Lithium abundance derived in metal-poor main-sequence (MS) stars is about three times lower than the value of primordial Li predicted by the standard big bang nucleosynthesis when the baryon density ...is taken from the cosmic microwave background or the deuterium measurements. This disagreement is generally referred as the lithium problem. We here reconsider the stellar Li evolution from the pre-main sequence (PMS) to the end of the MS phase by introducing the effects of convective overshooting (OV) and residual mass accretion. We show that 7Li could be significantly depleted by convective OV in the PMS phase and then partially restored in the stellar atmosphere by a tail of matter accretion which follows the Li-depletion phase and that could be regulated by EUV photoevaporation. By considering the conventional nuclear burning and microscopic diffusion along the MS, we can reproduce the Spite plateau for stars with initial mass m
0 = 0.62–0.80 M⊙, and the Li declining branch for lower mass dwarfs, e.g. m
0 = 0.57–0.60 M⊙, for a wide range of metallicities (Z = 0.00001 to Z = 0.0005), starting from an initial Li abundance A(Li) = 2.72. This environmental Li evolution model also offers the possibility to interpret the decrease of Li abundance in extremely metal-poor stars, the Li disparities in spectroscopic binaries and the low Li abundance in planet hosting stars.
Classical novae with CUBES Izzo, Luca; Molaro, Paolo; Bonifacio, Piercarlo ...
Experimental astronomy,
02/2023, Letnik:
55, Številka:
1
Journal Article
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Odprti dostop
Among the main science cases that have motivated the proposal of CUBES, a new high-resolution spectrograph for the Very Large Telescope at the European Southern Observatory, there is the study and ...the characterisation of the nucleosynthesis of beryllium. Classical novae have been proposed since the ’70s as one of the main factories of lithium in the Galaxy, but this hypothesis has been demonstrated on empirical basis only recently thanks to the direct identification of lithium in V1369 Cen and through the observations of the resonance transition of
7
Be II, the
7
Li parent, at 313.0 nm in the near-UV range. CUBES is then the ideal instrument to quantify the amount of
7
Be and therefore of
7
Li produced by the different novae types hosted in the different components of the Milky Way and also in its nearby satellite galaxies. As important by-product of high resolution spectroscopic observations obtained with CUBES, there are the study of the properties of nova ejecta abundances, the shocks evolution in novae and their connection with the high-energy emission observed in these transients, from satellites as Fermi and Swift.
Observations of the redshift
= 7.085 quasar J1120+0641 are used to search for variations of the fine structure constant, a, over the redshift range 5:5 to 7:1. Observations at
= 7:1 probe the physics ...of the universe at only 0.8 billion years old. These are the most distant direct measurements of a to date and the first measurements using a near-IR spectrograph. A new AI analysis method is employed. Four measurements from the x-shooter spectrograph on the Very Large Telescope (VLT) constrain changes in a relative to the terrestrial value (α
). The weighted mean electromagnetic force in this location in the universe deviates from the terrestrial value by Δα/α = (α
- α
)/α
= (-2:18 ± 7:27) × 10
, consistent with no temporal change. Combining these measurements with existing data, we find a spatial variation is preferred over a no-variation model at the 3:9σ level.
Abstract
Chisel marks on a stone uncovered in Rupinpiccolo protohistoric hill fort from north‐eastern Italy were suggested to be a representation of the night sky (Bernardini et al. 2022
Documenta ...Praehistorica XLIX
). The patterns of the 29 marks are analyzed here to establish if they reproduce popular stellar asterisms. Nine marks are found to match the Tail of Scorpius and five the Orion's Belt, together with Rigel and Betelgeuse. Nine marks are found in the approximate position of the Pleiades showing some match with the cluster members. On the back side, 5 marks possibly reproduce Cassiopeia. One mark slightly North of Orion cannot be identified. The 28 marks show a Pearson correlation coefficient (28) with stellar positions higher than 0.99 with a probability of a wrong correlation lower than 0.001. Departures are about one degree, or about 7 mm, as the mean diameter of the marks, which suggests a manufacturing limitation in the charting. The fort dates 1800–400 BCE when Scorpius and Orion showed about the same orientation at the heliacal rising. The unidentified mark challenges the whole picture. We suggest it could have been the progenitor of a failed supernova, thus offering also the possibility of a verification.
Absorption systems observed along the line of sights to distant quasars are observed at all redshifts and the full range of the electromagnetic spectrum is needed to recover the variety of ...transitions of different elements. However, some important elements are found within the Lyman forest and their absorption line profiles need to be analyzed against the presence of possible Ly-
α
contamination. Considering the cosmological evolution of the number density of hydrogen clouds, the probability to detect uncontaminated metal lines is higher in the UV-Optical region exploited by CUBES. The list of these elements includes some important ones such as D, H
2
, O
i
, N
i
, O
vi
, Ar
i
, P
ii
, C
ii
, S
ii
and B
ii
. The determination of some of them in the Damped Ly-
α
galaxies and their astronomical interest are briefly discussed.
ESPRESSO is a high-resolution-ultra-stable spectrograph for the Very Large Telescope (VLT), whose commissioning will start in 2017. One of its key science goals is to test the stability of nature’s ...fundamental couplings with unprecedented accuracy and control of possible systematics. A total of 27 nights of the ESPRESSO Consortium’s guaranteed time observations (GTO) will be spent on testing the stability of the fine-structure constant and other fundamental couplings. A set of 14 priority optimal targets have been selected for the GTO period. In this work, we discuss the criteria underlying this selection, describe the selected targets, and present some forecasts of the impact of these measurements on fundamental physics and cosmology, focusing on dark energy constraints and using future supernova type Ia surveys as a comparison point. This report is a summary of the results reported in Phys. Rev. D 2016, 94, 123512, to which we refer the reader for further details.
ABSTRACT
New observations of the quasar HE0515−4414 have been made, aided by the Laser Frequency Comb (LFC), using the HARPS spectrograph on the ESO 3.6m telescope. We present three important ...advances for α measurements in quasar absorption spectra from these observations. First, the data have been wavelength calibrated using LFC and ThAr methods. The LFC wavelength calibration residuals are six times smaller than when using the standard ThAr calibration. We give a direct comparison between α measurements made using the two methods. Secondly, spectral modelling was performed using Artificial Intelligence (fully automated, all human bias eliminated), including a temperature parameter for each absorption component. Thirdly, in contrast to previous work, additional model parameters were assigned to measure α for each individual absorption component. The increase in statistical uncertainty from the larger number of model parameters is small and the method allows a substantial advantage; outliers that would otherwise contribute a significant systematic, possibly corrupting the entire measurement, are identified and removed, permitting a more robust overall result. The $z$abs = 1.15 absorption system along the HE0515−4414 sightline yields 40 new α measurements. We constrain spatial fluctuations in α to be Δα/α ≤ 9 × 10−5 on scales $\approx \!\! {20}\, {\rm km\, s}^{-1}$, corresponding to $\approx 25\,$kpc if the $z$abs = 1.15 system arises in a 1Mpc cluster. Collectively, the 40 measurements yield Δα/α = −0.27 ± 2.41 × 10−6, consistent with no variation.
Before becoming the great scientist that everyone knows and the founding father of modern science, the young Galileo Galilei was nurtured within a typically Renaissance context, acquiring a marked ...artistic sensibility which transpires in his literary style and even in his scientific work. Galileo was indeed a musician, an intellectual and also a painter, as consensually recorded in his first biographies and as illustrated by watercolours of his first observations of the Moon and his drawings of the sunspots. However there is also a somewhat astonishing reference to the existence of an actual self-portrait, as recorded by Thomas Salusbury (1664) in what continues to be the first biography of Galileo to have been published. Recently a possible new youthful portrait of Galileo Galilei has been proposed. The remarkable similarity of this new portrait with those of Domenico Tintoretto (circa 1604), Santi di Tito (1601, via Calendi) and Furini (1612) has recently been confirmed using sophisticated face recognition techniques (Srinivasan et al 2015, Rudolph et al 2015). Were the identity to be definitively ascertained, other elements which emerged from the infrared analysis of the painting--such as Sommario. Prima di divenire il grande scienziato che tutti conosciamo e padre fondatore della scienza moderna il giovane Galileo Galilei si formo in un ambiente squisitamente rinascimentale acquisendo una spiccata sensibilita artistica che traspare nel suo stile letterario e perfino nella sua attivita scientifica. Fu musico, letterato e anche pittore come concordemente riportato nelle sue prime biografie e come testimoniano gli acquerelli delle sue prime osservazioni lunari o i disegni delle macchie solari. Ma un riferimento per certi versi stupefacente riguarda l'esistenza di un autoritratto come riportato da Thomas Salusbury (1664) in quella che rimane la prima biografia pubblicata su Galileo. Recentemente e stato posto all'attenzione degli studiosi un possibile nuovo ritratto giovanile di Galileo Galilei. La notevole somiglianza con i ritratti di Domenico Tintoretto (1604, circa), di Santi di Tito (1601, via Calendi) e del Furini (1612) e stata recentemente confermata con sofisticate tecniche di riconoscimento facciale (Srinivasan et al 2015, Rudolph et al 2015). Se l'identita fosse definitivamente accertata altri elementi quali la giovane eta o la tela ricucita emersa dall'analisi in infrarosso del dipinto sembrerebbero suggerire un collegamento proprio con l'opera menzionata da Thomas Salusbury. Parole chiave. Galileo Galilei, ritratti, biografie, Thomas Salusbury, Cigoli, Tintoretto, identificazione Facciale the young age or the restitched canvas--would appear to suggest a connection with the very work mentioned by Thomas Salusbury. Keywords. Galileo Galilei, portraits, biographies, Thomas Salusbury, Cigoli, Tintoretto, face recognition.
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