arXiv subjects

F. Borsa

Publications and source records attributed to F. Borsa.

At least 19 recordsLinked to original sources

arXiv2026

The GAPS Programme at TNG LXXXI. The puzzle of the HeI absorption signal in the atmosphere of V1298 Tau b with GIARPS@TNG

Atmospheric escape shapes close-in planets mostly in their first tens of Myr. The young V1298Tau system (10-30Myr) is a benchmark for investigating photoevaporation and planetary evolution at early stages. The metastable HeI near-infrared triplet is a key proxy for atmospheric escape. We aim to detect and characterise HeI in the extended atmosphere of V1298Taub. We analysed four transits over a 4-year baseline using GIARPS (GIANO-B + HARPS-N) at the Telescopio Nazionale Galileo. We re-derived the projected spin-orbit angle by modelling the Rossiter-McLaughlin effect. Using simultaneous optical and near-infrared high-resolution transmission spectroscopy of V1298Taub, we monitored the HeI triplet alongside key chromospheric indicators ($\log R'_{HK}$, H$α$, and NaI) to disentangle stellar activity from planetary evaporation. While the stellar spectra show significant night-to-night variability, transmission spectroscopy reveals persistent HeI absorption across all four epochs. This contrasts with H$α$ and NaI, observed over two nights with simultaneous HARPS-N monitoring, which fluctuate between emission and absorption due to stellar activity. The consistent presence of HeI over 4 years may suggest a planetary origin, despite stellar-driven depth modulation. ATES hydrodynamic simulations show that stellar XUV flux variations modulate the HeI absorption depth and equivalent width. Furthermore, stellar wind fluctuations likely drive the observed night-to-night variability of the exospheric structure. The detection of HeI across all epochs may support planetary evaporation, despite modulation by stellar activity. Our results underscore that disentangling a planetary signal from stellar contamination remains challenging for highly active hosts; securing the planetary nature of the HeI signature requires activity monitoring and full transit coverage to establish a robust baseline.

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arXiv2026

Radio and high-energy variable emission from a multi-wavelength follow-up of the infant planet-hosting star V1298 Tau

V1298 Tau is a very young and magnetically active K1V star which hosts a benchmark multi-planetary system to study planet formation and evolutionary history at the earliest stages. Between 2025 and 2026, we conducted a campaign to monitor the variability of V1298 Tau in radio (band C), X-ray, and NUV bands, with the support of publicly available contemporary optical light curve, and to investigate multi-band correlations to link the emission with stellar activity. Radio observations were carried out with the Karl G. Jansky Very Large Array (JVLA) in band C (4.5--6.5 GHz). X-ray and NUV observations were carried out with the Swift satellite over 20 days, ending one month before the begin of the radio campaign. We analysed the temporal variability of peak (integrated) fluxes in the C-band and of X-ray (NUV) luminosities on various timescales, comparing it with the variability observed in the high-cadence optical light curve collected by the ASAS-SN survey. We observed both radio and high-energy time variable emission. JVLA detected emission in 90\% of the visits, switching between high ($\geq$0.1 mJy/beam) and low flux states in matter of days or hours. The fluxes show moderate correlation with the optical light curve, suggesting modulation with the stellar rotation period. Except for one visit, dynamic spectral analysis does not reveal short-term (minutes) variability, nor is there any evidence of circularly polarised emissions. Overall, the radio observations can be explained as gyrosynchrotron and/or cyclotron emission from the corona, and linked to stellar magnetic activity. At high-energy, we detected significant variability in X-ray luminosity (within the range ~1.2--2.5x10$^{+30}$ erg/s), the decay phase of a stellar flare, and evidence of correlation with the optical flux. Our data confirm that V1298\,Tau follows the near-linear Güdel-Benz relation.

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arXiv2026

High-resolution transmission spectroscopy of KELT-18b Metastable helium detection at 1083 nm

We present the first high-resolution transmission spectroscopy of the ultrahot Jupiter KELT-18b, probing its escaping atmosphere by analyzing a single transit obtained with the CARMENES spectrograph. Transmission spectroscopy and Doppler tomography were utilized to isolate the planetary signal. To mitigate contamination from the strong telluric OH lines overlapping the region of interest, two distinct data analysis procedures were applied: a standard Molecfit and OH-masking approach as well as a PCA-based method. By combining the two complementary approaches, we successfully detect a He\,I triplet absorption feature of $1.10 \pm 0.22\%$ ($5.1σ$). The signal exhibits a velocity shift consistent with zero and is attributed to the exoplanetary atmosphere. An injection test reveals that the PCA-based method significantly suppresses the retrieved signal. Additionally, using the ATES and TPM codes, we modeled the atmospheric photoevaporation and the helium triplet profile for different He/H ratios and stellar XUV fluxes, accounting for instrument and planetary rotational broadening. From our simulations we derive a mass-loss rate and an evaporation efficiency for KELT-18b of $10.47 \leq \log_{10}(\dot{M}) \leq 11.68$ and $0.153 \leq η\leq 0.321$, demonstrating that the atmosphere of KELT-18b is undergoing photoevaporation. Furthermore, our simulations show good agreement with the observed transmission spectrum, allowing us to exclude very low He/H ratios at a $3σ$ confidence level for XUV fluxes up to approximately twice the nominal reconstructed value. Our result expands the known parameter space of exoplanets with confirmed helium absorption, establishing KELT-18b as the most massive planet orbiting the hottest host star with such a detection.

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arXiv2026

The GAPS programme at TNG LXXXII. The first atmospheric investigation of the gas giant WASP-13b at high resolution with GIARPS

Low-density transiting gas giant exoplanets are key benchmarks for atmospheric studies. Despite their large-scale heights, many of them remain poorly characterised. We present the first atmospheric investigation at high-resolution of the inflated (R$_\mathrm{p}$$\sim$1.4 R$_{\mathrm{J}}$), hot Jupiter (T$\sim$1500$ \mathrm{K}$) WASP-13 b aiming at constraining its atmospheric composition and refine its orbital geometry. We analysed four transits observed with GIARPS at the TNG. Updated stellar and planetary parameters were re-derived from the most precise literature values, and a new Rossiter-McLaughlin analysis was performed to measure the projected spin-orbit angle ($λ$) and stellar rotational velocity ($v\sin{i_\star}$). Atmospheric signals were searched using high-resolution spectroscopy, both with cross-correlation and single-line analyses, targeting key atomic and molecular species (e.g. \ion{He}{I}, H$α$, \ion{Na}{I}, H$_2$O, CO). We find a well-aligned orbit ($λ$ = 2.7$\pm$1.1$^\circ$) and $v\sin{i_\star}$ = 4.5$\pm$0.1 km s$^{-1}$, improving upon previous constraints. No significant atmospheric absorption is detected in either VIS or NIR data. Injection-and-recovery tests exclude an isothermal atmosphere with metallicity [M/H]$\lesssim$10$\times$[M/H]$_\odot$ and simultaneously a grey cloud top pressure P$_{\rm cloud}\gtrsim10$ mbar, under the assumption of chemical equilibrium. WASP-13 b appears to belong to the class of low-density hot Jupiters with weak or featureless transmission spectra, most likely shaped by the presence of high-altitude clouds. Although a highly metal-enriched atmosphere cannot be fully excluded, current evidence disfavours this scenario. Further observations with next-generation facilities will be essential to characterise the atmospheric properties of this challenging target.

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arXiv2026

The GAPS programme at TNG LXXVIII. Phase-resolved detection of multiple atomic species in the atmosphere of KELT-20b/MASCARA-2b

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 HI, NaI, MgI, CrI, FeI, and FeII, and tentatively detect CrII. We further report new detections of KI, CaI, VI, MnI, and BaII, and a tentative detection of PrI 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 Kp-Vsys maps, notably in CaI, VI, CrI, and FeI, consistent with absorption arising from two distinct atmospheric limbs of the planet.

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arXiv2026

High-resolution detection of reflected light from the exo-Neptune LTT-9779 b

While high-resolution spectroscopy is routinely used to probe exoplanetary atmospheres, detecting reflected starlight remains highly challenging due to the extremely low planet-to-star optical flux ratios. We report the detection of reflected light from the ultra-hot exo-Neptune LTT-9779 b using high-resolution spectroscopy with ESPRESSO in its 4UT mode. By combining multiple epochs and applying a cross-correlation analysis with a theoretical reflection kernel, we were able to identify a faint signal matching the expected morphological and kinematic profile of the planetary reflection. This signature, whose presence has been detected at a signal-to-noise ratio of $\sim$5.4, exhibits a radial velocity semi-amplitude consistent with the expected orbital motion. We measured the planet-to-star flux ratio from the ratio of the equivalent widths of the planetary and stellar cross-correlation functions, finding $F_{\mathrm{p}}/F_\star = 102^{+29}_{-30}$ ppm for the ESPRESSO 380--770 nm wavelength range. Assuming a Lambertian phase function, this corresponds to a geometric albedo of $A_{\mathrm{g}} = 0.88 \pm 0.25$. The inferred albedo is consistent with previous space-based photometric measurements, suggesting a highly reflective atmosphere potentially dominated by scattering processes or high-altitude clouds. While we show that reflectivity is enhanced towards blue wavelengths, a detailed spectroscopic characterization of the planetary atmosphere from the reflected-light signal remains out of reach. This result highlights the scientific potential of future high-resolution spectrographs on extremely large telescopes, paving the way for systematic reflected-light detections across a broader exoplanet population, including cooler and smaller planets.

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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 $λ= 341.1^{+2.3}_{-2.5}$ deg. Using our knowledge of the stellar rotation period ($3.00 \pm 0.02$ d), we estimated a true obliquity of $ψ= 25.9^{+7.5}_{-6.3}$ 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 $ψ$ 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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arXiv2025

The GAPS Programme at TNG. LXIX.The Dayside of WASP-76b revealed by GIANO-B, HARPS-N and ESPRESSO: Evidence for Three-Dimensional Atmospheric Effects

The study of the atmosphere of ultra-hot Jupiters (UHJs) with equilibrium temperature $\geq$2000 K provides valuable insights into atmospheric physics under such extreme conditions. We aim to characterise the dayside thermal spectrum of the UHJ WASP-76b and investigate its properties. We analysed data gathered with three high-resolution spectrographs, specifically two nights with simultaneous observations of HARPS-N and GIANO-B, and four nights of publicly available ESPRESSO optical spectra. We observed the planet's dayside covering orbital phases between quadratures (0.25 < $ϕ$ < 0.75). We performed a homogeneous analysis of the GIANO-B, HARPS-N and ESPRESSO data and co-added the signal of thousands of planetary lines through cross-correlation with simulated spectra of the planetary atmosphere. We report the detection of CO in the dayside atmosphere of WASP-76b with a signal-to-noise ratio (S/N) of 10.4 in the GIANO-B spectra. In addition, we detect Fe I in both the HARPS-N and ESPRESSO datasets, with S/N of 3.5 and 6.2, respectively. A signal from Fe I is also identified in one of the two GIANO-B observations, with a S/N of 4.0. Interestingly, a qualitatively similar pattern - with a weaker detection in one epoch compared to the other - is also observed in the two HARPS-N nights. The GIANO-B results are therefore consistent with those obtained with HARPS-N. Finally, we compared our strongest detections of CO (GIANO-B) and Fe I (ESPRESSO), with predictions from Global Circulation Models (GCMs). Both cross-correlation and likelihood analyses favour the GCM that includes atmospheric dynamics over a static (no-dynamics) model when applied to the ESPRESSO data. This study adds to the growing body of literature employing GCMs to interpret high-resolution spectroscopic measurements of exoplanet atmospheres.

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arXiv2025

NLTE atmospheric modelling of the ultra-hot Jupiter WASP-178b and comparison with UV and optical observations

We model the atmosphere of the ultra-hot Jupiter (UHJ) WASP-178b accounting for NLTE effects and compare synthetic transmission spectra with NUV and optical observations. We use the HELIOS code (LTE) in the lower and the Cloudy code (LTE or NLTE) in the middle and upper atmosphere to compute the temperature-pressure (TP) and abundance profiles. We further use Cloudy to compute the theoretical planetary transmission spectrum both in LTE and NLTE for comparison with observations. We find an isothermal TP profile at pressures higher than 10 mbar and lower than 10$^{-8}$ bar, with an almost linear increase from about 2200 K to about 8100 K in between. The temperature structure is driven by NLTE effects, particularly in the form of increased heating resulting from the overpopulation of long-lived FeII levels with strong transitions in the NUV band, where the stellar emission is strong, and of decreased cooling due to the underpopulation of MgI and MgII levels that dominate the cooling. The planetary atmosphere is hydrostatic up to pressures of about 1 nbar, and thus accurately modelling spectral lines forming at pressures lower than about 1 nbar requires accounting for both hydrodynamics and NLTE effects. The NLTE synthetic transmission spectrum overestimates the observed H$α$ and H$β$ absorption, while the LTE model is in good agreement, which is surprising as the opposite has been found for the other UHJs for which NLTE modelling has been performed. Instead, in the NUV we find an excellent match between the NLTE transmission spectrum and the HST/UVIS data, contrary to the LTE model. This contrasts previous LTE results requiring SiO absorption to fit the observations. The accurate characterisation of the atmosphere of UHJs is possible only accounting for NLTE effects, and particularly for the level population of Fe and Mg, which dominate heating and cooling, respectively.

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arXiv2025

Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode

Transit spectroscopy usually relies on the integration of one or several transits to achieve the S/N necessary to resolve spectral features. Consequently, high-S/N observations of exoplanet atmospheres are essential for disentangling the complex chemistry and dynamics beyond global trends. In this study, we combined two partial 4-UT transits of the ultrahot Jupiter WASP-121 b, observed with the ESPRESSO at the VLT in order to revisit its titanium chemistry. Through cross-correlation analysis, we achieved detections of H I, Li I, Na I, K I, Mg I, Ca I, Ti I, V I, Cr I, Mn I, Fe I, Fe II, Co I, Ni I, Ba II, Sr I, and Sr II. Additionally, narrow-band spectroscopy allowed us to resolve strong single lines, resulting in significant detections of H$α$, H$β$, H$γ$, Li I, Na I, K I, Mg I, Ca II, Sr I, Sr II, and Mn I. Our most notable finding is the high-significance detection of Ti I ($\sim$ 5$σ$ per spectrum, and $\sim$ 19$σ$ stacked in the planetary rest frame). Comparison with atmospheric models reveals that Ti I is indeed depleted compared to V I. We also resolve the planetary velocity traces of both Ti I and V I, with Ti I exhibiting a significant blueshift toward the end of the transit. This suggests that Ti I primarily originates from low-latitude regions within the super-rotating jet observed in WASP-121 b. Our observations suggest limited mixing between the equatorial jet and the mid-latitudes, in contrast with model predictions from GCMs. We also report the non-detection of TiO, which we attribute to inaccuracies in the line list that could hinder its detection, even if present. Thus, the final determination of the presence of TiO must await space-based observations. We conclude that the 4-UT mode of ESPRESSO is an excellent testbed for achieving high S/N on relatively faint targets, paving the way for future observations with the ELT.

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arXiv2024

The GAPS programme at TNG LXVI. A homogeneous search for Na i and its possible variability in ten gas giant exoplanets

The neutral sodium resonance doublet (Na i D) has been detected in the upper atmosphere of several close-in gas giants, through high-resolution transmission spectroscopy. We aim to investigate whether its variability is linked to the planets' properties, the data quality, or the accuracy of the system parameters used. Using the public code SLOPpy, we extracted the transmission spectrum in the Na i D region of ten gas giants for which a large number of HARPS-N observations are available. We modelled the absorption signals found, performing an MCMC analysis, and converted the measured absorption depth to the corresponding atmospheric height over which most sodium absorption occurs. While two targets (GJ 436 b and KELT-7 b) show no Na i D feature, we found variability in the transmission spectrum of the other targets. Three of them (HD 209458 b, WASP-80 b, and WASP-127 b) present absorption on only some nights, while in the other five targets (HD 189733 b, KELT-9 b, KELT-20 b, WASP-69 b, and WASP-76 b), a significant absorption signal is present on most of the nights analysed. Except for WASP-69 b, the measured absorption depths lead to a ratio of the two Na I D depths that is compatible with or slightly larger than one. As was expected from literature, the relative atmospheric height follows an empirical exponential trend as a function of a scaled product of the planet's equilibrium temperature and surface gravity. We confirm the sodium detection on HD 189733 b, KELT-9 b, KELT-20 b, WASP-69 b, and WASP-76 b. The signal detected in WASP-127 b requires further observations for definitive confirmation. We exclude a planetary origin for the signals found on HD 209458 b and WASP-80 b. The sodium absorption variability does not appear to be related to planetary properties, but rather to data quality, sub-optimal data treatment, or stellar activity.

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arXiv2024

The GAPS programme at TNG -- LXIII. Photo-evaporating puzzle: Exploring the enigmatic nature of TOI-5398 b atmospheric signal

Atmospheric characterization is key to understanding exoplanetary systems, offering insights into the planets current and past conditions. By analyzing key lines like H alpha and the He I triplet, we can trace the evolution of planets through atmospheric photo-evaporation. While ultra-hot Jupiters have been the focus for years, attention is shifting toward smaller, colder planets, which are more challenging to study due to weaker signals, requiring more precise techniques. This study aims to characterize the atmosphere of TOI-5398 b, a warm Saturn with a 10.59-day orbit around a young (650 Myr) G-type star. The system also hosts a smaller inner planet, TOI-5398 c, with a 4.77-day orbit. Both planets are ideal for atmospheric studies due to their proximity to the host star, which drives strong photo-evaporation, especially in planet b, whose high transmission spectroscopy metric (288) makes it a prime target. We analyzed data from a transit observed with the HARPS-N and GIANO-B high-resolution spectrographs, using cross-correlation and single-line analysis to search for atomic species. During this observation, planet c was also transiting, so we investigated the source of the signals. Based on photo-evaporation models, we attribute the signal mainly to planet b, which is expected to lose more mass. We detected H alpha and He I triplets, key markers of photo-evaporation, corresponding to atmospheric heights of 2.33 Rp and 1.65 Rp, respectively. The ATES models supported our observations, predicting a similar He I absorption for planet b and suggesting an He/H ratio of 1/99. Additionally, we detected an Na I doublet via single-line analysis, though cross-correlation did not reveal other atomic species.

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arXiv2024

The GAPS programme at TNG: TBD. Studies of atmospheric FeII winds in ultra-hot Jupiters KELT-9b and KELT-20b using HARPS-N spectrograph

Ultra-hot Jupiters (UHJs) are gas giant planets orbiting close to their host star, with equilibrium temperatures exceeding 2000 K, and among the most studied planets in terms of their atmospheric composition. Thanks to a new generation of ultra-stable high-resolution spectrographs, it is possible to detect the signal from the individual lines of the species in the exoplanetary atmospheres. We employed two techniques in this study. First, we used transmission spectroscopy, which involved examining the spectra around single lines of FeII. Then we carried out a set of cross-correlation studies for two UHJs: KELT-9b and KELT-20b. Both planets orbit fast-rotating stars, which resulted in the detection of the strong Rossiter-McLaughlin (RM) effect and center-to-limb variations in the transmission spectrum. These effects had to be corrected to ensure a precise analysis. Using the transmission spectroscopy method, we detected 21 single lines of FeII in the atmosphere of KELT-9b. All of the detected lines are blue-shifted, suggesting strong day-to-night side atmospheric winds. The cross-correlation method leads to the detection of the blue-shifted signal with a signal-to-noise ratio (S/N) of 13.46. Our results are in agreement with models based on non-local thermodynamical equilibrium (NLTE) effects, with a mean micro-turbulence of nu_mic = 2.73 +/- 1.5 km/s and macro-turbulence of nu_mac = 8.22 +/- 3.85 km/s. In the atmosphere of KELT-20b, we detected 17 single lines of FeII. Considering different measurements of the systemic velocity of the system, we conclude that the existence of winds in the atmosphere of KELT-20b cannot be determined conclusively. The detected signal with the cross-correlation method presents a S/N of 11.51. The results are consistent with NLTE effects, including means of nu_mic = 3.04 +/- 0.35 km/s and nu_mac = 6.76 +/- 1.17 km/s.

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arXiv2024

The obliquity and atmosphere of the hot Jupiter WASP-122b (KELT-14b) with ESPRESSO: An aligned orbit and no sign of atomic or molecular absorption

Thanks to their short orbital periods and hot extended atmospheres, hot Jupiters are ideal candidates for atmosphere studies with high-resolution spectroscopy. New stable spectrographs help improve our understanding of the evolution and composition of those types of planets. By analyzing two nights of observations using the ESPRESSO high-resolution spectrograph, we studied the architecture and atmosphere of hot Jupiter WASP-122b (KELT-14b). By analyzing the Rossiter-McLaughlin (RM) effect, we measured the spin-orbit angle of the system to be lambda = 0.09 +0.88/-0.90 deg. This result is in line with literature obliquity measurements of planetary systems around stars with effective temperatures cooler than 6500 K. Using the transmission spectroscopy, we studied the atmosphere of the planet. Applying both the single-line analysis and the cross-correlation method, we looked for Ca I, Cr I, FeH, Fe I, Fe II, H2O, Li I, Mg I, Na I, Ti I, TiO, V I, VO, and Y I. Our results show no evidence of any of these species in WASP-122b's atmosphere. The lack of significant detections can be explained by either the RM effect covering the regions where the atmospheric signal is expected and masking it, along with the low signal-to-noise ratio (S/N) of the observations or the absence of the relevant species in its atmosphere.

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arXiv2024

ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b

Ultra hot Jupiters (gas giants, Teq>2000 K) are intriguing exoplanets due to their extreme atmospheres. Their torrid daysides can be characterised using ground-based high-resolution emission spectroscopy. We search for signatures of neutral and singly ionised iron (Fe I and Fe II) in the dayside of the ultra hot Jupiter WASP-76 b, as these species were detected via transmission spectroscopy in this exoplanet. Furthermore, we aim to confirm the existence of a thermal inversion layer, which has been reported in previous studies, and attempt to constrain its properties. We observed WASP-76 b on four epochs with ESPRESSO at the VLT, at orbital phases shortly before and after the secondary transit, when the dayside is in view. We present the first analysis of high-resolution optical emission spectra for this exoplanet. We compare the data to synthetic templates from petitRADTRANS, using cross-correlation function techniques. We detect a blueshifted (-4.7+-0.3 km/s) Fe I emission signature on the dayside of WASP-76 b at 6.0-sigma. The signal is detected independently both before and after the eclipse, and blueshifted in both cases. The presence of iron emission features confirms the existence of a thermal inversion layer. Fe II was not detected, possibly because this species is located in the upper layers of the atmosphere, which are more optically thin. Thus the Fe II signature on the dayside of WASP-76 b is too weak to be detected with emission spectroscopy. We propose that the blueshifted Fe I signature is created by material rising from the hot spot to the upper layers of the atmosphere, and discuss possible scenarios related to the position of the hotspot. This work unveils some of the dynamic processes ongoing on the dayside of WASP-76 b through the analysis of the Fe I signature from its atmosphere, and complements previous knowledge obtained from transmission studies.

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arXiv2024

The GAPS programme at TNG LX Atmospheric characterisation of KELT-9 b via single-line analysis: Detection of six H I Balmer lines, Na I, Ca I, Ca II, Fe I, Fe II, Mg I, Ti II, Sc II, and Cr II

We analysed six primary transits of the ultra-hot Jupiter KELT-9,b obtained with the HARPS-N high-resolution spectrograph in the context of the Global Architecture of Planetary Systems (GAPS2) project, to characterise the atmosphere via single-line analysis. We extracted the transmission spectrum of each individual line by comparing the master out-of-transit spectrum with the in-transit spectra and computing the weighted average of the tomography in the planet reference frame. We corrected for the centre-to-limb variation and the Rossiter-McLaughlin effect by modelling the region of the star disc obscured by the planet during the transit and subtracting it from the master-out spectrum. We detected all six observable lines of the Balmer series within the HARPS-N wavelength range, from H$α$ to H$ζ$, with a significance exceeding 5$σ$. We focussed on metal species, detecting Na I, Ca I, Ca II, Fe I, Fe II, Mg I, Ti II, Sc II, and Cr II lines. This is the first detection in the atmosphere of an exoplanet of H$ε$ and H$ζ$ lines, as well as of individual lines of Sc II and Cr II. Our detections are supported by a comparison with published synthetic transmission spectra of KELT-9b obtained accounting for non-local thermodynamic equilibrium effects. The results underline the presence of a systematic blueshift due to night-side to day-side winds. The single-line analysis allowed us not only to assess the presence of atomic species in the atmosphere of KELT-9 b, but also to further characterise the local stratification of the atmosphere. Coupling the height distribution of the detected species with the velocity shift retrieved, we acknowledged the height distribution of night-side to day-side winds. Moreover, the study of the rotational broadening of different species supports the prediction of a tidally locked planet rotating as a rigid body.

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arXiv2024

The time evolution of the ultraviolet habitable zone

For stars hosting Circumstellar Habitable Zone (CHZ) exoplanets, we investigate the time-evolution of their ultraviolet habitable zone (UHZ), the annular region around a star where an exoplanet could experience a suitable ultraviolet environment for the presence and emergence of life, and the possible intersection of the UHZ with the CHZ. To estimate their UV luminosity evolution, and therefore the evolution of their UHZ, we analyse Swift-UV/Optical telescope observations and adopt the near-UV luminosity evolutionary tracks derived using GALEX observations of young moving groups. We find that an intersection between CHZ and UHZ could exist (or have existed) around all stars of our sample at different epochs, except for the coldest M-dwarfs (temperature < 2800 K, e.g. Trappist-1). For hotter M-dwarfs the formation of RNA precursors through cyanosulfidic chemistry triggered by near-UV radiation could occur during the first 1-2 Gyrs. The radial-extension and time-duration of the CHZ-UHZ intersection increase with the stellar effective temperature and the exoplanet atmospheric transmissivity at near-UV wavelengths. Within our sample, Proxima Centauri represents a golden target for the quest of life outside the Solar system because it experienced a long-lasting and more extended, compared to similar M-dwarfs, CHZ-UHZ intersection.

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arXiv2024

ANDES, the high resolution spectrograph for the ELT: science goals, project overview and future developments

The first generation of ELT instruments includes an optical-infrared high-resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of $\sim$100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 $μ$m with the goal of extending it to 0.35-2.4 $μ$m with the addition of a U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allow ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases, there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states.

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