The acronym ESPRESSO stems for Echelle SPectrograph for RockyExoplanets and Stable Spectroscopic Observations; this instrument will be the next VLTh igh resolution spectrograph. The spectrograph will be installed at the CombinedCoudéL aboratory of the VLTa nd linked to the four 8.2 mU nit Telescopes (UT) through four optical Coudét rains. ESPRESSO will combine efficiencya nd extreme spectroscopic precision. ESPRESSO is foreseen to achieve ag ain of twomagnitudes with respect to its predecessor HARPS, and to improve the instrumental radial-velocity precision to reach the 10 cm s −1 level. It can be operated either with as ingle 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 allowtoexplore newfrontiers in most domains of astrophysics that require precision and sensitivity.The main scientific drivers are the search and characterization of rockyexoplanets in the habitable zone of quiet, nearby GtoM-dwarfs and the analysis of the variability of fundamental physical constants. The project passed the final design reviewinMay 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. 1I ntroductionHigh-resolution spectroscopy provides physical insights in the study of stars, galaxies, and interstellarand intergalactic medium.B esides the importance of observing fainter and fainter objects by increasing the photon collecting area by making bigger telescopes, the importance of high-precision has emerged in recent years as ac rucial element in spectroscopy. In manyi nvestigations repeatable observations overl ong temporal baseline are needed. Fori nstance, the Corresponding author: molaro@oats.inaf.it HARPS spectrograph at the ESO 3.6-m telescope is ap ioneering instrument for precise radial-velocity (RV) measurements (Mayor et al. 2003). The search for terrestrial planets in habitable zone is one of the most exciting science topics of the next decades and one of the main drivers for the newg eneration of Extremely Large Telescopes. The need for as imilar instrument on the VLTh as been emphasized in the ESO-ESA working group report on extrasolar planets. In October 2007 the ESO STC recommended the development of additional second-generation VLTi nstruments, and this proposal wasendorsed by the ESO Council in December of the same year.Among the recommended instru-

We report on the first detection of very high-energy (VHE) gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. The result has been achieved by means of the 4 m size ASTRI-Horn telescope, operated on Mt. Etna (Italy) and developed in the context of the Cherenkov Telescope Array Observatory preparatory phase. The dual-mirror SC design is aplanatic and characterized by a small plate scale, allowing us to implement large field of view cameras with small-size pixel sensors and a high compactness.The curved focal plane of the ASTRI camera is covered by silicon photo-multipliers (SiPMs), managed by an unconventional front-end electronics based on a customized peak-sensing detector mode. The system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. The observations of the Crab Nebula were carried out in December 2018, during the telescope verification phase, for a total observation time (after data selection) of 24.4 h, equally divided into on-and off-axis source exposure. The camera system was still under commissioning and its functionality was not yet completely exploited. Furthermore, due to recent eruptions of the Etna Volcano, the mirror reflection efficiency was reduced. Nevertheless, the observations led to the detection of the source with a statistical significance of 5.4 σ above an energy threshold of ∼3 TeV. This result provides an important step towards the use of dual-mirror systems in Cherenkov gamma-ray astronomy. A pathfinder mini-array based on nine large field-of-view ASTRI-like telescopes is under implementation.

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We present the results of a year-long photometric monitoring campaign of a sample of 23 nearby (d < 60 pc), bright (J < 12) dM stars carried out at the Astronomical Observatory of the Autonomous Region of the Aosta Valley, in the western Italian Alps. This programme represents a 'pilot study' for a long-term photometric transit search for planets around a large sample of nearby M dwarfs, due to start with an array of identical 40-cm class telescopes by the Spring of 2012. In this study, we set out to (i) demonstrate the sensitivity to <4 R ⊕ transiting planets with periods of a few days around our programme stars, through a two-fold approach that combines a characterization of the statistical noise properties of our photometry with the determination of transit detection probabilities via simulations; and (ii) where possible, improve our knowledge of some astrophysical properties (e.g. activity, rotation) of our targets by combining spectroscopic information and our differential photometric measurements. We achieve a typical nightly root mean square (RMS) photometric precision of ∼5 mmag, with little or no dependence on the instrumentation used or on the details of the adopted methods for differential photometry. The presence of correlated (red) noise in our data degrades the precision by a factor of ∼1.3 with respect to a pure white noise regime. Based on a detailed stellar variability analysis (i) we detected no transit-like events (an expected result, given the sample size); (ii) we determined photometric rotation periods of ∼0.47 and ∼0.22 d for LHS 3445 and GJ 1167A, respectively; (iii) these values agree with the large projected rotational velocities (∼25 and ∼33 km s −1 , respectively) inferred for both stars based on the analysis of archival spectra; (iv) the estimated inclinations of the stellar rotation axes for LHS 3445 and GJ 1167A are consistent with those derived using a simple spot model; and (v) short-term, low-amplitude flaring events were recorded for LHS 3445 and LHS 2686. Finally, based on simulations of transit signals of given period and amplitude injected in the actual (nightly reduced) photometric data for our sample, we derive a relationship between transit detection probability and phase coverage. We find that, using the Box-fitting Least Squares search algorithm, even when the phase coverage approaches 100 per cent, there is a limit to the detection probability of ≈90 per cent. Around programme stars with phase coverage > 50 per cent, we would have had >80 per cent chances of detecting planets with P < 1 d inducing fractional transit depths > 0.5 per cent, corresponding to minimum detectable radii in the range ∼1.0-2.2 R ⊕ . These findings are illustrative of our high readiness level ahead of the main survey start.