full TTV amplitude observed on TOI-1422 b. We investigated whether an additional, as yet undetected companion could account for the observed signal, exploring a range of plausible orbital configurations and finding that a low-mass planet located between the two known orbits may be responsible.

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arXiv2025

The GAPS programme at TNG LXXI. A sub-Neptune suitable for atmospheric characterization in a multiplanet and mutually inclined system orbiting the bright K dwarf TOI-5789 (HIP 99452)

Sub-Neptunes with planetary radii of $R_{p} \simeq 2-4 R_{\oplus}$ are the most common planets around solar-type stars in short-period ($P<100$ d) orbits. It is still unclear, however, what their most likely composition is, that is whether they are predominantly gas dwarfs or water worlds. The sub-Neptunes orbiting bright host stars are very valuable because they are suitable for atmospheric characterization, which can break the well-known degeneracy in planet composition from the planet bulk density, when combined with a precise and accurate mass measurement. Here we report on the characterization of the sub-Neptune TOI-5789 c, which transits in front of the bright ($V=7.3$ mag and $K_{s}=5.35$ mag) and magnetically inactive K1V dwarf HIP 99452 every 12.93 days, thanks to TESS photometry and 141 high-precision radial velocities obtained with the HARPS-N spectrograph. We find that its radius, mass, and bulk density are $R_{c}=2.86^{+0.18}_{-0.15} R_\oplus$, $M_{c}=5.00 \pm 0.50 M_\oplus$, and $\rho_{c}=1.16 \pm 0.23$ g cm$^{-3}$, and we show that TOI-5789 c is a promising target for atmospheric characterization with both JWST and, in the future, Ariel. By analyzing the HARPS-N radial velocities with different tools, we also detected three additional non-transiting planets, namely TOI-5789 b, d, and e, with orbital periods and minimum masses of $P_{b}=2.76$ d, $M_{b}\sin{i}=2.12 \pm 0.28 M_\oplus$, $P_{d}=29.6$ d, $M_{d}\sin{i}=4.29 \pm 0.68 M_\oplus$, and $P_{e}=63.0$ d, $M_{e}\sin{i}=11.61 \pm 0.97 M_\oplus$. TOI-5789 is a mutually inclined system as the difference between the orbital inclinations of planets b and c must be higher than $\sim4$ deg. Nevertheless, from sensitivity studies based on both the HARPS-N and archival HIRES radial-velocity measurements, we can exclude that these relatively high mutual inclinations are due to the perturbation by an outer gaseous giant planet.

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arXiv2025

A comprehensive study on radial velocity signals using ESPRESSO: Pushing precision to the 10 cm/s level

We analyse ESPRESSO data for the stars HD10700, HD20794, HD102365, and HD304636 acquired via its Guaranteed Time Observations (GTO) programme. We characterise the stars' radial velocity (RV) signals down to a precision of 10 cm/s on timescales ranging from minutes to planetary periods falling within the host's habitable zone (HZ). We study the RV signature of pulsation, granulation, and stellar activity, inferring the potential presence of planets around these stars. Thus, we outline the population of planets that while undetectable remain compatible with the available data. A simple model of stellar pulsations successfully reproduced the intra-night RV scatter of HD10700 down to a few cm/s. For HD102365 and HD20794, an additional source of scatter at the level of several 10 cm/s remains necessary to explain the data. A kima analysis was used to evaluate the number of planets supported by the nightly averaged time series of each of HD10700, HD102365, and HD304636, under the assumption that a quasi-periodic Gaussian process (GP) regression is able to model the activity signal. While a frequency analysis of HD10700 RVs is able to identify a periodic signal at 20d, when it is modelled along with the activity signal the signal is formally non-significant. ESPRESSO data on their own do not provide conclusive evidence for the existence of planets around these three stars. ESPRESSO is shown to reach an on-sky RV precision of better than 10 cm/s on short timescales (<1h) and of 40 cm/s over 3.5 yr. A subdivision of the datasets showcases a precision reaching 20-30 cm/s over one year. These results impose stringent constraints on the impact of granulation mechanisms on RV. In spite of no detections, our analysis of HD10700 RVs demonstrates a sensitivity to planets with a mass of 1.7M$_{\oplus}$ for periods of up to 100 d, and a mass of 2-5M$_{\oplus}$ for the star's HZ. (abridged)

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arXiv2025

Ariel stellar characterisation III. Fast rotators and new FGK stars in the Ariel Mission Candidate Sample

The next mission dedicated to the study of planetary atmospheres is the Ariel space mission, planned for launch in 2029, which will observe a variety of planetary systems belonging to different classes around stars with spectral types from M to A. To optimise the scientific outcome of the mission, such stars need to be homogeneously characterised beforehand. In this work, we focus on a methodology based on spectral synthesis for the characterisation of FGK-type stars from the Ariel Tier 1 Mission Candidate Sample (MCS) which exhibit fast rotation. In addition, we analyse slow-rotating FGK-type stars, with either new observations or archival spectra available, consistently as in our previous work using the equivalent width (EW) analysis. To ensure consistency between our methods, we re-analysed a sample of FGK-type stars with the spectral synthesis method and compared it to our previous work. The results of our analysis show excellent agreement with the previous set of derived parameters. We also computed their orbital parameters establishing whether they belong to the Galactic thin or thick discs. With the current set of stellar parameters, we almost double the analysed hosts in the Ariel MCS to 353 stars in total. Using our homogeneous set of stellar parameters, we studied the correlations between stellar and planetary properties for the Ariel MCS analysed so far. We confirmed a close relationship between stellar mass (up to 1.8 solar masses) and giant planet radius, with more inflated planets at lower metallicity. We confirm that giant planets are more frequent around more metal-rich stars that belong to the thin disc, while lower-mass planets are also found in more metal-poor environments, and are more frequent than giant planets in the thick disc as also seen in other works in the literature.

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arXiv2025

Revisiting the multi-planetary system of the nearby star HD 20794: Confirmation of a low-mass planet in the habitable zone of a nearby G-dwarf

Close-by Earth analogs and super-Earths are of primary importance because they will be preferential targets for the next generation of direct imaging instruments. Bright and close-by G-to-M type stars are preferential targets in radial velocity surveys to find Earth analogs. We present an analysis of the RV data of the star HD 20794, a target whose planetary system has been extensively debated in the literature. The broad time span of the observations makes it possible to find planets with signal semi-amplitudes below 1 m/s in the habitable zone. We monitored the system with ESPRESSO. We joined ESPRESSO data with the HARPS data, including archival data and new measurements from a recent program. We applied the post-processing pipeline YARARA to HARPS data to correct systematics, improve the quality of RV measurements, and mitigate the impact of stellar activity. Results. We confirm the presence of three planets, with periods of 18.3142 +/- 0.0022 d, 89.68 +/- 0.10 d, and 647.6 +/- 2.6 d, along with masses of 2.15 +/- 0.17 MEarth, 2.98 +/- 0.29 MEarth, and 5.82 +/- 0.57 MEarth respectively. For the outer planet, we find an eccentricity of 0.45 +/- 0.10, whereas the inner planets are compatible with circular orbits. The latter is likely to be a rocky planet in the habitable zone of HD 20794. From the analysis of activity indicators, we find evidence of a magnetic cycle with a period around 3000 d, along with evidence pointing to a rotation period around 39 d. We have determined the presence of a system of three planets orbiting the solar-type star HD 20794. This star is bright (V=4.34 mag) and close (d = 6.04 pc), and HD 20794 d resides in the stellar habitable zone, making this system a high-priority target for future atmospheric characterization with direct imaging facilities.

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arXiv2025

The PLATO field selection process. II. Characterization of LOPS2, the first long-pointing field

PLAnetary Transits and Oscillations of stars (PLATO) is an ESA M-class mission to be launched by the end of 2026 to discover and characterize transiting planets around bright and nearby stars, and in particular habitable rocky planets hosted by solar-like stars. Over the mission lifetime, an average of 8% of the science data rate will be allocated to Guest Observer programs (GOs) selected by ESA through public calls, hence it is essential for the community to know in advance where the observing fields will be located. In a previous paper, we identified two preliminary long-pointing fields (LOPN1 and LOPS1) for PLATO, respectively in the northern and southern hemisphere. Here we present LOPS2, a slightly adjusted version of the southern field that has recently been selected by the PLATO Science Working Team as the first field to be observed by PLATO for at least two continuous years, following the scientific requirements. In this paper, we describe the astrophysical content of LOPS2 in detail, including known planetary systems, bright/variable/binary stars, clusters and synergies with other current and future facilities.

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arXiv2024

The GAPS Programme at TNG. LXV. Precise density measurement of TOI-1430 b, a young planet with an evaporating atmosphere

Small-sized exoplanets in tight orbits around young stars (10-1000 Myr) give us the opportunity to investigate the mechanisms that led to their formation, the evolution of their physical and orbital properties and, especially, of their atmospheres. Thanks to the all-sky survey carried out by TESS, many of these exoplanets have been discovered and have subsequently been characterized with dedicated follow-up observations. In the context of a collaboration among the GAPS, TKS and CPS teams, we measured with a high level of precision the mass and the radius of TOI-1430 b, a young (~700 Myr) exoplanet with an escaping He atmosphere orbiting the K-dwarf star HD 235088 (TOI-1430). By adopting appropriate stellar parameters, which were measured in this work, we were able to simultaneously model the signals due to strong stellar activity and the transiting planet TOI-1430 b in both photometric and spectroscopic series. This allowed us to measure the density of the planet with high precision, and reconstruct the evolution of its atmosphere. TOI-1430 is an active K-dwarf star born 700+/-150 Myr ago and rotates in ~12 d. It hosts a mini-Neptune whose orbital period is Pb=7.434133+/-0.000004 d. Thanks to long-term monitoring of this target performed with TESS, HARPS-N, HIRES, and APF, we estimated a radius Rb=1.98+/-0.07 $R_{\oplus}$, a mass Mb=4.2+/-0.8 $M_{\oplus}$, and thus a planetary density $\rho$b=0.5+/-0.1 $\rho_{\oplus}$. TOI-1430 b is hence a low-density mini-Neptune with an extended atmosphere, at the edge of the radius gap. Because this planet is known to have an evaporating atmosphere of He, we reconstructed its atmospheric history. Our analysis supports the scenario in which, shortly after its birth, TOI-1430 b may have been super-puffy, with a radius 5x-13x and a mass 1.5x-2x that of today; in ~200 Myr from now, TOI-1430 b should lose its envelope, showing its Earth-size core.

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