arXiv subjects

M. Brogi

Publications and source records attributed to M. Brogi.

At least 19 recordsLinked to original sources

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 Neptunian ridge planet WASP-156 b does not have a polar orbit

The population of short-period exo-Neptunes is thought to be shaped by an interplay between different dynamical mechanisms, such as orbital migration and tidal effects, and photoevaporation. We can gain insight into these processes by studying observables such as the stellar obliquity. Here we study the Rossiter-McLaughlin (RM) effect and measure the projected obliquity, $\lambda$, of the Neptunian ridge planet WASP-156 b. We analyse new ESPRESSO and MAROON-X spectroscopic transit observations, and new NGTS photometry simultaneous to the ESPRESSO data. Our analyses show an aligned orbit ($\lambda=-8\pm16^\circ$, based on the ESPRESSO observations), in contrast to a previous report of a highly misaligned orbit. We also find the star's projected rotational velocity to be $v \sin i_\mathrm{\star}\leq2$ km/s from spectral line modelling and $v \sin i_\mathrm{\star}=0.40\pm0.11$ km/s from the RM modelling. This is lower than the previously reported value of $\sim4$ km/s, which could partly explain the previously derived polar orbit. We also update the system's orbital parameters and rule out Jupiter-mass companions within 5 au using long-term radial velocity data. The planet's aligned and circular orbit ($e<0.16$ at $3\sigma$), and lack of nearby massive companions, are consistent with in situ formation or early disc-driven migration. Our findings move WASP-156 b from a tentative cluster of close-in Neptunes in polar orbits to the group of aligned Neptunes.

astro-ph.EP↗

arXiv2025

The GAPS programme at TNG LXX. HD 128717 B/Gaia-6 B: a long-period eccentric low-mass brown dwarf from astrometry and radial velocities

The transition regime between giant planets (GPs) and brown dwarfs (BDs) is still an open subject of study in exoplanetary science. A complete understanding of the population of long-period GPs and BDs would be pivotal in understanding this topic, but the number of such objects with precisely measured orbital and physical parameters is still small. Moreover, their dynamical influence on smaller companions in inner orbits is still unclear. Within the GAPS programme, we aim to confirm and characterize sub-stellar companion candidates from Gaia DR3, and to study the potential presence of additional lower-mass planets in their systems. We present the results of an intensive high-precision RV monitoring of HD 128717, which hosts the astrometric candidate Gaia-ASOI-009. We used the HARPS-N spectrograph at TNG to collect a high-cadence RV time series of the target. We used MCMC analyses to refine the Gaia DR3 orbital solution of the companion and, finally, performed a combined model of RV and proper motion anomaly (PMa) to derive the complete 3-D orbit of the companion. We also ran a suite of numerical simulations to confirm our results. We confirm the sub-stellar nature of Gaia-ASOI-009, i.e. Gaia-6 B: from the combined RV+PMa fit, we confirm that it is a high-eccentricity low-mass brown dwarf with $P_\text{B} = 9.37^{+0.06}_{-0.05}$ yr, $M_\text{B} = 19.8 \pm 0.5$ $M_\text{J}$, $e_\text{B}=0.85$, $i_\text{B} = 130^{\circ}$. The derived orbital solution differs significantly from the one published in Gaia DR3. Through a series of dedicated simulations, we demonstrate that this discrepancy arises from a degeneracy in the Gaia DR3 astrometric solution. Specifically, the combination of Gaia-6 B long orbital period and high eccentricity, both poorly constrained by the limited timespan of DR3, led to an incorrect solution characterized by a shorter period and lower eccentricity.

astro-ph.EP↗

arXiv2025

Mass determination of the three long-period Neptune- and sub-Neptune-sized planets transiting TOI-282

TOI-282 is a bright (V=9.38) F8 main-sequence star known to host three transiting long-period ($P_b$=22.9 d, $P_c$=56.0 d, and $P_d$=84.3 d) small ($R_p\approx$ 2-4 $R_{\oplus}$) planets. The orbital period ratio of the two outermost planets, namely TOI-282 c and d, is close to the 3:2 commensurability, suggesting that the planets might be trapped in a mean motion resonance. We combined space-borne photometry from the TESS telescope with high-precision HARPS and ESPRESSO Doppler measurements to refine orbital parameters, measure the planetary masses, and investigate the architecture and evolution of the system. We performed a Markov chain Monte Carlo joint analysis of the transit light curves and radial velocity time series, and carried out a dynamical analysis to model transit timing variations and Doppler measurements along with N-body integration. In agreement with previous results, we found that TOI-282 b, c, and d have radii of $R_b=2.69 \pm 0.23 \ R_{\oplus}$, $R_c=4.13^{+0.16}_{-0.14} \ R_{\oplus}$, and $R_d=3.11 \pm 0.15 \ R_{\oplus}$, respectively. We measured planetary masses of $M_b=6.2\pm1.6 \ M_{\oplus}$, $M_c=9.2\pm2.0 \ M_{\oplus}$, and $M_d=5.8^{+0.9}_{-1.1} \ M_{\oplus}$, which imply mean densities of $\rho_b=1.8^{+0.7}_{-0.6} \ \text{g cm}^{-3}$, $\rho_c=0.7 \pm 0.2 \ \text{g cm}^{-3}$, and $\rho_d=1.1^{+0.3}_{-0.2} \ \text{g cm}^{-3}$, respectively. The three planets may be water worlds, making TOI-282 an interesting system for future atmospheric follow-up observations with JWST and ELT.

astro-ph.EP↗

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 < $\phi$ < 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.

astro-ph.EP↗

arXiv2025

The GAPS Programme at TNG LXVII. Detection of water and preliminary characterisation of the atmospheres of the two hot Jupiters KELT-8 b and KELT-23 Ab

Expanding the number of hot giant planets with atmospheric characterisation can improve our understanding of their atmospheres as well as their formation and evolution mechanisms. In this work, we use high-resolution spectroscopy in the near-infrared (NIR) to search for chemical signatures in the atmosphere of the two hot Jupiters KELT-8 b and KELT-23 Ab, and perform a first characterisation of their atmospheric properties. We measured the transmission spectrum of each target with the NIR high-resolution spectrograph GIANO-B at the TNG and searched for atmospheric signals by cross-correlating the data with synthetic transmission spectra. In order to characterise the chemical-physical properties of the two atmospheres, we ran two different atmospheric retrievals for each dataset: a retrieval assuming chemical equilibrium and a `free-chemistry' retrieval, in which the abundance of each molecule could vary freely. We detect H$_2$O in the atmospheres of KELT-8 b and KELT-23 Ab with an S/N = 6.6 and S/N = 4.2, respectively. The two retrievals indicate a water-rich atmosphere for both targets. For KELT-8 b, we determine a water volume mixing ratio of log$_{10}$(VMR$_{\rm H_2O})=-2.07^{+0.53}_{-0.72}$, a metallicity of [M/H] $=0.77^{+0.61}_{-0.89}$ dex, and a sub-solar C/O ratio (C/O $\leq0.30$, at $2\,\sigma$). For KELT-23 Ab, we find log$_{10}$(VMR$_{\rm H_2O})=-2.26^{+0.75}_{-1.24}$, [M/H] $=-0.42^{+1.56}_{-1.35}$ dex, and C/O ratio $\leq0.78$ (at $2\,\sigma$). Comparing these chemical properties with those of the host stars, we suggest that, for both planets, the accretion of gaseous material occurred within the H$_2$O snowline in a pebble-rich disk enriched in oxygen due to sublimation of water ice from the inward-drifting pebbles. In conclusion, we measure the atmospheric signals of KELT-8 b and KELT-23 Ab for the first time and place first constraints on their properties.

astro-ph.EP↗

arXiv2024

Time Resolved Absorption of Six Chemical Species With MAROON-X Points to Strong Drag in the Ultra Hot Jupiter TOI-1518 b

Wind dynamics play a pivotal role in governing transport processes within planetary atmospheres, influencing atmospheric chemistry, cloud formation, and the overall energy budget. Understanding the strength and patterns of winds is crucial for comprehensive insights into the physics of ultra-hot Jupiter atmospheres. This study focuses on unraveling the wind dynamics and the chemical composition in the atmosphere of the ultra-hot Jupiter TOI-1518 b. Two transit observations using the high-resolution (R{\lambda} = 85 000), optical (spectral coverage between 490 and 920 nm) spectrograph MAROON-X were obtained and analyzed to explore the chemical composition and wind dynamics using the cross-correlation techniques, global circulating models, and atmospheric retrieval. We report the detection of 14 species in the atmosphere of TOI-1518 b through cross-correlation analysis. Additionally, we measure the time-varying cross-correlation trails for 6 different species, compare them with predictions from General Circulation Models (GCM) and conclude that a strong drag is present in TOI-1518b's atmosphere. We find that the trails are species-dependent. Fe+ favors a stronger drag than Fe, which we interpret as a sign of magnetic effects being responsible for the observed strong drag. Furthermore, we show that Ca+ probes layers above the Roche lobe, leading to a qualitatively different trail than the other species. Finally, we use a retrieval analysis to characterize the abundance of the different species detected. That analysis is refined thanks to the updated planetary mass we derived from the radial-velocity detection using SOPHIE data. We measure an abundance of iron corresponding to 0.07 to 1.62 solar enrichment. The retrievals appear to be biased for the other elements, probably due to the different Kp/Vsys shifts between iron and the other elements, which we demonstrate in the case of VO.

astro-ph.EP↗

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.

astro-ph.EP↗

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$\alpha$ to H$\zeta$, with a significance exceeding 5$\sigma$. 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$\epsilon$ and H$\zeta$ 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.

astro-ph.EP↗

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 $\mu$m with the goal of extending it to 0.35-2.4 $\mu$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 Coud\'e 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.

astro-ph.IM↗

arXiv2024

Doppler Tomography as a tool for characterising exoplanet atmospheres II: an analysis of HD 179949 b

High-resolution Doppler spectroscopy provides an avenue to study the atmosphere of both transiting and non-transiting planets. This powerful method has also yielded some of the most robust atmospheric detections to date. Currently, high-resolution Doppler spectroscopy detects atmospheric signals by cross-correlating observed data with a model atmospheric spectrum. This technique has been successful in detecting various molecules such as H2O, CO, HCN and TiO, as well as several atomic species. Here we present an alternative method of performing high-resolution Doppler spectroscopy, using a technique known as Doppler tomography. We present an analysis of HD 179949 b using Doppler tomography and provide Doppler tomograms confirming previous detections of CO at 2.3 microns, and H2O at both 2.3 microns, and 3.5 microns within the atmosphere of HD 179949 b, showing significantly lower background noise levels when compared to cross-correlation methods applied to the same data. We also present a novel detection of H2O at 2.1 microns, as well as a tentative detection of CO on the night side of the planet at 2.3 microns. This represents the first observational evidence for molecular absorption in the night-side emission spectrum of an exoplanet using Doppler spectroscopy.

astro-ph.EP↗

arXiv2024

The GAPS Programme at TNG LV. Multiple molecular species in the atmosphere of HAT-P-11 b and review of the HAT-P-11 planetary system

The atmospheric characterisation of hot and warm Neptune-size exoplanets is challenging due to their small radius and atmospheric scale height. The warm-Neptune HAT-P-11b is a remarkable target for such characterisation due to the large brightness of its host star (V=9.46 mag; H=7.13 mag). The aims of this work are to review the main physical and architectural properties of the HAT-P-11 planetary system, and to probe the presence of 8 molecular species in the atmosphere of HAT-P-11b at high spectral resolution in the near-infrared. The planetary system was reviewed by analysing transits and occultations of HAT-P-11b from the Kepler data set as well as HIRES at Keck archival radial-velocity (RV) data. We modelled the latter with Gaussian-process regression and a combined quasi-periodic and squared-exponential kernel to account for stellar variations on both (short-term) rotation and (long-term) activity-cycle timescales. In order to probe the atmospheric composition of HAT-P-11b, we observed 4 transits of this target with GIANO-B at TNG. We find that the long-period ($P\sim9.3$ years) RV signal previously attributed to planet HAT-P-11c is more likely due to the stellar magnetic activity cycle. Nonetheless, the Hipparcos-Gaia difference in the proper-motion anomaly suggests that an outer-bound companion might still exist. For HAT-P-11b, we measure a radius $R_{\rm p}=0.4466\pm0.0059\,R_{\rm J}$, a mass $M_{\rm p}=0.0787\pm0.0048\,M_{\rm J}$, and an eccentricity $e=0.2577^{+0.0033}_{-0.0025}$, in accordance with values in the literature. Probing its atmosphere, we detect $NH_3$ (S/N$=5.3$, significance$=5.0\sigma$) and confirm the presence of $H_2O$ (S/N$=5.1$, significance$=3.4\sigma$). We also tentatively detect the signal of $CO_2$ (S/N$=3.0$, significance$=3.2\sigma$) and $CH_4$ (S/N$=4.8$, significance$=2.6\sigma$), whose presence need to be confirmed by further observations.

astro-ph.EP↗

arXiv2024

The EBLM project -- XIII. The absolute dynamical masses of the circumbinary planet host TOI-1338/BEBOP-1

High-contrast eclipsing binaries with low mass M-dwarf secondaries are precise benchmark stars to build empirical mass-radius relationships for fully convective low-mass ($\rm M_{*} < 0.35\,M_{\rm sun}$) dwarf stars. The contributed light of the M-dwarf in such binaries is usually much less than one~per~cent at optical wavelengths. This enables the detection of circumbinary planets from precise radial velocity measurements. High-resolution cross-correlation techniques are typically used to detect exoplanet atmospheres. One key aspect of these techniques is the post-processing, which includes the removal of telluric and spectral lines of the host star. We introduce the application of such techniques to optical high-resolution spectra of the circumbinary planet-host TOI-1338/BEBOP-1, turning it effectively into a double-lined eclipsing binary. By using simulations, we further explore the impact of post-processing techniques for high-contrast systems. We detect the M-dwarf secondary with a significance of 11-$\sigma$ and measure absolute dynamical masses for both components. Compared to previous model-dependent mass measurements, we obtain a four times better precision. We further find that the post-processing results in negligible systematic impact on the radial velocity precision for TOI-1338/BEBOP-1 with more than $96.6\,$per~cent (1-$\sigma$) of the M-dwarf's signal being conserved. We show that these methods can be used to robustly measure dynamical masses of high-contrast single-lined binaries providing important benchmark stars for stellar evolution particularly near the bottom of the main sequence. We also demonstrate how to retrieve the phase curve of an exoplanet with high-resolution spectroscopy using our data.

astro-ph.EP↗

arXiv2023

The GAPS Programme at TNG L -- TOI-4515 b: An eccentric warm Jupiter orbiting a 1.2 Gyr-old G-star

Context. Different theories have been developed to explain the origins and properties of close-in giant planets, but none of them alone can explain all of the properties of the warm Jupiters (WJs, Porb = 10 - 200 days). One of the most intriguing characteristics of WJs is that they have a wide range of orbital eccentricities, challenging our understanding of their formation and evolution. Aims. The investigation of these systems is crucial in order to put constraints on formation and evolution theories. TESS is providing a significant sample of transiting WJs around stars bright enough to allow spectroscopic follow-up studies. Methods. We carried out a radial velocity (RV) follow-up study of the TESS candidate TOI-4515 b with the high-resolution spectrograph HARPS-N in the context of the GAPS project, the aim of which is to characterize young giant planets, and the TRES and FEROS spectrographs. We then performed a joint analysis of the HARPS-N, TRES, FEROS, and TESS data in order to fully characterize this planetary system. Results. We find that TOI-4515 b orbits a 1.2 Gyr-old G-star, has an orbital period of Pb = 15.266446 +- 0.000013 days, a mass of Mb = 2.01 +- 0.05 MJ, and a radius of Rb = 1.09 +- 0.04 RJ. We also find an eccentricity of e = 0.46 +- 0.01, placing this planet among the WJs with highly eccentric orbits. As no additional companion has been detected, this high eccentricity might be the consequence of past violent scattering events.

astro-ph.EP↗

arXiv2023

The GAPS programme at TNG. XLV. HI Balmer lines transmission spectroscopy and NLTE atmospheric modelling of the ultra-hot Jupiter KELT-20b/MASCARA-2b

We aim at extracting the transmission spectrum of the HI Balmer lines of the ultra-hot Jupiter (UHJ) KELT-20b/MASCARA-2b from observations and to further compare the results with what obtained through forward modelling accounting for non-local thermodynamic equilibrium (NLTE) effects. We extract the line profiles from six transits obtained with the HARPS-N high-resolution spectrograph attached to the Telescopio Nazionale Galileo telescope. We compute the temperature-pressure (TP) profile employing the helios code in the lower atmosphere and the Cloudy NLTE code in the middle and upper atmosphere. We further use Cloudy to compute the theoretical planetary transmission spectrum in LTE and NLTE for comparison with observations. We detected the Halpha (0.79+/-0.03%; 1.25 Rp), Hbeta (0.52+/-0.03%; 1.17 Rp), and Hgamma (0.39+/-0.06%; 1.13 Rp) lines, while we detected the Hdelta line at almost 4 sigma (0.27+/-0.07%; 1.09 Rp). The models predict an isothermal temperature of about2200 K at pressures >10^-2 bar and of about 7700 K at pressures <10^-8 bar, with a roughly linear temperature rise in between. In the middle and upper atmosphere, the NLTE TP profile is up to about 3000 K hotter than in LTE. The synthetic transmission spectrum derived from the NLTE TP profile is in good agreement with the observed HI Balmer line profiles, validating our obtained atmospheric structure. Instead, the synthetic transmission spectrum derived from the LTE TP profile leads to significantly weaker absorption compared to the observations. Metals appear to be the primary agents leading to the temperature inversion in UHJs and the impact of NLTE effects on them increases the magnitude of the inversion. We find that the impact of NLTE effects on the TP profile of KELT-20b/MASCARA-2b is larger than for the hotter UHJ KELT-9b, and thus NLTE effects might be relevant also for planets cooler than KELT-20b/MASCARA-2b.

astro-ph.EP↗

arXiv2023

The hot Neptune WASP-166 b with ESPRESSO III: A blue-shifted tentative water signal constrains the presence of clouds

With high-resolution spectroscopy we can study exoplanet atmospheres and learn about their chemical composition, temperature profiles, and presence of clouds and winds, mainly in hot, giant planets. State-of-the-art instrumentation is pushing these studies towards smaller exoplanets. Of special interest are the few planets in the 'Neptune desert', a lack of Neptune-size planets in close orbits around their hosts. Here, we assess the presence of water in one such planet, the bloated super-Neptune WASP-166 b, which orbits an F9-type star in a short orbit of 5.4 days. Despite its close-in orbit, WASP-166 b preserved its atmosphere, making it a benchmark target for exoplanet atmosphere studies in the desert. We analyse two transits observed in the visible with ESPRESSO. We clean the spectra from the Earth's telluric absorption via principal component analysis, which is crucial to the search for water in exoplanets. We use a cross-correlation-to-likelihood mapping to simultaneously estimate limits on the abundance of water and the altitude of a cloud layer, which points towards a low water abundance and/or high clouds. We tentatively detect a water signal blue-shifted ~5 km s-1 from the planetary rest frame. Injection and retrieval of model spectra show that a solar-composition, cloud-free atmosphere would be detected at high significance. This is only possible in the visible due to the capabilities of ESPRESSO and the collecting power of the VLT. This work provides further insight on the Neptune desert planet WASP-166 b, which will be observed with JWST.

astro-ph.EP↗

arXiv2022

Detecting H$_2$O with CRIRES+: the case of WASP-20b

Infrared spectroscopy over a wide spectral range and at the highest resolving powers (R>70 000) has proved to be one of the leading technique to unveil the atmospheric composition of dozens of exoplanets. The recently upgraded spectrograph CRIRES instrument at the VLT (CRIRES+) was operative for a first Science Verification in September 2021 and its new capabilities in atmospheric characterisation were ready to be tested. We analysed transmission spectra of the Hot Saturn WASP-20b in the K-band (1981-2394 nm) acquired with CRIRES+, aiming at detecting the signature of H2O and CO. We used Principal Component Analysis to remove the dominant time-dependent contaminating sources such as telluric bands and the stellar spectrum and we extracted the planet spectrum by cross-correlating observations with 1D and 3D synthetic spectra, with no circulation included. We present the tentative detection of molecular absorption from water-vapour at S/N equal to 4.2 and 4.7 by using only-H2O 1D and 3D models, respectively. The peak of the CCF occurred at the same rest-frame velocity for both model types (Vrest=-1 $\pm$ 1 kms$^{-1}$), and at the same projected planet orbital velocity but with different error bands (1D model: KP=131$^{+18}_{-29}$ kms$^{-1}$; 3D: KP=131$^{+23}_{-39}$ kms$^{-1}$). Our results are in agreement with the one expected in literature (132.9 $\pm$ 2.7 kms$^{-1}$). Although sub-optimal observational conditions and issues with pipeline in calibrating and reducing our raw data set, we obtained the first tentative detection of water in the atmosphere of WASP-20b. We suggest a deeper analysis and additional observations to confirm our results and unveil the presence of CO.

astro-ph.EP↗

arXiv2022

The GAPS Programme at TNG. XLI. The climate of KELT-9b revealed with a new approach to high spectral resolution phase curves

[Abridged] We present a novel method to study the thermal emission of exoplanets as a function of orbital phase at very high spectral resolution, and apply it to investigate the climate of the ultra-hot Jupiter KELT-9b. We combine 3 nights of HARPS-N and 2 nights of CARMENES optical spectra, covering orbital phases between quadratures (0.25 < phi < 0.75), when the planet shows its day-side hemisphere with different geometries. We co-add the signal of thousands of FeI lines through cross-correlation, which we map to a likelihood function. We investigate the phase-dependence of: (i) the line depths of FeI, and (ii) their Doppler shifts, by introducing a new method that exploits the very high spectral resolution of our observations. We confirm a previous detection of FeI emission and demonstrate a combined precision of 0.5 km s-1 on the orbital properties of KELT-9b. By studying the phase-resolved Doppler shift of FeI lines, we detect an anomaly in the planet's orbital radial velocity well-fitted with a slightly eccentric orbit (e = 0.016$\pm$0.003, w = 150$^{+13\circ}_{-11},~5\sigma$ preference). However, we argue that such anomaly can be explained by a day-night wind of a few km s-1 blowing neutral iron gas. Additionally, we find that the FeI emission line depths are symmetric around the substellar point within 10 deg ($2\sigma$). We show that these results are qualitatively compatible with predictions from general circulation models for ultra-hot Jupiter planets. Very high-resolution spectroscopy phase curves have the sensitivity to reveal a phase dependence in both the line depths and their Doppler shifts throughout the orbit. They are highly complementary to space-based phase curves obtained with HST and JWST, and open a new window into the still poorly understood climate and atmospheric structure of the hottest planets known.

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