UVES radial velocity accuracy from asteroid observations. Implications for the fine structure constant variability

High resolution observations of the asteroids Iris and Juno have been performed by means of the UVES spectrograph at the ESO VLT to obtain the effective accurac y of the spectrograph's radial velocity. The knowledge of this quantity has impo rtant bearings on studies searching for a variability of the fine structure cons tant carried on with this instrument. Asteroids provide a precise radial velocit y reference at the level of 1 m/s which allows instrumental calibration and the recognition of small instrumental drifts and calibration systematics. In particu lar, radial velocity drifts due to non uniform slit illumination and slit optica l misalignment in the two UVES spectrograph arms can be investigated. The positi on of the solar spectrum reflected by the asteroids are compared with the solar wavelength positions or with that of asteroid observations at other epochs or wi th the twilight to asses UVES instrumental accuracy . Radial velocities offsets in the range 10--50 m/s are generally observed likely due to a non uniform slit illumination. However, no radial velocity patterns with wavelength are detected and the two UVES arms provide consistent radial velocities. These results suggest that the detected alpha variability by Levshakov et al. (2007) deduced from a drift of -180 (+/- 85) m/s at z =1.84, between two sets of FeII lines falling in the two UVES arms may be real or induced by other kinds of systematics than those investigated here. The proposed technique allows real time quality check of the spectrograph and should be followed for very accurate measurements.Comment: Accepted A&

SVILUPPO E RISULTATI DI UNA METODICA COMPUTER ASSISTITA PER L’ANALISI APPROFONDITA DI EVENTI INFORTUNISTICI LAVORO CORRELATI

In Italia si deve tutt’ora registrare un elevato numero di eventi mortali lavoro correlati, per la stragrande maggioranza in contesti non ascrivibili a scenari di incidente rilevante, e raramente associabili a guasto di impianti ed attrezzature correttamente scelti, usati e mantenuti. Un approccio efficace di prevenzione non può che fare riferimento all’analisi dei dati storici, ad integrazione della quale occorre peraltro disporre di una metodica di analisi della catena di eventi casuali dell’incidente formalizzata e priva di deviazioni valutative soggettive. Il modello originale di cui si riferisce si fonda su casi caratterizzati da informazioni approfondite acquisite in ambito di accertamenti tecnici a fini di giustizia. Esso si propone come valido riferimento nelle valutazioni sino alle cause prime dell’evento, lungo tutta la catena incidentale, e consente la revisione critica della valutazione e gestione proattiva dei rischi

A Frequency Comb calibrated Solar Atlas

The solar spectrum is a primary reference for the study of physical processes in stars and their variation during activity cycles. In Nov 2010 an experiment with a prototype of a Laser Frequency Comb (LFC) calibration system was performed with the HARPS spectrograph of the 3.6m ESO telescope at La Silla during which high signal-to-noise spectra of the Moon were obtained. We exploit those Echelle spectra to study the optical integrated solar spectrum . The DAOSPEC program is used to measure solar line positions through gaussian fitting in an automatic way. We first apply the LFC solar spectrum to characterize the CCDs of the HARPS spectrograph. The comparison of the LFC and Th-Ar calibrated spectra reveals S-type distortions on each order along the whole spectral range with an amplitude of +/-40 m/s. This confirms the pattern found by Wilken et al. (2010) on a single order and extends the detection of the distortions to the whole analyzed region revealing that the precise shape varies with wavelength. A new data reduction is implemented to deal with CCD pixel inequalities to obtain a wavelength corrected solar spectrum. By using this spectrum we provide a new LFC calibrated solar atlas with 400 line positions in the range of 476-530, and 175 lines in the 534-585 nm range. The new LFC atlas improves the accuracy of individual lines by a significant factor reaching a mean value of about 10 m/s. The LFC--based solar line wavelengths are essentially free of major instrumental effects and provide a reference for absolute solar line positions. We suggest that future LFC observations could be used to trace small radial velocity changes of the whole solar photospheric spectrum in connection with the solar cycle and for direct comparison with the predicted line positions of 3D radiative hydrodynamical models of the solar photosphere.Comment: Accept on the 15th of October 2013. 9 pages, 10 figures. ON-lINE data A&A 201

Climate and atmospheric models of rocky planets: habitability and observational properties

The quest for atmospheric spectral signatures that may witness biological activity in exoplanets is focused on rocky planets. The best targets for future, challenging spectroscopic observations will be selected among potentially habitable planets. Surface habitability can be quantified and explored with climate and atmospheric models according to temperature-based criteria. The conceptual, modellistic, technological and interpretative complexity of the problem requires to develop flexible climate and atmospheric models suited for a comprehensive exploration of observationally unconstrained parameters, and to simulate and interpret definitely non-terrestrial conditions. We present a summary and preliminary results on the work we are performing on multi-parametric explorations of the habitability and observational properties of rocky planets.Comment: to appear on MemSAIt, vol 94. Proceedings of the Hack100 Conference: Past, Present and Future of Astrophysical Spectroscopy, 6-10 June 2022, Trieste, Ital

A search for Interstellar absorptions towards Sgr dSph

We searched for Na I D1,D2 interstellar absorption lines towards 12 giant stars of the Sgr dwarf spheroidal and 3 stars of the associated globular cluster Terzan 7, observed at high resolution with the UVES spectrograph at the 8.2 m Kueyen VLT telescope. These stars are not an ideal background source for the analysis of interstellar (IS) absorption lines since they have been observed in the framework of a stellar abundances study. However they are sufficiently luminous to allow a decent S/N ratio at a resolution of about 43000, i.e. ~7 km/s, which allows an exploratory study. We detected two distinct groups of IS absorptions, a ``local'' group, with radial velocities ranging from -43 km/s to 50 km/s, and a high velocity group with radial velocities ranging from 150 km/s to 165 km/s. Likely the high velocity components are due to gas falling on the Sgr dSph since have been observed only in 2 stars which are separated by only 1.5' in the sky. We argue that the observations suggest a stripping of gas due to the passage of Sgr through the Galactic disc.Comment: accepted by Astronomy & Astrophysic

Seasonal thaws under mid-to-low pressure atmospheres on Early Mars

Despite decades of scientific research on the subject, the climate of the first 1.5 Gyr of Mars history has not been fully understood yet. Especially challenging is the need to reconcile the presence of liquid water for extended periods of time on the martian surface with the comparatively low insolation received by the planet, a problem which is known as the Faint Young Sun (FYS) Paradox. In this paper we use ESTM, a latitudinal energy balance model with enhanced prescriptions for meridional heat diffusion, and the radiative transfer code EOS to investigate how seasonal variations of temperature can give rise to local conditions which are conductive to liquid water runoffs. We include the effects of the martian dichotomy, a northern ocean with either 150 or 550 m of Global Equivalent Layer (GEL) and simplified CO$_2$ or H$_2$O clouds. We find that 1.3-to-2.0 bar CO$_2$-dominated atmospheres can produce seasonal thaws due to inefficient heat redistribution, provided that the eccentricity and the obliquity of the planet are sufficiently different from zero. We also studied the impact of different values for the argument of perihelion. When local favorable conditions exist, they nearly always persist for $>15\%$ of the martian year. These results are obtained without the need for additional greenhouse gases (e.g. H$_2$, CH$_4$) or transient heat-injecting phenomena (e.g. asteroid impacts, volcanic eruptions). Moderate amounts (0.1 to 1\%) of CH$_4$ significantly widens the parameter space region in which seasonal thaws are possible.Comment: Second and final version, 27 pages, 10 figures, accepted for publication in Ap

A wide angle view of the Sagittarius dwarf Spheroidal Galaxy. I: VIMOS photometry and radial velocities across Sgr dSph major and minor axis

The Sagittarius dwarf Spheroidal Galaxy (Sgr dSph) provides us with a unique possibility of studying a dwarf galaxy merging event while still in progress. Due to its low distance (25 kpc), the main body of Sgr dSph covers a vast area in the sky (roughly 15 x 7 degrees). Available photometric and spectroscopic studies have concentrated either on the central part of the galaxy or on the stellar stream, but the overwhelming majority of the galaxy body has never been probed. The aim of the present study is twofold. On the one hand, to produce color magnitude diagrams across the extension of Sgr dSph to study its stellar populations, searching for age and/or composition gradients (or lack thereof). On the other hand, to derive spectroscopic low-resolution radial velocities for a subsample of stars to determine membership to Sgr dSph for the purpose of high resolution spectroscopic follow-up. We used VIMOS-VLT to produce V and I photometry and spectroscopy on 7 fields across the Sgr dSph minor and major axis, plus 3 more centered on the associated globular clusters Terzan 7, Terzan 8 and Arp 2. A last field has been centered on M 54, lying in the center of Sgr dSph. We present photometry for 320,000 stars across the main body of Sgr dSph, one of the richest, and safely the most wide-angle sampling ever produced for this fundamental object. We also provide robust memberships for more than one hundred stars, whose high resolution spectroscopic analysis will be the object of forthcoming papers. Sgr dSph appears remarkably uniform among the observed fields. We confirm the presence of a main Sgr dSph population characterized roughly by the same metallicity of 47 Tuc, but we also found the presence of multiple populations on the peripheral fields of the galaxy, with a metallicity spanning from [Fe/H]=-2.3 to a nearly solar value.Comment: 10 pages, 12 figures, accepted for publication in A&

Neuronal networks provide rapid neuroprotection against spreading toxicity

Acute secondary neuronal cell death, as seen in neurodegenerative disease, cerebral ischemia (stroke) and traumatic brain injury (TBI), drives spreading neurotoxicity into surrounding, undamaged, brain areas. This spreading toxicity occurs via two mechanisms, synaptic toxicity through hyperactivity, and excitotoxicity following the accumulation of extracellular glutamate. To date, there are no fast-acting therapeutic tools capable of terminating secondary spreading toxicity within a time frame relevant to the emergency treatment of stroke or TBI patients. Here, using hippocampal neurons (DIV 15-20) cultured in microfluidic devices in order to deliver a localized excitotoxic insult, we replicate secondary spreading toxicity and demonstrate that this process is driven by GluN2B receptors. In addition to the modeling of spreading toxicity, this approach has uncovered a previously unknown, fast acting, GluN2A-dependent neuroprotective signaling mechanism. This mechanism utilizes the innate capacity of surrounding neuronal networks to provide protection against both forms of spreading neuronal toxicity, synaptic hyperactivity and direct glutamate excitotoxicity. Importantly, network neuroprotection against spreading toxicity can be effectively stimulated after an excitotoxic insult has been delivered, and may identify a new therapeutic window to limit brain damage

Criteri di approccio alla valutazione e gestione del rischio

Convegno in Apicoltura – corso di formazione per la prevenzione dei rischi in apicoltura , Coldiretti, Asti, 28 marzo 201

Criteri di approccio alla valutazione e gestione del rischio

Convegno in Apicoltura - corso di formazione per la prevenzione dei rischi in apicoltura , Coldiretti, Asti, 28 marzo 201