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Barnard's star is a primary target within the ESPRESSO guaranteed time observations (GTO) as it is the second closest neighbour to our Sun after the $\alpha$ Centauri stellar system. We present here a large set of 156 ESPRESSO observations of Barnard's star carried out over four years with the goal of exploring periods of shorter than 50 days, thus including the habitable zone (HZ). Our analysis of ESPRESSO data using Gaussian process (GP) to model stellar activity suggests a long-term activity cycle at 3200d and confirms stellar activity due to rotation at 140d as the dominant source of radial velocity (RV) variations. These results are in agreement with findings based on publicly available HARPS, HARPS-N, and CARMENES data. ESPRESSO RVs do not support the existence of the previously reported candidate planet at 233d. After subtracting the GP model, ESPRESSO RVs reveal several short-period candidate planet signals at periods of 3.15d, 4.12d, 2.34d, and 6.74d. We confirm the 3.15d signal as a sub-Earth mass planet, with a semi-amplitude of $55 \pm 7$cm/s, leading to a planet minimum mass $m_p \sin i$ of $0.37 \pm 0.05$Mearth, which is about three times the mass of Mars. ESPRESSO RVs suggest the possible existence of a candidate system with four sub-Earth mass planets in circular orbits with semi-amplitudes from 20 to 47cm/s, thus corresponding to minimum masses in the range of 0.17-0.32Mearth. The sub-Earth mass planet at $3.1533 \pm 0.0006$d is in a close-to circular orbit with a semi-major axis of $0.0229 \pm 0.0003$AU, thus located inwards from the HZ of Barnard's star, with an equilibrium temperature of 400K. Additional ESPRESSO observations would be required to confirm that the other three candidate signals originate from a compact short-period planet system orbiting Barnard's star inwards from its HZ., Comment: Accepted for publication in Astronomy and Astrophysics

Since 2018, the ESPRESSO spectrograph at the VLT has been hunting for planets in the Southern skies via the RV method. One of its goals is to follow up candidate planets from transit surveys such as the TESS mission, particularly small planets. We analyzed photometry from TESS and ground-based facilities, high-resolution imaging, and RVs from ESPRESSO, HARPS, and HIRES, to confirm and characterize three new planets: TOI-260 b, transiting a late K-dwarf, and TOI-286 b and c, orbiting an early K-dwarf. We also update parameters for the known super-Earth TOI-134 b , hosted by an M-dwarf. TOI-260 b has a $13.475853^{+0.000013}_{-0.000011}$ d period, $4.23 \pm1.60 \mathrm{M_\oplus}$ mass and $1.71\pm0.08\mathrm{R_\oplus}$ radius. For TOI-286 b we find a $4.5117244^{+0.0000031}_{-0.0000027}$ d period, $4.53\pm0.78\mathrm{M_\oplus}$ mass and $1.42\pm0.10\mathrm{R_\oplus}$ radius; for TOI-286 c, a $39.361826^{+0.000070}_{-0.000081}$ d period, $3.72\pm2.22\mathrm{M_\oplus}$ mass and $1.88\pm 0.12\mathrm{R_\oplus}$ radius. For TOI-134 b we obtain a $1.40152604^{+0.00000074}_{-0.00000082}$ d period, $4.07\pm0.45\mathrm{M_\oplus}$ mass, and $1.63\pm0.14\mathrm{R_\oplus}$ radius. Circular models are preferred for all, although for TOI-260 b the eccentricity is not well-constrained. We compute bulk densities and place the planets in the context of composition models. TOI-260 b lies within the radius valley, and is most likely a rocky planet. However, the uncertainty on the eccentricity and thus on the mass renders its composition hard to determine. TOI-286 b and c span the radius valley, with TOI-286 b lying below it and having a likely rocky composition, while TOI-286 c is within the valley, close to the upper border, and probably has a significant water fraction. With our updated parameters for TOI-134 b, we obtain a lower density than previous findings, giving a rocky or Earth-like composition., Comment: 61 pages (of which pp. 24-61 are appendices), 20 figures (main text). Accepted for publication in A&A

The number of super-Earth and mini-Neptune planet discoveries has increased significantly in the last two decades thanks to transit and radial velocity surveys. When it is possible to apply both techniques, we can characterise the internal composition of exoplanets, which in turn provides unique insights on their architecture, formation and evolution. We performed a combined photometric and radial velocity analysis of TOI-238 (TYC 6398-132-1), which has one short-orbit super-Earth planet candidate announced by NASA's TESS team. We aim to confirm its planetary nature using radial velocities taken with the ESPRESSO and HARPS spectrographs, to measure its mass and to detect the presence of other possible planetary companions. We carried out a joint analysis by including Gaussian processes and Keplerian orbits to account for the stellar activity and planetary signals simultaneously. We detected the signal induced by TOI-238 b in the radial velocity time-series, and the presence of a second transiting planet, TOI-238 c, whose signal appears in RV and TESS data. TOI-238 b is a planet with a radius of 1.402$^{+0.084}_{-0.086}$ R$_{\oplus}$ and a mass of 3.40$^{+0.46}_{-0.45}$ M$_{\oplus}$. It orbits at a separation of 0.02118 $\pm$ 0.00038 AU of its host star, with an orbital period of 1.2730988 $\pm$ 0.0000029 days, and has an equilibrium temperature of 1311 $\pm$ 28 K. TOI-238 c has a radius of 2.18$\pm$ 0.18 R$_{\oplus}$ and a mass of 6.7 $\pm$ 1.1 M$_{\oplus}$. It orbits at a separation of 0.0749 $\pm$ 0.0013 AU of its host star, with an orbital period of 8.465652 $\pm$ 0.000031 days, and has an equilibrium temperature of 696 $\pm$ 15 K. The mass and radius of planet b are fully consistent with an Earth-like composition, making it likely a rocky super-Earth. Planet c could be a water-rich planet or a rocky planet with a small H-He atmosphere., Comment: 33 pages, 31 figures, 5 tables. Accepted for publication at A&A

GJ 9827 is a bright, nearby K7V star orbited by two super-Earths and one mini-Neptune on close-in orbits. The system was first discovered using K2 data and then further characterized by other spectroscopic and photometric instruments. Previous literature studies provide several mass measurements for the three planets, however, with large variations and uncertainties. To better constrain the planetary masses, we added high-precision radial velocity measurements from ESPRESSO to published datasets from HARPS, HARPS-N, and HIRES and we performed a Gaussian process analysis combining radial velocity and photometric datasets from K2 and TESS. This method allowed us to model the stellar activity signal and derive precise planetary parameters. We determined planetary masses of $M_b = 4.28_{-0.33}^{+0.35}$ M${_\oplus}$, $M_c = 1.86_{-0.39}^{+0.37}$ M${_\oplus}$, and $M_d = 3.02_{-0.57}^{+0.58}$ M${_\oplus}$, and orbital periods of $1.208974 \pm 0.000001$ days for planet b, $3.648103_{-0.000010}^{+0.000013}$ days for planet c, and $6.201812 \pm 0.000009$ days for planet d. We compared our results to literature values and found that our derived uncertainties for the planetary mass, period, and radial velocity amplitude are smaller than the previously determined uncertainties. We modeled the interior composition of the three planets using the machine-learning-based tool ExoMDN and conclude that GJ 9827 b and c have an Earth-like composition, whereas GJ 9827 d has an hydrogen envelope, which, together with its density, places it in the mini-Neptune regime., Comment: accepted in A&A

We followed-up with ESPRESSO the K0V star HIP 29442 (TOI-469), already known to host a validated sub-Neptune companion TOI-469.01. We aim to verify the planetary nature of TOI-469.01. We modelled radial velocity and photometric time series to measure the dynamical mass, radius, and ephemeris, and to characterise the internal structure and composition of TOI-469.01. We confirmed the planetary nature of TOI-469.01. Thanks to ESPRESSO we discovered two additional close-in companions. We also detected their low signal-to-noise transit signals in the TESS light curve. HIP 29442 is a compact multi-planet system, and the three planets have orbital periods $P_{\rm orb, b}=13.63083\pm0.00003$, $P_{\rm orb, c}=3.53796\pm0.00003$, and $P_{\rm orb, d}=6.42975^{+0.00009}_{-0.00010}$ days, and we measured their masses with high precision: $m_{\rm p, b}=9.6\pm0.8~M_{\oplus}$, $m_{\rm p, c}=4.5\pm0.3~M_{\oplus}$, and $m_{\rm p, d}=5.1\pm0.4~M_{\oplus}$. We measured radii and bulk densities of all the planets (the 3$\sigma$ confidence intervals are shown in parenthesis): $R_{\rm p, b}=3.48^{+0.07 (+0.19)}_{-0.08 (-0.28)} ~R_{\oplus}$ and $\rho_{\rm p, b}=1.3\pm0.2 (0.3) g~cm^{-3}$; $R_{\rm p, c}=1.58^{+0.10 (+0.30)}_{-0.11 (-0.34)}~R_{\oplus}$ and $\rho_{\rm p, c}=6.3^{+1.7 (+6.0)}_{-1.3 (-2.7)} g~cm^{-3}$; $R_{\rm p, d}=1.37\pm0.11^{(+0.32)}_{(-0.43)}~R_{\oplus}$ and $\rho_{\rm p, d}=11.0^{+3.4 (+21.0)}_{-2.4 (-6.3)} g~cm^{-3}$. We used the more conservative 3$\sigma$ confidence intervals for the radii as input to the interior structure modelling. We find that HIP 29442 $b$ appears as a typical sub-Neptune, likely surrounded by a gas layer of pure H-He with a mass of $0.27^{+0.24}_{-0.17} M_{\oplus}$ and a thickness of $1.4\pm0.5 R_{\oplus}$. For the innermost companions HIP 29442 $c$ HIP 29442 $d$, the model supports an Earth-like composition., Comment: Accepted for publication on A&A

Ultra-hot Jupiters, with their high equilibrium temperatures and resolved spectral lines, have emerged as a perfect testbed for new analysis techniques in the study of exoplanet atmospheres. In particular, the resolved sodium doublet as a resonant line has proven a powerful indicator to probe the atmospheric structure over a wide pressure range. We explore an atmospheric origin of the observed blueshifted feature next to the sodium doublet of the ultra-hot Jupiter WASP-121~b, using a partial transit obtained with the 4-UT mode of ESPRESSO. We study its atmospheric dynamics visible across the terminator by splitting the data into mid-transit and egress. We determine that the blueshifted high-velocity absorption component is generated only during the egress part of the transit when a larger fraction of the day side of the planet is visible. For the egress data, MERC retrieves the blueshifted high-velocity absorption component as an equatorial day-to-night side wind across the evening limb, with no zonal winds visible on the morning terminator with weak evidence compared to a model with only vertical winds. For the mid-transit data, the observed line broadening is attributed to a vertical, radial wind. We attribute the equatorial day-to-night side wind over the evening terminator to a localised jet and restrain its existence between the substellar point and up to $10^\circ$ to the terminator in longitude, an opening angle of the jet of at most $60^\circ$ in latitude, and a lower boundary in altitude between [1.08, 1.15] $R_p$. Due to the partial nature of the transit, we cannot make any statements on whether the jet is truly super-rotational and one-sided or part of a symmetric day-to-night side atmospheric wind from the hotspot., Comment: 15 pages, 10 figures, 2 appendixes, accepted for publication in A&A on March 10th, 2023

We present radial velocity follow-up obtained with ESPRESSO of the M-type star LTT 1445A (TOI-455), for which a transiting planet b with an orbital period of~5.4 days was detected by TESS. We report the discovery of a second transiting planet (LTT 1445A c) and a third non-transiting candidate planet (LTT 1445A d) with orbital periods of 3.12 and 24.30 days, respectively. The host star is the main component of a triple M-dwarf system at a distance of 6.9 pc. We used 84 ESPRESSO high-resolution spectra to determine accurate masses of 2.3$\pm$0.3 $\mathrm{M}_\oplus$ and 1.0$\pm$0.2 $\mathrm{M}_\oplus$ for planets b and c and a minimum mass of 2.7$\pm$0.7 $\mathrm{M}_\oplus$ for planet d. Based on its radius of 1.43$\pm0.09$ $\mathrm{R}_\oplus$ as derived from the TESS observations, LTT 1445A b has a lower density than the Earth and may therefore hold a sizeable atmosphere, which makes it a prime target for the James Webb Space Telescope. We used a Bayesian inference approach with the nested sampling algorithm and a set of models to test the robustness of the retrieved physical values of the system. There is a probability of 85$\%$ that the transit of planet c is grazing, which results in a retrieved radius with large uncertainties at 1.60$^{+0.67}_{-0.34}$ $\mathrm{R}_\oplus$. LTT 1445A d orbits the inner boundary of the habitable zone of its host star and could be a prime target for the James Webb Space Telescope., Comment: 31 pages, 20 figures Accepted A&A

High-resolution spectroscopy studies of ultra-hot Jupiters have been key in our understanding of exoplanet atmospheres. Observing into the atmospheres of these giant planets allows for direct constraints on their atmospheric compositions and dynamics while laying the groundwork for new research regarding their formation and evolution environments. Two of the most well-studied ultra-hot Jupiters are WASP-76b and WASP-121b, with multiple detected chemical species and strong signatures of their atmospheric dynamics. We take a new look at these two exceptional ultra-hot Jupiters by reanalyzing the transit observations taken with ESPRESSO at the Very Large Telescope and attempt to detect additional species. To extract the planetary spectra of the two targets, we corrected for the telluric absorption and removed the stellar spectrum contributions. We then exploited new synthetic templates that were specifically designed for ultra-hot Jupiters in combination with the cross-correlation technique to unveil species that remained undetected by previous analyses. We add a novel detection of Ba+ to the known atmospheric compositions of WASP-76b and WASP-121b, the heaviest species detected to date in any exoplanetary atmosphere, with additional new detections of Co and Sr+ and a tentative detection of Ti+ for WASP-121b. We also confirm the presence of Ca+, Cr, Fe, H, Li, Mg, Mn, Na, and V on both WASP-76b and WASP-121b, with the addition of Ca, Fe+, and Ni for the latter. Finally, we also confirm the clear asymmetric absorption feature of Ca+ on WASP-121b, with an excess absorption at the bluer wavelengths and an effective planet radius beyond the Roche lobe. This indicates that the signal may arise from the escape of planetary atmosphere., Comment: 21 pages, 16 figures. Published in A&A Volume 666, October 2022 - Letter to the Editor

Proxima Centauri is the closest star to the Sun. This small, low-mass, mid M dwarf is known to host an Earth-mass exoplanet with an orbital period of 11.2 days within the habitable zone, as well as a long-period planet candidate with an orbital period of close to 5 years. We report on the analysis of a large set of observations taken with the ESPRESSO spectrograph at the VLT aimed at a thorough evaluation of the presence of a third low-mass planetary companion, which started emerging during a previous campaign. Radial velocities (RVs) were calculated using both a cross-correlation function (CCF) and a template matching approach. The RV analysis includes a component to model Proxima's activity using a Gaussian process (GP). We use the CCF's full width at half maximum to help constrain the GP, and we study other simultaneous observables as activity indicators in order to assess the nature of any potential RV signals. We detect a signal at 5.12 $\pm$ 0.04 days with a semi-amplitude of 39 $\pm$ 7 cm/s. The analysis of subsets of the ESPRESSO data, the activity indicators, and chromatic RVs suggest that this signal is not caused by stellar variability but instead by a planetary companion with a minimum mass of 0.26 $\pm$ 0.05 $M_\oplus$ (about twice the mass of Mars) orbiting at 0.029 au from the star. The orbital eccentricity is well constrained and compatible with a circular orbit., Comment: 17 pages, 13 figures

Comparisons of the alignment of exoplanets with a common host star can be used to distinguish among concurrent evolution scenarios. However, multi-planet systems usually host mini-Neptunes and super-Earths, whose size make orbital architecture measurements challenging. We introduce the Rossiter-McLaughlin effect Revolutions technique, which can access spin-orbit angles of small planets by exploiting the full information contained in spectral transit time series. We validated the technique on published HARPS-N data of the mini-Neptune HD3167c, refining its high sky-projected spin-orbit angle (-108.9+5.4-5.5 deg), and we applied it to new ESPRESSO observations of the super-Earth HD3167b, revealing an aligned orbit (-6.6+6.6-7.9 deg). Surprisingly different variations in the contrast of the stellar lines occulted by the planets can be reconciled with a latitudinal dependence of the stellar line shape. In this scenario, a joint fit to both datasets constrains the inclination of the star (111.6+3.1-3.3 deg) and the 3D spin-orbit angles of HD3167b (29.5+7.2-9.4 deg) and HD3167c (107.7+5.1-4.9 deg). The projected spin-orbit angles do not depend on the model for the line contrast variations, and so, with a mutual inclination of 102.3+7.4-8.0 deg, we conclude that the two planets are on perpendicular orbits. This could be explained by HD3167b being strongly coupled to the star and retaining its primordial alignment, whereas HD3167c would have been brought to a nearly polar orbit via secular gravitational interactions with an outer companion. Follow-up observations and dynamical evolution simulations are required to search for this companion and explore this scenario. HD3167b is the smallest exoplanet with a confirmed spectroscopic Rossiter-McLaughlin signal. Our new technique opens the way to determining the orbital architectures of the super-Earth and Earth-sized planet populations., Comment: 20 pages, 19 figures, accepted for publication in A&A (14 September 2021)

The ESPRESSO spectrograph is a new powerful tool to detect and characterize extrasolar planets. Its design allows unprecedented radial velocity precision (down to a few tens of cm/s) and long-term thermo-mechanical stability. We present the first standalone detection of an extrasolar planet by blind radial velocity search using ESPRESSO and aim at showing the power of the instrument in characterizing planetary signals at different periodicities in long time spans. We use 41 ESPRESSO measurements of HD\,22496 within a time span of 895 days with a median photon noise of 18 cm/s. A radial velocity analysis is performed to test the presence of planets in the system and to account for the stellar activity of this K5-K7 main sequence star. For benchmarking and comparison, we attempt the detection with 43 archive HARPS measurements and compare the results yielded by the two datasets. We also use four TESS sectors to search for transits. We find radial velocity variations compatible with a close-in planet with an orbital period of $P=5.09071\pm0.00026$ days when simultaneously accounting for the effects of stellar activity at longer time scales ($P_{\rm rot}=34.99^{+0.58}_{-0.53}$ days). We characterize the physical and orbital properties of the planet and find a minimum mass of $5.57^{+0.73}_{-0.68}$ $\mathrm{M}_{\oplus}$, right in the dichotomic regime between rocky and gaseous planets. Although not transiting according to TESS data, if aligned with the stellar spin axis, the absolute mass of the planet must be below 16 $\mathrm{M}_{\oplus}$. We find no significant evidence for additional signals with semi-amplitudes above 56 cm/s at 95% confidence. With a modest set of radial velocity measurements, ESPRESSO is capable of detecting and characterizing low-mass planets and constrain the presence of planets in the habitable zone of K-dwarfs down to the rocky-mass regime., Comment: Accepted for publication in A&A. 12 pages, 8 figures, 3 tables

The advent of a new generation of radial velocity instruments has allowed us to break the one Earth-mass barrier. We report a new milestone in this context with the detection of the lowest-mass planet measured so far using radial velocities: L 98-59 b, a rocky planet with half the mass of Venus. It is part of a system composed of three known transiting terrestrial planets (planets b to d). We announce the discovery of a fourth nontransiting planet with a minimum mass of 3.06_{-0.37}^{+0.33} MEarth and an orbital period of 12.796_{-0.019}^{+0.020} days and report indications for the presence of a fifth nontransiting terrestrial planet. With a minimum mass of 2.46_{-0.82}^{+0.66} MEarth and an orbital period 23.15_{-0.17}^{+0.60} days, this planet, if confirmed, would sit in the middle of the habitable zone of the L 98-59 system. L 98-59 is a bright M dwarf located 10.6 pc away. Positioned at the border of the continuous viewing zone of the James Webb Space Telescope, this system is destined to become a corner stone for comparative exoplanetology of terrestrial planets. The three transiting planets have transmission spectrum metrics ranging from 49 to 255, which makes them prime targets for an atmospheric characterization with the James Webb Space Telescope, the Hubble Space Telescope, Ariel, or ground-based facilities such as NIRPS or ESPRESSO. With an equilibrium temperature ranging from 416 to 627 K, they offer a unique opportunity to study the diversity of warm terrestrial planets. L 98-59 b and c have densities of 3.6_{-1.5}^{+1.4} and 4.57_{-0.85}^{+0.77} g.cm^{-3}, respectively, and have very similar bulk compositions with a small iron core that represents only 12 to 14 % of the total mass, and a small amount of water. However, with a density of 2.95_{-0.51}^{+0.79} g.cm^{-3} and despite a similar core mass fraction, up to 30 % of the mass of L 98-59 d might be water., Comment: 38 pages, 23 figures, Accepted for publication in Astronomy & Astrophysics

Despite swift progress in the characterisation of exoplanet atmospheres in composition and structure, the study of atmospheric dynamics has not progressed at the same speed. While theoretical models have been developed to describe the lower layers of the atmosphere and, disconnected, the exosphere, little is known about the intermediate layers up to the thermosphere. We aim to provide a clearer picture of atmospheric dynamics for the class of ultra hot Jupiters, highly-irradiated gas giants, on the example of WASP-76~b. We analysed two datasets jointly, obtained with the HARPS and ESPRESSO spectrographs, to interpret the resolved planetary sodium doublet. We then applied an updated version of the MERC code, with added planetary rotation, also provides the possibility to model the latitude dependence of the wind patterns. We retrieve the highest Bayesian evidence for an isothermal atmosphere, interpreted as a mean temperature of $3389\pm227$ K, a uniform day-to-night side wind of $5.5^{+1.4}_{-2.0}\,$ km/s in the lower atmosphere with a vertical wind in the upper atmosphere of $22.7^{+4.9}_{-4.1}\,$ km/s, switching atmospheric wind patterns at $10^{-3}$ bar above the reference surface pressure ($10$ bar). Our results for WASP-76~b are compatible with previous studies of the lower atmospheric dynamics of WASP-76~b and other ultra hot Jupiters. They highlight the need for vertical winds in the intermediate atmosphere above the layers probed by global circulation model studies to explain the line broadening of the sodium doublet in this planet. This work demonstrates the capability of exploiting the resolved spectral line shapes to observationally constrain possible wind patterns in exoplanet atmospheres, an invaluable input to more sophisticated 3D atmospheric models in the future., Comment: 17 pages, 20 figures, submitted to A&A 15.Feb.2021, accepted for publication in A&A 20.Jul.2021

[Abridged] We exploit the extreme radial velocity (RV) precision of the ultra-stable echelle spectrograph ESPRESSO on the VLT to unveil the physical properties of the transiting sub-Neptune TOI-130 b, uncovered by TESS orbiting the nearby, bright, late F-type star HD 5278 (TOI-130) with a period $P_{\rm b}=14.3$. We use 43 ESPRESSO high-resolution spectra and broad-band photometry information to derive accurate stellar atmospheric and physical parameters of HD 5278. We exploit the TESS light curve (LC) and spectroscopic diagnostics to gauge the impact of stellar activity on the ESPRESSO RVs. We perform a joint ESPRESSO RVs + TESS LC analysis using fully Bayesian frameworks to determine the system parameters. The updated stellar parameters of HD 5278 are T$_\mathrm{eff}=6203\pm64$ K, $\log g =4.50\pm0.11$ dex, [Fe/H]=$-0.12\pm0.04$ dex, M$_\star=1.126_{-0.035}^{+0.036}$ M$_\odot$ and R$_\star=1.194_{-0.016}^{+0.017}$ R$_\odot$. We determine HD 5278 b's mass and radius to be $M_{\rm b} = 7.8_{-1.4}^{+1.5}$ M$_\oplus$ and $R_{\rm b} = 2.45\pm0.05$ R$_\oplus$. The derived mean density, $\varrho_{\rm b} = 2.9_{-0.5}^{+0.6}$ g cm$^{-3}$, is consistent with a bulk composition with a substantial ($\sim30\%$) water mass fraction and a gas envelope comprising $\sim17\%$ of the measured radius. Given the host brightness and irradiation levels, HD 5278 b is one of the best targets orbiting G-F primaries for follow-up atmospheric characterization measurements with HST and JWST. We discover a second, non-transiting companion in the system, with a period $P_{\rm c}=40.87_{-0.17}^{+0.18}$ days and a minimum mass $M_{\rm c}\sin i_{\rm c} =18.4_{-1.9}^{+1.8}$ M$_\oplus$. We study emerging trends in the growing population of transiting sub-Neptunes, and provide statistical evidence for a low occurrence of close-in, $10-15$ M$_\oplus$ companions around G-F primaries with $T_\mathrm{eff}\gtrsim5500$ K.

Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at a 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from 1.152(-0.070/+0.073) to 2.87(-0.13/+0.14) Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02(+0.28/-0.23) to 0.177(+0.055/-0.061) times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes.

We observed two transits of the iconic gas giant HD 209458b between 380 and 780 nm, using the high-resolution ESPRESSO spectrograph. The derived planetary transmission spectrum exhibits features at all wavelengths where the parent star shows strong absorption lines, for example, NaI, MgI, FeI, FeII, CaI, VI, H$\alpha$, and KI. We interpreted these features as the signature of the deformation of the stellar line profiles due to the Rossiter-McLaughlin effect, combined with the centre-to-limb effects on the stellar surface, which is in agreement with similar reports recently presented in the literature. We also searched for species that might be present in the planetary atmosphere but not in the stellar spectra, such as TiO and VO, and obtained a negative result. Thus, we find no evidence of any planetary absorption, including previously reported NaI, in the atmosphere of HD 209458b. The high signal-to-noise ratio in the transmission spectrum allows us to compare the modelled deformation of the stellar lines in assuming different one-dimensional stellar atmospheric models. We conclude that the differences among various models and observations remain within the precision limits of the data. However, the transmission light curves are better explained when the centre-to-limb variation is not included in the computation and only the Rossiter-McLaughlin deformation is considered. This demonstrates that ESPRESSO is currently the best facility for spatially resolving the stellar surface spectrum in the optical range using transit observations and carrying out empirical validations of stellar models., Comment: 21 pages, 19 figures. Accepted

Aims. We report on ESPRESSO high-resolution transmission spectroscopic observations of two primary transits of the highly-irradiated, ultra-hot Jupiter-size planet WASP-76b. We investigate the presence of several key atomic and molecular features of interest that may reveal the atmospheric properties of the planet. Methods. We extracted two transmission spectra of WASP-76b with R approx 140,000 using a procedure that allowed us to process the full ESPRESSO wavelength range (3800-7880 A) simultaneously. We observed that at a high signal-to-noise ratio, the continuum of ESPRESSO spectra shows wiggles that are likely caused by an interference pattern outside the spectrograph. To search for the planetary features, we visually analysed the extracted transmission spectra and cross-correlated the observations against theoretical spectra of different atomic and molecular species. Results. The following atomic features are detected: Li I, Na I, Mg I, Ca II, Mn I, K I, and Fe I. All are detected with a confidence level between 9.2 sigma (Na I) and 2.8 sigma (Mg I). We did not detect the following species: Ti I, Cr I, Ni I, TiO, VO, and ZrO. We impose the following 1 sigma upper limits on their detectability: 60, 77, 122, 6, 8, and 8 ppm, respectively. Conclusions. We report the detection of Li I on WASP-76b for the first time. In addition, we found the presence of Na I and Fe I as previously reported in the literature. We show that the procedure employed in this work can detect features down to the level of ~ 0.1 % in the transmission spectrum and ~ 10 ppm by means of a cross-correlation method. We discuss the presence of neutral and singly ionised features in the atmosphere of WASP-76b., Comment: 20 pages, 19 figures, accepted for publication in Astronomy and Astrophysics

The detection and characterization of exoplanet atmospheres is currently one of the main drivers pushing the development of new observing facilities. In this context, high-resolution spectrographs are {proving} their potential and showing that high-resolution spectroscopy will be paramount in this field. We aim to make use of ESPRESSO high-resolution spectra, which cover two transits of HD209458b, to probe the broadband transmission optical spectrum of the planet. We applied the chromatic Rossiter-McLaughin method to derive the transmission spectrum of HD209458b. We compared the results with previous HST observations and with synthetic spectra. We recover a transmission spectrum of HD209458b similar to the one obtained with HST data. The models suggest that the observed signal can be explained by only Na, only TiO, or both Na and TiO, even though none is fully capable of explaining our observed transmission spectrum. Extra absorbers may be needed to explain the full dataset, though modeling approximations and observational errors can also be responsible for the observed mismatch. Using the chromatic Rossiter-McLaughlin technique, ESPRESSO is able to provide broadband transmission spectra of exoplanets from the ground, in conjunction with space-based facilities, opening good perspectives for similar studies of other planets., Comment: Accepted for publication in A&A

WASP-121b is one of the most studied Ultra-hot Jupiters: many recent analyses of its atmosphere report interesting features at different wavelength ranges. In this paper we analyze one transit of WASP-121b acquired with the high-resolution spectrograph ESPRESSO at VLT in 1-telescope mode, and one partial transit taken during the commissioning of the instrument in 4-telescope mode. We investigate the anomalous in-transit radial velocity curve and study the transmission spectrum of the planet. By analysing the in-transit radial velocities we were able to infer the presence of the atmospheric Rossiter-McLaughlin effect. We measured the height of the planetary atmospheric layer that correlates with the stellar mask (mainly Fe) to be 1.052$\pm$0.015 Rp and we also confirmed the blueshift of the planetary atmosphere. By examining the planetary absorption signal on the stellar cross-correlation functions we confirmed the presence of a temporal variation of its blueshift during transit, which could be investigated spectrum-by-spectrum. We detected significant absorption in the transmission spectrum for Na, H, K, Li, CaII, Mg, and we certified their planetary nature by using the 2D tomographic technique. Particularly remarkable is the detection of Li, with a line contrast of $\sim$0.2% detected at the 6$\sigma$ level. With the cross-correlation technique we confirmed the presence of FeI, FeII, CrI and VI. H$\alpha$ and CaII are present up to very high altitudes in the atmosphere ($\sim$1.44 Rp and $\sim$2 Rp, respectively), and also extend beyond the transit-equivalent Roche lobe radius of the planet. These layers of the atmosphere have a large line broadening that is not compatible with being caused by the tidally-locked rotation of the planet alone, and could arise from vertical winds or high-altitude jets in the evaporating atmosphere., Comment: 15 pages, 19 figures. Accepted for publication in A&A

The study of exoplanet atmospheres is essential to understand the formation, evolution and composition of exoplanets. The transmission spectroscopy technique is playing a significant role in this domain. In particular, the combination of state-of-the-art spectrographs at low- and high-spectral resolution is key to our understanding of atmospheric structure and composition. Two transits of the close-in sub Saturn-mass planet,WASP-127b, have been observed with ESPRESSO in the frame of the Guaranteed Time Observations Consortium. Transit observations allow us to study simultaneously the system architecture and the exoplanet atmosphere. We found that this planet is orbiting its slowly rotating host star (veq sin(i)=0.53+/-0.07 km/s) on a retrograde misaligned orbit (lambda=-128.41+/-5.60 deg). We detected the sodium line core at the 9-sigma confidence level with an excess absorption of 0.3+/-0.04%, a blueshift of 2.7+/-0.79 km/s and a FWHM of 15.18+/-1.75 km/s. However, we did not detect the presence of other atomic species but set upper-limits of only few scale heights. Finally, we put a 3-sigma upper limit, to the average depth of the 1600 strongest water lines at equilibrium temperature in the visible band, of 38 ppm. This constrains the cloud-deck pressure between 0.3 and 0.5 mbar by combining our data with low-resolution data in the near-infrared and models computed for this planet. To conclude, WASP-127b, with an age of about 10 Gyr, is an unexpected exoplanet by its orbital architecture but also by the small extension of its sodium atmosphere (~7 scale heights). ESPRESSO allows us to take a step forward in the detection of weak signals, thus bringing strong constraints on the presence of clouds in exoplanet atmospheres. The framework proposed in this work can be applied to search for molecular species and study cloud-decks in other exoplanets., Comment: Accepted in A&A, 19 pages, 20 figures

This paper reports on the detailed characterisation of the K2-111 planetary system with K2, WASP, and ASAS-SN photometry as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved ($\log g=4.17$), iron-poor ([Fe/H]$=-0.46$), but alpha-enhanced ([$\alpha$/Fe]$=0.27$), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT shows that the transiting planet, K2-111b, orbits with a period $P_b=5.3518\pm0.0004$ d, and has a planet radius of $1.82^{+0.11}_{-0.09}$ R$_\oplus$ and a mass of $5.29^{+0.76}_{-0.77}$ M$_\oplus$, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111c, with an orbital period of $15.6785\pm 0.0064$ days, orbiting in near-3:1 mean-motion resonance with the transiting planet, and a minimum planet mass of $11.3\pm1.1$ M$_\oplus$. Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters., Comment: Accepted for publication in MNRAS on 28 Sept 2020. Paper is 18 pages with an additional 12 pages of supplementary material. Data is available at https://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/MNRAS/499/5004

ESPRESSO is the new high-resolution spectrograph of ESO's Very-Large Telescope (VLT). It was designed for ultra-high radial-velocity precision and extreme spectral fidelity with the aim of performing exoplanet research and fundamental astrophysical experiments with unprecedented precision and accuracy. It is able to observe with any of the four Unit Telescopes (UT) of the VLT at a spectral resolving power of 140,000 or 190,000 over the 378.2 to 788.7 nm wavelength range, or with all UTs together, turning the VLT into a 16-m diameter equivalent telescope in terms of collecting area, while still providing a resolving power of 70,000. We provide a general description of the ESPRESSO instrument, report on the actual on-sky performance, and present our Guaranteed-Time Observation (GTO) program with its first results. ESPRESSO was installed on the Paranal Observatory in fall 2017. Commissioning (on-sky testing) was conducted between December 2017 and September 2018. The instrument saw its official start of operations on October 1st, 2018, but improvements to the instrument and re-commissioning runs were conducted until July 2019. The measured overall optical throughput of ESPRESSO at 550 nm and a seeing of 0.65 arcsec exceeds the 10% mark under nominal astro-climatic conditions. We demonstrate a radial-velocity precision of better than 25 cm/s during one night and 50 cm/s over several months. These values being limited by photon noise and stellar jitter show that the performanceis compatible with an instrumental precision of 10 cm/s. No difference has been measured across the UTs neither in throughput nor RV precision. The combination of the large collecting telescope area with the efficiency and the exquisite spectral fidelity of ESPRESSO opens a new parameter space in RV measurements, the study of planetary atmospheres, fundamental constants, stellar characterisation and many other fields., Comment: 26 pages, 28 figures

The bright star $\pi$ Men was chosen as the first target for a radial velocity follow-up to test the performance of ESPRESSO, the new high-resolution spectrograph at the ESO's Very-Large Telescope (VLT). The star hosts a multi-planet system (a transiting 4 M$_\oplus$ planet at $\sim$0.07 au, and a sub-stellar companion on a $\sim$2100-day eccentric orbit) which is particularly appealing for a precise multi-technique characterization. With the new ESPRESSO observations, that cover a time span of 200 days, we aim to improve the precision and accuracy of the planet parameters and search for additional low-mass companions. We also take advantage of new photometric transits of $\pi$ Men c observed by TESS over a time span that overlaps with that of the ESPRESSO follow-up campaign. We analyse the enlarged spectroscopic and photometric datasets and compare the results to those in the literature. We further characterize the system by means of absolute astrometry with Hipparcos and Gaia. We used the spectra of ESPRESSO for an independent determination of the stellar fundamental parameters. We present a precise characterization of the planetary system around $\pi$ Men. The ESPRESSO radial velocities alone (with typical uncertainty of 10 cm/s) allow for a precise retrieval of the Doppler signal induced by $\pi$ Men c. The residuals show an RMS of 1.2 m/s, and we can exclude companions with a minimum mass less than $\sim$2 M$_\oplus$ within the orbit of $\pi$ Men c). We improve the ephemeris of $\pi$ Men c using 18 additional TESS transits, and in combination with the astrometric measurements, we determine the inclination of the orbital plane of $\pi$ Men b with high precision ($i_{b}=45.8^{+1.4}_{-1.1}$ deg). This leads to the precise measurement of its absolute mass $m_{b}=14.1^{+0.5}_{-0.4}$ M$_{Jup}$, and shows that the planetary orbital planes are highly misaligned., Comment: Accepted for publication on A&A

We characterized the transiting planetary system orbiting the G2V star K2-38 using the new-generation echelle spectrograph ESPRESSO. We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets. Using 43 ESPRESSO high-precision radial velocity measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a MCMC analysis, significantly improving their mass measurements. Using ESPRESSO spectra, we derived the stellar parameters, $T_{\rm eff}$=5731$\pm$66, $\log g$=4.38$\pm$0.11~dex, and $[Fe/H]$=0.26$\pm$0.05~dex, and thus the mass and radius of K2-38, $M_{\star}$=1.03 $^{+0.04}_{-0.02}$~M$_{\oplus}$ and $R_{\star}$=1.06 $^{+0.09}_{-0.06}$~R$_{\oplus}$. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with $R_{\rm P}$=1.54$\pm$0.14~R$_{\rm \oplus}$ and $M_{\rm p}$=7.3$^{+1.1}_{-1.0}$~M$_{\oplus}$, and K2-38c as a sub-Neptune with $R_{\rm P}$=2.29$\pm$0.26~R$_{\rm \oplus}$ and $M_{\rm p}$=8.3$^{+1.3}_{-1.3}$~M$_{\oplus}$. We derived a mean density of $\rho_{\rm p}$=11.0$^{+4.1}_{-2.8}$~g cm$^{-3}$ for K2-38b and $\rho_{\rm p}$=3.8$^{+1.8}_{-1.1}$~g~cm$^{-3}$ for K2-38c, confirming K2-38b as one of the densest planets known to date. The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky model with a H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the radial velocity time-series whose origin could be linked to a 0.25-3~M$_{\rm J}$ planet or stellar activity., Comment: 16 pages, 14 figures

We aim to confirm the presence of Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refine the planetary parameters taking advantage of its improved precision. We analysed 63 spectroscopic ESPRESSO observations of Proxima taken during 2019. We obtained radial velocity measurements with a typical radial velocity photon noise of 26 cm/s. We ran a joint MCMC analysis on the time series of the radial velocity and full-width half maximum of the cross-correlation function to model the planetary and stellar signals present in the data, applying Gaussian process regression to deal with stellar activity. We confirm the presence of Proxima b independently in the ESPRESSO data. The ESPRESSO data on its own shows Proxima b at a period of 11.218 $\pm$ 0.029 days, with a minimum mass of 1.29 $\pm$ 0.13 Me. In the combined dataset we measure a period of 11.18427 $\pm$ 0.00070 days with a minimum mass of 1.173 $\pm$ 0.086 Me. We find no evidence of stellar activity as a potential cause for the 11.2 days signal. We find some evidence for the presence of a second short-period signal, at 5.15 days with a semi-amplitude of merely 40 cm/s. If caused by a planetary companion, it would correspond to a minimum mass of 0.29 $\pm$ 0.08 Me. We find that the FWHM of the CCF can be used as a proxy for the brightness changes and that its gradient with time can be used to successfully detrend the radial velocity data from part of the influence of stellar activity. The activity-induced radial velocity signal in the ESPRESSO data shows a trend in amplitude towards redder wavelengths. Velocities measured using the red end of the spectrograph are less affected by activity, suggesting that the stellar activity is spot-dominated. The data collected excludes the presence of extra companions with masses above 0.6 Me at periods shorter than 50 days., Comment: 25 pages, 26 figures

Ultra-hot giant exoplanets receive thousands of times Earth's insolation. Their high-temperature atmospheres (>2,000 K) are ideal laboratories for studying extreme planetary climates and chemistry. Daysides are predicted to be cloud-free, dominated by atomic species and substantially hotter than nightsides. Atoms are expected to recombine into molecules over the nightside, resulting in different day-night chemistry. While metallic elements and a large temperature contrast have been observed, no chemical gradient has been measured across the surface of such an exoplanet. Different atmospheric chemistry between the day-to-night ("evening") and night-to-day ("morning") terminators could, however, be revealed as an asymmetric absorption signature during transit. Here, we report the detection of an asymmetric atmospheric signature in the ultra-hot exoplanet WASP-76b. We spectrally and temporally resolve this signature thanks to the combination of high-dispersion spectroscopy with a large photon-collecting area. The absorption signal, attributed to neutral iron, is blueshifted by -11+/-0.7 km s-1 on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside. In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. Iron must thus condense during its journey across the nightside., Comment: Published in Nature (Accepted on 24 January 2020.) 33 pages, 11 figures, 3 tables

One of the main scientific drivers for ESPRESSO,\'Echelle SPectrograph, is the detection and characterization of Earth-class exoplanets. With this goal in mind, the ESPRESSO Guaranteed Time Observations (GTO) Catalog identifies the best target stars for a blind search for the radial velocity (RV) signals caused by Earth-class exoplanets. Using the most complete stellar catalogs available, we screened for the most suitable G, K, and M dwarf stars for the detection of Earth-class exoplanets with ESPRESSO. For most of the stars, we then gathered high-resolution spectra from new observations or from archival data. We used these spectra to spectroscopically investigate the existence of any stellar binaries, both bound or background stars. We derived the activity level using chromospheric activity indexes using $log(R'_{HK})$, as well as the projected rotational velocity $\textit{v sin i}$. For the cases where planet companions are already known, we also looked at the possibility that additional planets may exist in the host's habitable zone using dynamical arguments. We estimated the spectroscopic contamination level, $\textit{v sin i}$, activity, stellar parameters and chemical abundances for 249 of the most promising targets. Using these data, we selected 45 stars that match our criteria for detectability of a planet like Earth. The stars presented and discussed in this paper constitute the ESPRESSO GTO catalog for the RV blind search for Earth-class planets. They can also be used for any other work requiring a detailed spectroscopic characterization of stars in the solar neighborhood., Comment: Corrected a typo in references. Corrected typo in table B.2

Ice sintering is a form of metamorphism that drives the microstructural evolution of an aggregate of grains through surface and volume diffusion. This leads to an increase in the grain-to-grain contact area ("neck") and density of the aggregate over time, resulting in the evolution of its strength, porosity, thermal conductivity, and other properties. This process plays an important role in the evolution of icy planetary surfaces, though its rate and nature are not well constrained. In this study, we explore the model of Swinkels and Ashby (1981), and assess the extent to which it can be used to quantify sintering timescales for water ice. We compare predicted neck growth rates to new and historical observations of ice sintering, and find agreement to some studies at the order of magnitude level. First-order estimates of neck growth timescales on planetary surfaces show that ice may undergo significant modification over geologic timescales, even in the outer solar system. Densification occurs over much longer timescales, suggesting some surfaces may develop cohesive, but porous, crusts. Sintering rates are extremely sensitive to temperature and grain size, occurring faster in warmer aggregates of smaller grains. This suggests that the microstructural evolution of ices may vary not only throughout the solar system, but also spatially across the surface and in the near-surface of a given body. Our experimental observations of complex grain growth and mass redistribution in ice aggregates point to components of the model that may benefit from improvement, and areas where additional laboratory studies are needed., Comment: Main Text 48 pages (17 figures, 8 tables, 2 appendices), 75 pages incl. Supplemental Information, Journal of Geophysical Research: Planets

ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) is a VLT ultra-stable high resolution spectrograph installed at ESO's Paranal Observatory in Chile at the end of 2017 and that started regular operations in October 2018. The spectrograph is located at the VLT Combined-Coud\'e Laboratory and is able to operate with one or (simultaneously) four 8.2m Unit Telescopes (UTs) through four optical Coud\'e trains. Combining efficiency and extreme spectroscopic precision, ESPRESSO has demonstrated to gain about two magnitudes with respect to its predecessor HARPS. ESPRESSO has improved the instrumental radial-velocity precision getting close to the aimed 10 cm/s level, thus opening the possibility to explore new frontiers in the search for Earth-mass exoplanets in the habitable zone of quiet, nearby G to M-dwarfs. ESPRESSO will be certainly an important development step towards high-precision ultra-stable spectrographs on the next generation of giant telescopes such as the ELT., Comment: To be published in: Handbook of Exoplanets, 2nd Edition, Hans Deeg and Juan Antonio Belmonte (Eds. in Chief), Springer International Publishing AG, part of Springer Nature

With the manuscript of the Sidereus Nuncius preserved at the Biblioteca Nazionale of Florence are included 7 watercolors of the Moon painted by Galileo himself. We suggest that some of them, and in particular the drawing of the 30 Nov 1609 of the very first Moon's observations, illustrate the phenomenon of the Earthshine of the Moon, which was discussed in some detail in the Sidereus Nuncius to provide evidence of the similarity of Earth to other celestial bodies. The watercolors were used as models for the engraving of the Moon in the Sidereus but, surprisingly, the secondary light had not been reproduced. Galileo may have decided for the inclusion of the passage on the Earthshine only at a very late stage of the editorial process. Galileo's hesitation shows how contentious was this issue already recognized as a possible discriminant between the different systems of the world.

This work investigates the macroscopic thermomechanical behavior of lunar boulders by modeling their response to diurnal thermal forcing. Our results reveal a bimodal, spatiotemporally-complex stress response. During sunrise, stresses occur in the boulders' interiors that are associated with large-scale temperature gradients developed due to overnight cooling. During sunset, stresses occur at the boulders' exteriors due to the cooling and contraction of the surface. Both kinds of stresses are on the order of 10 MPa in 1 m boulders and decrease for smaller diameters, suggesting that larger boulders break down more quickly. Boulders <30 cm exhibit a weak response to thermal forcing, suggesting a threshold below which crack propagation may not occur. Boulders of any size buried by regolith are shielded from thermal breakdown. As boulders increase in size (>1 m), stresses increase to several 10s of MPa as the behavior of their surfaces approaches that of an infinite halfspace. As the thermal wave loses contact with the boulder interior, stresses become limited to the near-surface. This suggests that the survival time of a boulder is not only controlled by the amplitude of induced stress, but also by its diameter as compared to the diurnal skin depth. While stresses on the order of 10 MPa are enough to drive crack propagation in terrestrial environments, crack propagation rates in vacuum are not well constrained. We explore the relationship between boulder size, stress, and the direction of crack propagation, and discuss the implications for the relative breakdown rates and estimated lifetimes of boulders on airless body surfaces., Comment: 31 pages, 12 figures

In the framework of the GAPS project, we are conducting an observational programme aimed at the determination of the orbital obliquity of known transiting exoplanets. The targets are selected to probe the obliquity against a wide range of stellar and planetary physical parameters. We exploit high-precision radial velocity (RV) measurements, delivered by the HARPS-N spectrograph at the 3.6m Telescopio Nazionale Galileo, to measure the Rossiter-McLaughlin (RM) effect in RV time-series bracketing planet transits, and to refine the orbital parameters determinations with out-of-transit RV data. We also analyse new transit light curves obtained with several 1-2m class telescopes to better constrain the physical fundamental parameters of the planets and parent stars. We report here on new transit spectroscopic observations for three very massive close-in giant planets: WASP43b, HATP20b and Qatar2b orbiting dwarf K-type stars with effective temperature well below 5000K. We find lambda = 3.5pm6.8 deg for WASP43b and lambda = -8.0pm6.9 deg for HATP20b, while for Qatar2, our faintest target, the RM effect is only marginally detected, though our best-fit value lambda = 15pm20 deg is in agreement with a previous determination. In combination with stellar rotational periods derived photometrically, we estimate the true spin-orbit angle, finding that WASP43b is aligned while the orbit of HATP20b presents a small but significant obliquity (Psi=36 _{-12}^{+10} deg). By analyzing the CaII H&K chromospheric emission lines for HATP20 and WASP43, we find evidence for an enhanced level of stellar activity which is possibly induced by star-planet interactions.

Bright features have been recently discovered by Dawn on Ceres, which extend previous photometric and Space Telescope observations. These features should produce distortions of the line profiles of the reflected solar spectrum and therefore an apparent radial velocity variation modulated by the rotation of the dwarf planet. Here we report on two sequences of observations of Ceres performed in the nights of 31 July, 26-27 August 2015 by means of the high-precision HARPS spectrograph at the 3.6-m La Silla ESO telescope. The observations revealed a quite complex behaviour which likely combines a radial velocity modulation due to the rotation with an amplitude of approx +/- 6 m/s and an unexpected diurnal effect. The latter changes imply changes in the albedo of Occator's bright features due to the blaze produced by the exposure to solar radiation. The short-term variability of Ceres' albedo is on timescales ranging from hours to months and can both be confirmed and followed by means of dedicated radial velocity observations., Comment: 5 pag, 1fig, two tables, MNRAS Letters 2016

Stellar radial velocities play a fundamental role in the discovery of extrasolar planets and the measurement of their physical parameters as well as in the study of stellar physical properties. We investigate the impact of the solar activity on the radial velocity of the Sun using the HARPS spectrograph to obtain measurements that can be directly compared with those acquired in the extrasolar planet search programs. We use the Moon, the Galilean satellites, and several asteroids as reflectors to measure the radial velocity of the Sun as a star and correlate it with disc-integrated chromospheric and magnetic indexes of solar activity that are similar to stellar activity indexes. We discuss in detail the systematic effects that affect our measurements and the methods to account for them. We find that the radial velocity of the Sun as a star is positively correlated with the level of its chromospheric activity at about 95 percent significance level. The amplitude of the long-term variation measured in the 2006-2014 period is 4.98 \pm 1.44 m/s, in good agreement with model predictions. The standard deviation of the residuals obtained by subtracting a linear best fit is 2.82 m/s and is due to the rotation of the reflecting bodies and the intrinsic variability of the Sun on timescales shorter than the activity cycle. A correlation with a lower significance is detected between the radial velocity and the mean absolute value of the line-of-sight photospheric magnetic field flux density. Our results confirm similar correlations found in other late-type main-sequence stars and provide support to the predictions of radial velocity variations induced by stellar activity based on current models., Comment: 11 pages, 7 figures, 2 tables, 1 Appendix; accepted by Astronomy and Astrophysics

We report on a multi-wavelength observational campaign which followed the Earth's transit on the Sun as seen from Jupiter on 5 Jan the 2014. Simultaneous observations of Jupiter's moons Europa and Ganymede obtained with HARPS from La Silla, Chile, and HARPS-N from La Palma, Canary Islands, were performed to measure the Rossiter-McLaughlin effect due to the Earth's passage using the same technique successfully adopted for the 2012 Venus Transit (Molaro et al 2013). The expected modulation in radial velocities was of about 20 cm/s but an anomalous drift as large as 38 m/s, i.e. more than two orders of magnitude higher and opposite in sign, was detected instead. The consistent behaviour of the two spectrographs rules out instrumental origin of the radial velocity drift and BiSON observations rule out the possible dependence on the Sun's magnetic activity. We suggest that this anomaly is produced by the Opposition Surge on Europa's icy surface, which amplifies the intensity of the solar radiation from a portion of the solar surface centered around the crossing Earth which can then be observed as a a sort of inverse Rossiter-McLaughling effect. in fact, a simplified model of this effect can explain in detail most features of the observed radial velocity anomalies, namely the extensions before and after the transit, the small differences between the two observatories and the presence of a secondary peak closer to Earth passage. This phenomenon, observed here for the first time, should be observed every time similar Earth alignments occur with rocky bodies without atmospheres. We predict it should be observed again during the next conjunction of Earth and Jupiter in 2026., Comment: 9 pages, 7 figures

Minor bodies of the solar system can be used to measure the spectrum of the Sun as a star by observing sunlight reflected by their surfaces. To perform an accurate measurement of the radial velocity of the Sun as a star by this method, it is necessary to take into account the Doppler shifts introduced by the motion of the reflecting body. Here we discuss the effect of its rotation. It gives a vanishing contribution only when the inclinations of the body rotation axis to the directions of the Sun and of the Earth observer are the same. When this is not the case, the perturbation of the radial velocity does not vanish and can reach up to about 2.4 m/s for an asteroid such as 2 Pallas that has an inclination of the spin axis to the plane of the ecliptic of about 30 degrees. We introduce a geometric model to compute the perturbation in the case of a uniformly reflecting body of spherical or triaxial ellipsoidal shape and provide general results to easily estimate the magnitude of the effect., Comment: 14 pages, 5 figures, 3 tables, accepted by Experimental Astronomy

Thermomechanical processes such as fatigue and shock have been suggested to cause and contribute to rock breakdown on Earth, and on other planetary bodies, particularly airless bodies in the inner solar system. In this study, we modeled grain-scale stresses induced by diurnal temperature variations on simple microstructures made of pyroxene and plagioclase on various solar system bodies. We found that a heterogeneous microstructure on the Moon experiences peak tensile stresses on the order of 100 MPa. The stresses induced are controlled by the coefficient of thermal expansion and Young's modulus of the mineral constituents, and the average stress within the microstructure is determined by relative volume of each mineral. Amplification of stresses occurs at surface-parallel boundaries between adjacent mineral grains and at the tips of pore spaces. We also found that microscopic spatial and temporal surface temperature gradients do not correlate with high stresses, making them inappropriate proxies for investigating microcrack propagation. Although these results provide very strong evidence for the significance of thermomechanical processes on airless bodies, more work is needed to quantify crack propagation and rock breakdown rates., Comment: 34 pages, 12 figures

The acronym ESPRESSO stems for Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations; this instrument will be the next VLT high resolution spectrograph. The spectrograph will be installed at the Combined-Coud\'e Laboratory of the VLT and linked to the four 8.2 m Unit Telescopes (UT) through four optical Coud\'e trains. ESPRESSO will combine efficiency and extreme spectroscopic precision. ESPRESSO is foreseen to achieve a gain of two magnitudes with respect to its predecessor HARPS, and to improve the instrumental radial-velocity precision to reach the 10 cm/s level. It can be operated either with a single UT or with up to four UTs, enabling an additional gain in the latter mode. The incoherent combination of four telescopes and the extreme precision requirements called for many innovative design solutions while ensuring the technical heritage of the successful HARPS experience. ESPRESSO will allow to explore new frontiers in most domains of astrophysics that require precision and sensitivity. The main scientific drivers are the search and characterization of rocky exoplanets in the habitable zone of quiet, nearby G to M-dwarfs and the analysis of the variability of fundamental physical constants. The project passed the final design review in May 2013 and entered the manufacturing phase. ESPRESSO will be installed at the Paranal Observatory in 2016 and its operation is planned to start by the end of the same year., Comment: 12 pages, figures included, accepted for publication in Astron. Nachr

Building on the experience of the high-resolution community with the suite of VLT high-resolution spectrographs, which has been tremendously successful, we outline here the (science) case for a high-fidelity, high-resolution spectrograph with wide wavelength coverage at the E-ELT. Flagship science drivers include: the study of exo-planetary atmospheres with the prospect of the detection of signatures of life on rocky planets; the chemical composition of planetary debris on the surface of white dwarfs; the spectroscopic study of protoplanetary and proto-stellar disks; the extension of Galactic archaeology to the Local Group and beyond; spectroscopic studies of the evolution of galaxies with samples that, unlike now, are no longer restricted to strongly star forming and/or very massive galaxies; the unraveling of the complex roles of stellar and AGN feedback; the study of the chemical signatures imprinted by population III stars on the IGM during the epoch of reionization; the exciting possibility of paradigm-changing contributions to fundamental physics. The requirements of these science cases can be met by a stable instrument with a spectral resolution of R~100,000 and broad, simultaneous spectral coverage extending from 370nm to 2500nm. Most science cases do not require spatially resolved information, and can be pursued in seeing-limited mode, although some of them would benefit by the E-ELT diffraction limited resolution. Some multiplexing would also be beneficial for some of the science cases. (Abridged), Comment: 49 pages, 16 figures, White Paper for E-ELT HIRES (a few typos corrected)

On 21 March 2013 high-resolution slit spectrographs of comet C/2011 L4 (Panstarrs), at the heliocentric distance r = 0.46 Astronomical Units (AU), were obtained at the Osservatorio Astronomico Campo dei Fiori, Italy. Emission lines of sodium were the strongest in the spectrum as is common in comets, but also potassium lines were detected. These have been rarely observed in comets since the apparition of brightest comet C/1965 S1 (Ikeya-Seki). Lithium was not detected, and stringent upper limits of its abundance compared to other alkali were derived. We obtain abundance ratios Na/K = 54 +/-14 and Na/Li > 8000. As well as in Mercury exosphere (Leblanc & Douressoundiram 2011)}, we show that photoionization at the beginning of the alkali tails may increase the solar ratio Na/K = 15.5 (Asplund et al 2009) by a factor 3, close to that required to match the observed value. In the same tail position the Na/Li ratio increases by a factor 2 only, very far from the factor > 8 required to match an original meteoritic ratio. We apply the same model to similar alkali data (Preston 1967) of comet C/1965 S1 (Ikeya-Seki), obtaining consistent results. An original solar Na/K ratio fits the observed value at the beginning of the alkali tails within the slit size, whereas Li is depleted by a factor > 8., Comment: 15 pages, 4 figures. ApJL 2013