arXiv subjects

V. D'Orazi

Publications and source records attributed to V. D'Orazi.

At least 19 recordsLinked to original sources

arXiv2026

The Hot Neptune Initiative (HONEI) III. An ultra-hot super Neptune orbiting the metal-rich subgiant star TOI-5646: the largest host for a desert dweller

We report the confirmation of the TESS transiting-planet candidate orbiting the metal-rich F8\,IV-V subgiant star TOI-5646 (V=11.38 mag; T=6136 K). The planetary nature of TOI-5646b was confirmed by means of HARPS-N follow-up radial velocity measurements. We determined that the planet has an orbital period of 2.4277 days and an orbital eccentricity compatible with zero. With a mass of 45.9 Earth masses, a radius of 6.6 Earth radii, and an equilibrium temperature of 1935 K, it is one of the hottest super-Neptune exoplanets ever discovered in the Neptune desert. Its density, 0.87 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) 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) suggests that the host is an evolved star, making this a peculiar system: TOI-5646 is the largest star (1.8 Solar radii) ever discovered to host a Neptune-sized planet in the desert. Internal structure modelling revealed that TOI-5646b 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.

astro-ph.EP↗

arXiv2026

Radial abundance gradients of 18 elements in Galactic open clusters from infrared MWM spectra A detailed analysis of 655 giants in 133 clusters

Open clusters are powerful tools for studying the Milky Way. While large spectroscopic surveys now provide spectra for many cluster members, automated pipelines and heterogeneous membership selections can introduce systematics and inflate apparent cluster scatter. Therefore, a homogeneous re-analysis with careful membership control and an explicit treatment of departures from Local Thermodynamic Equilibrium is valuable for establishing robust abundance gradients. The aim is to derive precise Galactic radial abundance gradients for multiple elements using open cluster giants, and to investigate how these gradients depend on cluster age. We re-analysed high-resolution infrared APOGEE Milky Way Mapper spectra from DR19 of the Sloan Digital Sky Survey for 655 open cluster members selected from Gaia data that satisfied strict quality cuts on signal-to-noise ratio. Stellar parameters and 18 elemental abundances were obtained using spectrum fitting with the Python version of Spectroscopy Made Easy, applying Non-Local Thermodynamic Equilibrium corrections for several key atomic species. Further quality control of the results was made by visual inspection of all fitted synthetic spectra. The metallicity of the clusters decreases with Galactocentric radius, following a global slope close to -0.06 dex/kpc. Beyond 10-11 kpc, there is modest flattening. In addition to the elements analysed in the \cite{otto2026} study, we derive open-cluster gradients for V, Cu, Zn and Yb using APOGEE spectra.

astro-ph.GA↗

arXiv2026

On the use of field RR Lyrae as Galactic probes:. IX. Radial velocities

We present the largest and most homogeneous catalog of radial velocity (RV) measurements for field RR Lyrae (RRL) variables, based on both proprietary and publicly available spectroscopic data. The sample includes 17,563 RRLs pulsating in the fundamental mode (12,353 RRab), in the first overtone (5,011 RRc), and in double-mode (199 RRd). The RV curve (RVC) templates for metallic and Balmer lines were used to derive RV amplitudes and $V_γ$ velocities, defined as the RV of the stellar barycenter with respect to the Sun. The typical accuracy across the catalog is on average 3.8 km s$^{-1}$ for well-sampled RVCs, 6.5 km s$^{-1}$ for RVCs with 3-7 phase points and 11.3 km s$^{-1}$ for RVCs with fewer than three phase points. The use of different spectroscopic diagnostics and RVC templates provides, within the errors, very similar $V_γ$ velocities. We found that the metallicity dependence of RV amplitudes is vanishing for metallic lines, but becomes increasingly significant for H$γ$ and H$δ$. Moreover, the scaling relations between photometric (V, $G_{BP}$, G, $G_{RP}$) and RV amplitudes are linear for RRc and nonlinear for RRab variables, independently of the adopted diagnostic. This circumstantial evidence indicates that convection affects more luminosity than RV amplitudes when moving from the blue (hot) to the red (cool) edge of the instability strip. The spectroscopic Bailey diagram (RV amplitude versus period) shows a smooth transition and a reduced spread at a fixed period, when moving from metal-poor to metal-rich RRLs. Finally, we also found evidence that the metallicity distribution function of Blazhko RRLs is skewed toward the metal-intermediate and metal-rich regimes.

astro-ph.SR↗

arXiv2026

SHARP -- A spectrograph proposal to fully exploit ELT capabilities and look beyond JWST

The Extremely Large Telescopes (ELTs), with their large apertures and cutting-edge Multi-Conjugate Adaptive Optics (MCAO) systems, promise to deliver data that is both sharper and deeper than even the James Webb Space Telescope (JWST) across large fields. SHARP is a concept study for a near-IR (0.95-2.45 $μ$m) spectrograph specifically designed to fully exploit the collecting area and angular resolution capabilities of the upcoming ESO's ELT. The instrument concept is driven by the goal of tackling the most important questions in astrophysics and cosmology, from exploring primordial galaxies to studying the formation of young stellar object and planetary systems in the nearby dust-enshrouded regions, bridging the gap between the local and the distant Universe. This requires versatility to accommodate diverse observational needs. SHARP is composed of two main units: NEXUS, a Multi-Object Spectrograph (MOS) optimized for detecting the faintest sources, and VESPER, a multi-object Integral Field Unit (multi-IFU) designed for brighter ones. This article provides an overview of the scientific design drivers, the solutions developed to meet them, and the resulting optical design that achieves the required performance.

astro-ph.IM↗

arXiv2026

The GAPS programme at TNG LXXV. Validating and confirming Gaia substellar astrometric candidates with HARPS-N

The astrometric measurements provided by the Gaia space mission represent a key advancement in the search and characterization 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 catalog of astrometric candidate solutions requires an RV follow-up to validate and confirm such candidates. Within the GAPS programme, we have observed a selected sample of 14 stars having Gaia astrometric solutions compatible with the presence of a substellar 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 characterized 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 6 as originating from close binary companions mimicking the astrometric motion of distant substellar companions, from which we can estimate an updated value of $43_{-11}^{+13}\%$ for the binary contamination fraction in the Gaia DR3 catalog of astrometric candidates. We validate and confirm the remaining 8 solutions, corresponding to giant and brown dwarf companions with minimum masses between 8 and 62 $M_{\rm Jup}$ and semimajor axes between 0.76 and 1.42 au, providing the first RV characterization for 6 of these candidates and updated orbital solutions for 2 previously confirmed ones.

astro-ph.EP↗

arXiv2026

The SPHERE infrared survey for exoplanets (SHINE) V. Full sample characterization

Unbiased surveys of large stellar samples are the prime means through which the prevalence of exoplanets can be derived, and crucial constraints to planet formation models can be set. Direct imaging (DI) is ideally positioned to probe the outer regions (5-300au) of planetary systems, providing complementary information to techniques such as transits and radial velocities. We present the full sample of the SpHere INfrared survey for Exoplanets (SHINE), the second largest DI campaign to date. SHINE observed 460 stars between 2015 and 2023 thanks to the guaranteed time observations (GTO) allocated by ESO to the SPHERE consortium at VLT. The goal of this paper is to homogeneously derive the stellar properties of the targets and to define a subsample of young single hosts to be used as a starting point for the final statistical analysis of the survey. Stellar ages were determined based on kinematic indicators (such as the membership to young moving groups), age diagnostics (lithium abundance, rotation, activity), and isochrone fitting. A thorough vetting for binarity was undertaken combining astrometric, spectroscopic, and imaging data. A subsample of 333 stars, covering a large extent of stellar ages and masses, was constructed. Selection criteria, global features, as well as the properties of individual stars are reported and discussed.

astro-ph.EP↗

arXiv2026

On the Use of Field RR Lyrae as Galactic Probes -- VIII. Early Formation of the Galactic Spheroid

We introduce a new photometric catalog of RR Lyrae variables (RRLs, $\sim$300,000) mainly based on data available in public datasets. We also present the largest and most homogeneous spectroscopic dataset of RRLs and Blue Horizontal Branch [BHB] stars ever collected. This includes radial velocity measurements ($\sim$16,000) and iron abundances ($Δ$S method for 8,140 RRLs, plus 547 from literature). Elemental abundances based on high-resolution spectra are provided for 487 RRLs and 64 BHB stars. We identified candidate RRLs associated to the main Galactic components and their iron distribution function (IDF) becomes more metal-rich when moving from the Halo ([Fe/H]=-1.56) to the Thick (TCD; [Fe/H]=-1.47) and Thin (TND; [Fe/H]=-0.73) disk. Furthermore, Halo RRLs and RRLs in retrograde orbits are $α$-enhanced ([$α$/Fe]=0.27, $σ$=0.18), while TCD RRLs are either $α$-enhanced ([Fe/H]$\le$-1.0) or $α$-poor ([Fe/H]$>$-1.0), and TND RRLs are mainly $α$-poor ([$α$/Fe]=-0.01, $σ$=0.20). We also identified RRLs associated to the main stellar streams (Gaia-Sausage-Enceladus [GSE]; Sequoia, Helmi, Sagittarius) and we found that their IDFs are quite similar to Halo RRLs. However, GSE RRLs lack the metal-poor/metal-rich tails and their $α$-element distribution is quite compact. The iron radial gradient in Galactocentric distance for TND, TCD and Halo RRLs is negative and it decreases from -0.026, to -0.010, and to -0.002 dex/kpc. The iron radial gradient based on dry Halo (Halo without substructures) RRLs is, within the errors, equal to the global Halo. We also found a strong similarity between iron and [$α$/Fe] radial gradients of Milky Way RRLs and M31 globular clusters throughout the full range of galactocentric distances covered by the two samples.

astro-ph.GA↗

arXiv2025

The GAPS Programme at TNG LXVIII. Characterization of the outer substellar companion around HD 72659 with a multi-technique approach

Before discovering the first exoplanets, the Radial Velocity (RV) method had been used for decades to discover binary stars. Despite significant advancements in this technique, it is limited by the intrinsic mass-inclination degeneracy that can be broken when combining RVs with astrometry, which allows us to determine the orbital inclination, or direct imaging, from which we can estimate the true mass of the target. HD 72659 is a solar analog known to host a gas giant on a $\sim 10$-yr orbit and a massive outer companion. This work aims to confirm HD 72659 c, which was recently announced using data from HIRES and HARPS spectrographs in combination with Gaia's astrometric data. We monitored HD 72659 with HARPS-N in the framework of the GAPS project since 2012. We now combined our 91 spectra with literature data and Gaia DR3 high-precision astrometry to constrain the mass and the orbit of this object ($M_{\rm c} \sim 19$ $M_{\rm J}$, $a \sim 21$ au) that falls in the Brown Dwarf desert. Moreover, we analyzed our high-resolution imaging observation taken with SPHERE, but since the target was not detected, we could only derive upper limits on its mass. We characterize the orbital parameters of HD 72659 c, confirming the literature mass of this object but finding a period twice as high as previously reported, and we also refine the parameters of planet b with reduced uncertainties compared to previous works. Finally, we analyze and discuss the dynamic configuration of this system, finding that the Kozai-Lidov mechanism may be at work.

astro-ph.EP↗

arXiv2025

The Hot-Neptune Initiative (HONEI) I. Two hot sub-Neptunes on a close-in, eccentric orbit (TOI-5800 b) and a farther-out, circular orbit (TOI-5817 b)

Neptune-sized exoplanets are key targets for atmospheric studies, yet their formation and evolution remain poorly understood due to their diverse characteristics and limited sample size. The so-called "Neptune desert", a region of parameter space with a dearth of short-period sub- to super-Neptunes, is a critical testbed for theories of atmospheric escape and migration. The HONEI program aims to confirm and characterize the best Neptune-sized candidates for composition, atmospheric and population studies. By measuring planetary masses with high precision, we want to provide the community with optimal targets whose atmosphere can be effectively explored with the JWST or by ground-based high-resolution spectroscopy. For this purpose, we started a radial velocity follow-up campaign, using the twin high-precision spectrographs HARPS and HARPS-N, to measure the masses of TESS Neptune-sized candidates and confirm their planetary nature. In this first paper of the series, we confirm the planetary nature of two candidates: TOI-5800b and TOI-5817b. TOI-5800b is a hot sub-Neptune ($R_p=2.44\pm0.29$ $R_\oplus$, $M_p=9.4\pm1.8$ $M_\oplus$, $T_{eq} = 1108\pm20$ K) located at the lower edges of the Neptune desert ($P=2.628$ days) and is the most eccentric planet ($e\sim0.3$) ever found within $P<3$ d. TOI-5800b is expected to be still in the tidal migration phase with its parent star, a K3 V dwarf ($V=9.6$ mag), although its eccentricity could arise from interactions with another object in the system. Having a high-transmission spectroscopy metric ($TSM\sim103$), it represents a prime target for future atmospheric characterization. TOI-5817b is a relatively hot sub-Neptune ($R_p=3.08\pm0.14$ $R_\oplus$, $M_p=10.3\pm1.4$ $M_\oplus$, $T_{eq}=950\pm21$ K) located in the Neptune savanna ($P=15.610$ d) [...]

astro-ph.EP↗

arXiv2025

Stellar Population Astrophysics (SPA) with the TNG: NLTE atmospheric parameters and abundances of giant stars in 33 Open Clusters

Open clusters serve as important tools for accurately studying the chemical evolution of the Milky Way. By combining precise chemical data from high-resolution spectra with information on their distances and ages, we can effectively uncover the processes that have shaped our Galaxy. This study aims to derive NLTE atmospheric parameters and chemical abundances for approximately one hundred giant stars across 33 open clusters with near-solar metallicity. The clusters span a wide range of ages, enabling an assessment of the presence and extent of any age-related abundance gradients. In the Stellar Population Astrophysics (SPA) project, we acquired new high-resolution spectra of open clusters using the HARPS-N echelle spectrograph at the Telescopio Nazionale Galileo. We chemically characterized nine open clusters for the first time and reanalyzed previously studied SPA clusters, resulting in a consistent and homogeneous sample. We determined NLTE atmospheric parameters using the equivalent width method and derived NLTE chemical abundances through spectral synthesis for various elements, including alpha elements (Mg, Si, and Ti), light odd-Z elements (Na, Al), iron-peak elements (Mn, Co, and Ni), and neutron-capture elements (Sr, Y, and Eu). Our findings are compared with the existing literature, revealing good agreement. We examine the trends of [X/Fe] versus age, confirming previous observations and the enrichment patterns predicted by nucleosynthesis processes. Positive correlations with age are present for Mg, Si, Ti, Al, Mn, Co, Ni, and Sr, while Na and Y and Eu show a negative trend. This study emphasizes the significance of NLTE corrections and reinforces the utility of open clusters as tracers of Galactic chemical evolution. Furthermore, we provide a benchmark sample of NLTE abundances for upcoming open cluster surveys within large-scale projects such as 4MOST and WEAVE.

astro-ph.SR↗

arXiv2025

Protoplanetary disk insights from the first ERIS/APP survey at 4 μm

We present high-contrast imaging observations of seven protoplanetary disks at 4um using the ERIS on the VLT. This study focuses on detecting scattered light from micron-sized dust particles and assessing the potential of the vAPP coronagraph for disk and planet characterization. Observations were performed in pupil-stabilized mode with the vAPP coronagraph. Data were reduced using reference differential imaging and angular differential imaging techniques, incorporating principal component analysis for point-source detection. Contrast curves and detection limits were computed for planetary companions and disk features. The infrared disk signal was resolved in all systems, with first-time 4um detections around AS 209 and Elias 2-24, revealing mostly axisymmetric structures extending up to 60au. Two gaps were detected in the radial profiles of TW Hya (22au, 35au) and AS 209 (50au, 100au). For Elias 2-24, scattered light emission matched ALMA observations of inner disk structures, marking their first mid-infrared detection. In the case of HD 100546, the vAPP uncovered flared disk structures and faint spiral arms consistent with previous observations. HD 163296 shows a bright inner dust ring, confirming disk asymmetries and features, but we did not detect any planet candidate within the achieved contrast limits. The disk around PDS 70 exhibits clear features, with faint structures detected within the cavity. The observations achieved contrasts enabling the detection of planets down to 800 K, but no companions were detected, implying either low-mass planets, cooler formation scenarios, or a large dust extinction of Av>20 mag. The vAPP performed robustly for imaging structures in protoplanetary disks at 4um, providing critical insights into disk morphology and constraints on planet formation processes. No planetary-mass companions with temperatures >1000K are present in our sample.

astro-ph.EP↗

arXiv2025

The SPHERE infrared survey for exoplanets (SHINE). V. Complete observations, data reduction and analysis, detection performances, and final results

During the past decade, state-of-the-art planet-finder instruments like SPHERE@VLT, coupling coronagraphic devices and extreme adaptive optics systems, unveiled, thanks to large surveys, around 20 planetary mass companions at semi-major axis greater than 10 astronomical units. Direct imaging being the only detection technique to be able to probe this outer region of planetary systems, the SPHERE infrared survey for exoplanets (SHINE) was designed and conducted from 2015 to 2021 to study the demographics of such young gas giant planets around 400 young nearby solar-type stars. In this paper, we present the observing strategy, the data quality, and the point sources analysis of the full SHINE statistical sample as well as snapSHINE. Both surveys used the SPHERE@VLT instrument with the IRDIS dual band imager in conjunction with the integral field spectrograph IFS and the angular differential imaging observing technique. All SHINE data (650 datasets), corresponding to 400 stars, including the targets of the F150 survey, are processed in a uniform manner with an advanced post-processing algorithm called PACO ASDI. An emphasis is put on the classification and identification of the most promising candidate companions. Compared to the previous early analysis SHINE F150, the use of advanced post-processing techniques significantly improved by one or 2 magnitudes (x3-x6) the contrast detection limits, which will allow us to put even tighter constraints on the radial distribution of young gas giants. This increased sensitivity directly places SHINE as the largest and deepest direct imaging survey ever conducted. We detected and classified more than 3500 physical sources. One additional substellar companion has been confirmed during the second phase of the survey (HIP 74865 B), and several new promising candidate companions are awaiting second epoch confirmations.

astro-ph.EP↗

arXiv2025

A study of the frequency and characteristics of stellar companions and Jupiter-like planets in nearby open clusters

Observations of companions of solar-type stars in nearby young moving groups (NYMGs) show that they split into two groups: stellar and brown dwarf companions (mass ratio $q>0.05$) and Jupiter-like (JL) planets ($q<0.02$). The frequency of JL planets in NYMGs appears to be higher than that obtained from radial velocity (RV) surveys. We extended the search for companions to three nearby clusters of intermediate age: Hyades, Coma Berenices, and Ursa Major. They are older and formed in more massive events than the NYMGs. The sample of host stars is complete for the core of the clusters, while we considered only a fraction of the tidal tails. We used the same methods considered for the members of NYMGs. We obtained a fairly complete sample of stellar companions and detected six massive JL planets. We found a lower frequency of equal-mass companions than in the NYMGs; this might be related to how binaries form in these environments. We also observed a concentration of stellar binaries in the cores of Ursa Major and Coma Berenices; we attribute this to the selective loss of low-mass systems. The observed scarcity of wide companions in Hyades can be due to the destruction of binaries in close encounters. The frequency of JL planets is lower than in the NYMGs but similar to that obtained from RV surveys. This extends the correlation with age and mass previously found for NYMGs. Results of this study alone do not indicate whether age or mass are the factors driving the observed correlation. A comparison of the frequencies of free-floating planets from microlenses and in young associations favours mass as the main driving parameter. Once the initial cluster mass function is considered, the frequency of JL planets in NYMGs is consistent with the results obtained using RVs.

astro-ph.SR↗

arXiv2024

A multi-technique detection of an eccentric giant planet around accelerating star HD 57625

The synergy between different detection methods is a key asset in exoplanetology, allowing for both precise characterization of detected exoplanets and robust constraints even in the case of non-detection. Recently, the interplay between imaging, radial velocities and astrometry has produced significant advancements in exoplanetary science. We report a first result of an ongoing survey performed with SHARK-NIR, the new high-contrast near-infrared imaging camera at the Large Binocular Telescope, in parallel with LBTI/LMIRCam in order to detect planetary companions around stars with significant proper motion anomaly. In this work we focus on HD 57625, a F8 star for which we determine a $4.8^{+3.7}_{-2.9}$Ga age, exhibiting significant astrometric acceleration and for which archival radial velocities hint at the presence of a previously undetected massive long-period companion. We analyse the imaging data we collected with SHARK-NIR and LMIRCam in synergy with the available public SOPHIE radial velocity time series and Hipparcos-Gaia proper motion anomaly. With this joint multi-technique analysis, we aim at characterizing the companion responsible for the astrometric and radial velocity signals. The imaging observations result in a non-detection, indicating the companion to be in the substellar regime. This is confirmed by the synergic analysis of archival radial velocity and astrometric measurements resulting in the detection of HD 57625 b, a ${8.43}_{-0.91}^{+1.10}$M$_{\rm Jup}$ planetary companion with an orbital separation of ${5.70}_{-0.13}^{+0.14}$au and ${0.52}_{-0.03}^{+0.04}$ eccentricity. HD 57625 b joins the small but growing population of giant planets in outer orbits with true mass determination provided by the synergic usage of multiple detection methods, proving once again the importance of multi-technique analysis in providing robust characterization of planetary companions.

astro-ph.EP↗

arXiv2024

Deep imaging of three accelerating stars using SHARK-NIR and LMIRCam at LBT

The combination of detection techniques enhances our ability to identify companions orbiting nearby stars. We employed high-contrast imaging to constrain mass and separation of possible companions responsible for the significant proper motion anomalies of the nearby stars HIP 11696, HIP 47110 and HIP 36277. These targets were observed using the LBT's high-contrast camera, SHARK-NIR, in H-band using a Gaussian coronagraph, and with the LMIRCam instrument in the L'-band and using a vAPP coronagraph. Both observations were conducted simultaneously. Additionally, constraints at short separations from the host star are derived analyzing the renormalized unit weight error (RUWE) values from the Gaia catalogue. We find that the companion responsible for the anomaly signal of HIP 11696 is likely positioned at a distance from 2.5 to 28 astronomical units from its host. Its mass is estimated to be between 4 and 16 Jupiter masses, with the greater mass possible only at the upper end of the separation range. Similar limits were obtained for HIP 47110 where the companion should reside between 3 and 30 au with a mass between 3 and 10 MJup. For HIP 36277, we identified a faint stellar companion at large separation, though it might be substellar depending on the assumed age for the star. Considering the older age, this object accounts for the absolute value of the PMa vector but not for its direction. Additionally, we found a substellar candidate companion at a closer separation that could explain the PMa signal, considering a younger age for the system.

astro-ph.EP↗

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 $ρ$b=0.5+/-0.1 $ρ_{\oplus}$. 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.

astro-ph.EP↗

arXiv2024

A simple model for spectroscopic analyses of active stars

Spectroscopic analyses of young late-type stars suffer from systematic inaccuracies, typically under-estimating metallicities but over-estimating abundances of certain elements including oxygen and barium. Effects are stronger in younger and cooler stars, and recent evidence specifically indicates a connection to the level of chromospheric activity. We present here a two-component spectroscopic model representing a non-magnetic baseline plus a magnetic spot, and analyse the resulting synthetic spectra of young solar analogues using a standard spectroscopic technique. For a moderately active star with solar parameters and chromospheric activity index log R'_HK = -4.3 (~100 Myr), we predict that [Fe/H] is underestimated by 0.06 dex while v_mic is overestimated by 0.2 km/s; for higher activity levels we predict effects as large as 0.2 dex and 0.7 km/s. Predictions are in agreement with literature data on solar twins, and indicate that the model is a plausible explanation to the observed effects. The model is simple enough that it can be included in spectroscopic packages with only changes to the underlying spectrum synthesis modules, if a log R'_HK value is provided.

astro-ph.SR↗

arXiv2024

The GAPS Programme at TNG. LXI. Atmospheric parameters and elemental abundances of TESS young exoplanet host stars

The study of exoplanets at different evolutionary stages can shed light on their formation, migration, and evolution. The determination of exoplanet properties depends on the properties of their host stars. It is therefore important to characterise the host stars for accurate knowledge on their planets. Our final goal is to derive, in a homogeneous and accurate way, the stellar atmospheric parameters and elemental abundances of ten young TESS transiting planet-hosting GK stars followed up with the HARPS-N at TNG spectrograph within the GAPS programme. We derived stellar kinematic properties, atmospheric parameters, and abundances of 18 elements. Lithium line measurements were used as approximate age estimations. We exploited chemical abundances and their ratios to derive information on planetary composition. Elemental abundances and kinematic properties are consistent with the nearby Galactic thin disk. All targets show C/O<0.8 and 1.0<Mg/Si<1.5, compatible with silicate mantles made of a mixture of pyroxene and olivine assemblages. The Fe/Mg ratios, with values of $\sim$0.7-1.0, show a propensity for the planets to have big (iron) cores. All stars hosting very low-mass planets show Mg/Si values consistent with the Earth values, thus demonstrating their similar mantle composition. Hot Jupiter host stars show a lower content of O/Si, which could be related to the lower presence of water content. We confirm a trend found in the literature between stellar [O/Fe] and total planetary mass, implying an important role of the O in shaping the mass fraction of heavy elements in stars and their disks. The detailed host star abundances provided can be employed for further studies on the composition of the planets within the current sample, when their atmospheres will be exploited.

astro-ph.SR↗