Scilla Degl'Innocenti

• PhD
• Professor (Associate) at University of Pisa

Aims. We investigated the possibility of using two recently characterised triply eclipsing triple systems to constrain stellar model parameters. We specifically focused on evaluating the influence of the underlying astrophysical assumptions employed in the characterisation of the system to fix absolute values of the radii, effective temperatures, a...

We investigated the possibility of using two recently characterised triply eclipsing triple systems to constrain stellar model parameters. We specifically focused on evaluating the influence of the underlying astrophysical assumptions employed in the characterisation of the system to fix absolute values of the radii, effective temperatures, and met...

Context. A recent investigation highlighted peculiar trends between the radii derived from surface brightness-colour relations (SBCRs) combined with Gaia DR3 parallaxes with respect to asteroseismic scaling relation radii from K2 data. Aims.Kepler data differ from K2 data in many aspects. We investigated on the robustness of the results based on Ke...

A recent investigation highlighted peculiar trends between the radii derived from surface brightness-colour relations (SBCRs) combined with Gaia DR3 parallaxes with respect to asteroseismic scaling relation radii from K2 data. [...] We investigated on the robustness of the results based on Kepler data. We cross-matched asteroseismic and astrometric...

Aims. We compared stellar radii derived from asteroseismic scaling relations with those estimated using two independent surface brightness-colour relations (SBCRs) combined with Gaia DR3 parallaxes. Methods. We cross-matched asteroseismic and astrometric data for over 6400 red giant branch (RGB) and red clump (RC) stars from the APO-K2 catalogue wi...

We compared stellar radii derived from asteroseismic scaling relations with those estimated using two independent surface brightness-colour relations (SBCRs) and Gaia DR3 parallaxes. We cross-matched asteroseismic and astrometric data for over 6,400 RGB and RC stars from the APO-K2 catalogue with the TESS Input Catalogue v8.2 to obtain precise V ba...

By adopting the recently empirically derived dependence of $\alpha$-elements on $[\alpha/{\rm Fe}]$ instead of the conventionally applied uniform one, we tested the agreement between stellar model predictions and observations for red giant branch (RGB) stars in the APO-K2 catalogue. We particularly focused on the biases in effective temperature sca...

Aims. By adopting the recently empirically derived dependence of α -elements on [ α /Fe] instead of the conventionally applied uniform one, we tested the agreement between stellar model predictions and observations for red giant branch (RGB) stars in the APO-K2 catalogue. We particularly focused on the biases in effective temperature scales and on...

Aims. We conducted an investigation on the chemical abundances of 4316 stars in the red giant branch (RGB) phase from the recently released APO-K2 catalogue. Our aim was to characterize the abundance trends of the single elements with [ α /Fe], mainly focusing on C, N, and O, which are the most relevant for the estimation of stellar ages. Methods....

We conducted an investigation on the chemical abundances of 4,316 stars in the red giant branch (RGB) phase from the recently released APO-K2 catalogue. Our aim was to characterize the abundance trends of the single elements with [$\alpha$/Fe], mainly focusing on C, N, and O, which are the most relevant for the estimation of stellar ages. The chemi...

PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars...

Aims. We aim to investigate the theoretical possibility of accurately determining the helium-to-metal enrichment ratio Δ Y /Δ Z from precise observations of double-lined eclipsing binary systems. Methods. Using Monte Carlo simulations, we drew synthetic binary systems with masses between 0.85 and 1.00 M ⊙ from a grid of stellar models. Both stars w...

We investigated the theoretical possibility of accurately determining the helium-to-metal enrichment ratio $\Delta Y/\Delta Z$ from precise observations of double lined eclipsing binary systems. Using Monte Carlo simulations, we drew synthetic binary systems with masses between 0.85 and 1.00 $M_{\odot}$ from a grid of stellar models with $\Delta Y/...

Aims. We investigated the theoretical biases affecting the asteroseismic grid-based estimates of stellar mass, radius, and age in the presence of a mismatch between the heavy element mixture of observed stars and stellar models. Methods. We performed a controlled simulation adopting a stellar effective temperature, [Fe/H], an average large frequenc...

Photometric time series gathered by space telescopes such as CoRoT and Kepler allow to detect solar-like oscillations in red giant stars and to measure their global seismic constraints, which can be used to infer global stellar properties (e.g. masses, radii, and evolutionary states). Combining such precise constraints with photospheric abundances...

The next years will see the completion of several new facilities at Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali del Sud (LNS) opening up new possibilities in the fields of nuclear structure, nuclear dynamics, nuclear astrophysics and applications. These include a new line for high-intensity cyclotron beams, a new facility for in-fl...

Aims. We aim to estimate the impact on the stellar evolution of the uncertainties in the 3 α and the ¹² C( α , γ ) ¹⁶ O reaction rates, taking into account the recent improvements in their precision. Methods. We calculated models of low- and intermediate-mass stars for different values of 3 α and ¹² C( α , γ ) ¹⁶ O reaction rates. The 3 α reaction...

Aims. Relying on recently available and very precise observational data for the Ai Phe binary system, we explore the robustness of the calibration of stellar models achievable with this system. Methods. We adopt the SCEPtER pipeline with a fitting grid of stellar models computed for different initial chemical compositions and convective core oversh...

Aims. Relying on recent very precise observations for the CPD-54 810 binary system, we investigate the robustness of the estimated age and convective core overshooting for a system with both stars on the main sequence (MS). Our main aim is to assess the variability in the results, accounting for different statistical and systematic sources of uncer...

Relying on precise observations for the CPD-54 810 binary system, we investigate the robustness of the estimated age and convective core overshooting for a system with both stars on the main sequence (MS). [...] We adopt the SCEPtER pipeline, based on grids of stellar models computed for a different initial chemical composition and convective core...

Context. Stellar age determinations for field stars are crucial for studying the evolutionary history of the Galaxy. The vast majority of the research in this area has so far been focused on stars with typical disk characteristics. Aims. Nowadays, the availability of high-quality asteroseismic data for stars with typical halo characteristics makes...

[...] The aim of this paper is to study the precision and theoretical biases in the age determinations of halo stars adopting both asteroseismic and classic observational constraints. [...] We adopt the well-tested SCEPtER pipeline, covering evolutionary phases up to the red giant branch (RGB). The fitting grids contain stars with mass in the range...

Stellar evolution and element nucleosynthesis involve a wide range of interacting physical processes whose knowledge is fundamental to understand the astrophysical phenomena. Several nuclear processes hold the keys to many of the most intriguing problems. However, their studies can be challenging and a number of issues can be better understood by m...

Context. It is now well-known that pre-main-sequence models with inflated radii should be taken into account to simultaneously reproduce the colour-magnitude diagram and the lithium depletion pattern observed in young open star clusters. Aims. We tested a new set of pre-main-sequence models that include radius inflation due to the presence of stars...

Pre-main sequence models with inflated radii are needed to simultaneously reproduce the colour-magnitude diagram and the lithium depletion pattern in young open clusters. We test a new set of PMS models including radius inflation due to starspots or to magnetic inhibition of convection, using five clusters observed by the Gaia-ESO Survey, spanning...

Spectroscopy from the final internal data release of the Gaia-ESO Survey (GES) has been combined with Gaia EDR3 to assign membership probabilities to targets observed towards 63 Galactic open clusters and 7 globular clusters. The membership probabilities are based chiefly on maximum likelihood modelling of the 3D kinematics of the targets, separati...

Spectroscopy from the final internal data release of the Gaia-ESO Survey (GES) has been combined with Gaia EDR3 to assign membership probabilities to targets observed towards 63 Galactic open clusters and 7 globular clusters. The membership probabilities are based chiefly on maximum likelihood modelling of the 3D kinematics of the targets, separati...

Theoretical prediction of surface stellar abundances of light elements -- lithium, beryllium, and boron -- represents one of the most interesting open problems in astrophysics. As well known, several measurements of 7-Li abundances in stellar atmospheres point out a disagreement between predictions and observations in different stellar evolutionary...

We aim to constrain the mixing processes in low-mass stars by investigating the behaviour of the Li surface abundance after the main sequence. We take advantage of the data from the sixth internal data release of Gaia-ESO, idr6, and from the Gaia Early Data Release 3, edr3. We select a sample of main sequence, sub-giant, and giant stars in which Li...

Theoretical prediction of surface stellar abundances of light elements–lithium, beryllium, and boron–represents one of the most interesting open problems in astrophysics. As well known, several measurements of 7Li abundances in stellar atmospheres point out a disagreement between predictions and observations in different stellar evolutionary phases...

Light elements offer a unique opportunity for studying several astrophysical scenarios from Big Bang Nucleosynthesis to stellar physics. Understanding the stellar abundances of light elements is key to obtaining information on internal stellar structures and mixing phenomena in different evolutionary phases, such as the pre-main-sequence, main-sequ...

We tested the capability of a Bayesian procedure to calibrate both the helium abundance and the mixing length parameter ($\alpha_{ML}$), using precise photometric data for main-sequence (MS) stars in a cluster with negligible reddening and well-determined distance. The method has been applied first to a mock data set generated to mimic Hyades MS st...

We tested the capability of a Bayesian procedure to calibrate both the helium abundance and the mixing length parameter (αML), using precise photometric data for main sequence (MS) stars in a cluster with negligible reddening and well determined distance. The method has been applied first to a mock dataset generated to mimic Hyades MS stars and the...

We collected over 6000 high-resolution spectra of four dozen field RR Lyrae (RRL) variables pulsating either in the fundamental (39 RRab) or in the first overtone (9 RRc) mode. We measured radial velocities (RVs) of four strong metallic and four Balmer lines along the entire pulsational cycle and derived RV amplitudes with accuracies better than 1–...

We collected over 6000 high-resolution spectra of four dozen field RR Lyrae (RRL) variables pulsating either in the fundamental (39 RRab) or in the first overtone (9 RRc) mode. We measured radial velocities (RVs) of four strong metallic and four Balmer lines along the entire pulsational cycle and derived RV amplitudes with accuracies better than 1$...

Context. The cosmological lithium problem, that is, the discrepancy between the lithium abundance predicted by the Big Bang nucleosynthesis and the one observed for the stars of the “Spite plateau”, is one of the long standing problems of modern astrophysics. Recent hints for a possible solution involve lithium burning induced by protostellar mass...

The cosmological lithium problem, that is, the discrepancy between the lithium abundance predicted by the Big Bang nucleosynthesis and the one observed for the stars of the 'Spite plateau', is one of the long standing problems of modern astrophysics. Recent hints for a possible solution involve lithium burning induced by protostellar mass accretion...

The cosmological lithium problem, i.e. the discrepancy between the lithium abundance predicted by the Big Bang Nucleosynthesis and the one observed for the stars of the "Spite plateau", is one of the long standing problems of modern astrophysics. A possible astrophysical solution involves lithium burning due to protostellar mass accretion on Spite...

Aims. We performed a theoretical analysis aimed at quantifying the relevance of the small frequency separation δν in determining stellar ages, masses, and radii. We aimed to establish a minimum uncertainty on these quantities for low-mass stars across different evolutionary stages of the main sequence and to evaluate the biases that come from some...

We performed a theoretical analysis on the relevance of the small frequency separation $\delta \nu$ in determining stellar ages, masses, and radii. We adopted the SCEPtER pipeline for low-mass stars, [0.7, 1.05] Msun. Synthetic stars were generated and reconstructed assuming different relative precision in $\delta \nu$ (5% and 2%). The quantificati...

This contribution is meant as a very brief introduction to the principal concepts of stellar physics. First the main physical processes active in stellar structures will be shortly described, then the most important features during the stellar life-cycle up to the central H exhaustion will be summarized with partic-ular attention to the description...

In the era of large high-resolution spectroscopic surveys, high-quality spectra can contribute to our understanding of the Galactic chemical evolution, providing chemical abundances belonging to the different nucleosynthesis channels, and also providing constraints to stellar age. Some abundance ratios have been proven to be excellent indicators of...

Context . Recently published high-quality OmegaCAM photometry of the 3 × 3 deg around the Orion Nebula Cluster (ONC) in r , and i filters revealed three well-separated pre-main sequences in the color-magnitude diagram (CMD). The objects belonging to the individual sequences are concentrated toward the center of the ONC. The authors concluded that t...

The high-quality OmegaCAM photometry of the 3x3 deg around the Orion Nebula Cluster (ONC) in r, and i filters by Beccari et al.(2017) revealed three well-separated pre-main sequences in the color-magnitude diagram (CMD). The objects belonging to the individual sequences are concentrated towards the center of the ONC. The authors concluded that ther...

We performed a theoretical investigation on the mixing-length parameter recovery from an eclipsing double-lined binary system. We focused on a syntetic system composed by a primary of mass M = 0.95 Msun and a secondary of M = 0.85 Msun. Monte Carlo simulations were conducted at three metallicities, and three evolutionary stages of the primary. For...

We performed a theoretical investigation on the mixing-length parameter recovery from an eclipsing double-lined binary system. We focused on a syntetic system composed by a primary of mass M = 0.95 Msun and a secondary of M = 0.85 Msun. Monte Carlo simulations were conducted at three metallicities, and three evolutionary stages of the primary. For...

Aims . We critically analysed the theoretical foundation and statistical reliability of the mixing-length calibration by means of standard ( T eff , [Fe/H]) and global asteroseismic observables (Δ ν , ν max ) of field stars. We also discussed the soundness of inferring a possible metallicity dependence of the mixing-length parameter from field star...

We analysed the theoretical foundation of the mixing-length calibration by means of classical and global asteroseismic observables of field stars. We discussed the soundness of inferring a metallicity dependence of the mixing-length parameter. We followed a theoretical approach based on mock datasets of artificial stars sampled from a grid of stell...

The main aim of this experiment is to provide a complete census of old (t > 10 Gyr, RR Lyrae, type II Cepheids, red horizontal branch), intermediate age (red clump, Miras) and young (classical Cepheids) stellar tracers across the Galactic Bulge. To fully exploit the unique photometric quality of LSST images, we plan to perform a Shallow minisurvey...

Aims. We aim to perform a theoretical investigation on the direct impact of measurement errors in the observational constraints on the recovered age for stars in main sequence (MS) and red giant branch (RGB) phases. We assumed that a mix of classical (effective temperature Teff and metallicity [Fe/H]) and asteroseismic (Δ ν and νmax ) constraints w...

We theoretically quantify the impact of observational errors on the recovered age for stars in MS and RGB phases. We adopted Teff, [Fe/H], Delta_nu and nu_max as observational constraints. Artificial stars were sampled from a reference isochrone and subjected to random perturbation to simulate observational errors. Their ages were then recovered by...

Context. Open clusters (OCs) provide a classical target to calibrate the age scale and other stellar parameters. Despite their wide use, some issues remain to be explored in detail. Aims. We performed a theoretical investigation focused on the age estimate of red giant branch (RGB) stars in OCs based on mixed classical surface ( Teff and [Fe/H]) an...

We performed a theoretical investigation focused on the age estimate of RGB stars in OCs based on mixed classical surface and asteroseismic parameters. We evaluated the performances of three widely adopted methods (pure geometrical fit, maximum likelihood approach, and a single stars fit) in recovering stellar parameters. Artificial OCs were genera...

Aims. The capability of grid-based techniques to estimate the age together with the convective core overshooting efficiency of stars in detached eclipsing binary systems for main sequence stars has previously been investigated. We have extended this investigation to later evolutionary stages and have evaluated the bias and variability on the recove...

We evaluated the bias and variability on the fitted age and convective core overshooting parameter for evolved binary stars accounting for observational and internal uncertainties. We considered a binary system composed of a 2.50 $M_{\sun}$ primary star coupled with a 2.38 $M_{\sun}$ secondary in three evolutionary stages (primary at the end of the...

We performed an analysis of the main theoretical uncertainties that affect the radius of low- and very-low mass-stars predicted by current stellar models. We focused on stars in the mass range 0.1-1Msun, on both the zero-age main-sequence (ZAMS) and on 1, 2 and 5 Gyr isochrones. First, we quantified the impact on the radius of the uncertainty of se...

We performed an analysis of the main theoretical uncertainties that affect the radius of low- and very-low mass-stars predicted by current stellar models. We focused on stars in the mass range 0.1-1Msun, on both the zero-age main-sequence (ZAMS) and on 1, 2 and 5 Gyr isochrones. First, we quantified the impact on the radius of the uncertainty of se...

Aims. We aim to perform a theoretical evaluation of the impact of the mass loss indetermination on asteroseismic grid based estimates of masses, radii, and ages of stars in the red giant branch (RGB) phase. Methods. We adopted the SCEPtER pipeline on a grid spanning the mass range [0.8; 1.8] M ⊙ . As observational constraints, we adopted the star e...

We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. The final, long-term goal is the exploitation of open clusters as age calibrators. We perform a homogeneous analysis of eight open clusters using the Gaia-DR1...

We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. The final, long-term goal is the exploitation of open clusters as age calibrators. We perform a homogeneous analysis of eight open clusters using the Gaia-DR1...

We aim to perform a theoretical evaluation of the impact of the mass loss indetermination on asteroseismic grid based estimates of masses, radii, and ages of stars in the red giant branch phase (RGB). We adopted the SCEPtER pipeline on a grid spanning the mass range [0.8; 1.8] Msun. As observational constraints, we adopted the star effective temper...

Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but...

Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but...

Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but...

The young (~2 Myr) cluster Chamaeleon I is one of the closest laboratories to study the early stages of star cluster dynamics in a low-density environment. We studied its structural and kinematical properties combining parameters from the high-resolution spectroscopic survey Gaia-ESO with data from the literature. Our main result is the evidence of...

The young (~2 Myr) cluster Chamaeleon I is one of the closest laboratories to study the early stages of star cluster dynamics in a low-density environment. We studied its structural and kinematical properties combining parameters from the high-resolution spectroscopic survey Gaia-ESO with data from the literature. Our main result is the evidence of...

We attempt to constrain the initial helium abundance, the age and the efficiency of the convective core overshooting of the binary system TZ Fornacis. Our main aim is in pointing out the biases in the results due to not accounting for some sources of uncertainty. We adopt the SCEPtER pipeline, relying on stellar models computed with two stellar evo...

We attempt to constrain the initial helium abundance, the age and the efficiency of the convective core overshooting of the binary system TZ Fornacis. Our main aim is in pointing out the biases in the results due to not accounting for some sources of uncertainty. We adopt the SCEPtER pipeline, relying on stellar models computed with two stellar evo...

New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular $\omega$ Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84x48 arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation...

New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular $\omega$ Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84x48 arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation...

The determination of the age of single stars by means of grid-based techniques is a well established method. We discuss the impact on these estimates of the uncertainties in several ingredients routinely adopted in stellar computations. The systematic bias on age determination caused by varying the assumed initial helium abundance, the mixing-lengt...

We performed a detailed analysis of the main theoretical uncertainties affecting the age at the lithium depletion boundary (LDB). We computed almost 12 000 pre-main sequence models with mass in the range [0.06, 0.4] M⊙ by varying input physics (nuclear reaction cross sections, outer boundary conditions, equation of state, and radiative opacity), in...

We analysed the effects of planet ingestion on the characteristics of a pre-MS star similar to the Gamma Velorum cluster member 2MASS J08095427–4721419 ($\#52$). We discussed the effects of changing the age t0 at which the accretion episode occurs, the mass of the ingested planet and its chemical composition. We showed that the mass of the ingested...

We analysed the effects of planet ingestion on the characteristics of a pre-MS star similar to the Gamma Velorum cluster member 2MASS J08095427--4721419 (#52). We discussed the effects of changing the age $t_0$ at which the accretion episode occurs, the mass of the ingested planet and its chemical composition. We showed that the mass of the ingeste...

The Trojan Horse Method (THM) has been largely adopted for investigating astrophysically relevant charged-particle induced reactions at Gamow energies. Indeed, THM allows one to by pass extrapolation procedures, thus overcoming this source of uncertainty. Here, the recent THM results and their impact in astrophysics are going to be discussed.

With the aim to test the present capability of the stellar surface lithium abundance in providing an estimation for the age of PMS stars, we analyze the case of the detached, double-lined, eclipsing binary system PAR 1802. For this system, the lithium age has been compared with the theoretical one, as estimated by applying a Bayesian analysis metho...

This contribution is meant as a first brief introduction to stellar physics. First I shortly describe the main physical processes active in stellar structures then I summarize the most important features during the stellar life-cycle.

We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] Msun, and on stars in the main-sequence phase. The ages were obtained by means of the maximum-likelihood S...

We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] Msun, and on stars in the main-sequence phase. The ages were obtained by means of the maximum-likelihood S...

In a robust statistical way, we quantify the uncertainty that affects the calibration of the overshooting efficiency parameter $\beta$ that is owing to the uncertainty on the observational data in double-lined eclipsing binary systems. We also quantify the bias that is caused by the lack of constraints on the initial helium content and on the effic...

STREGA (STRucture and Evolution of the Galaxy) is an ongoing VLT Survey Telescope Guaranteed Time survey, aimed at investigating the mechanisms of formation and evolution of the Galactic Halo on an area of about 150 square degrees. The core programme searches for the signatures of interaction between selected stellar systems and the Galactic Halo a...

In a robust statistical way, we quantify the uncertainty that affects the calibration of the overshooting efficiency parameter $\beta$ that is owing to the uncertainty on the observational data in double-lined eclipsing binary systems. We also quantify the bias that is caused by the lack of constraints on the initial helium content and on the effic...

Burning reaction S(E)-factor determinations are among the key ingredients for stellar models when one has to deal with energy generation evaluation and the genesis of the elements at stellar conditions. To by pass the still present uncertainties in extrapolating low-energies values, S(E)-factor measurements for charged-particle induced reactions in...

We investigated the possibility of producing helium-enhanced stars in globular clusters by accreting polluted matter during the pre-main-sequence phase. We followed the evolution of two different classes of pre-main-sequence accreting models, one which neglects and the other that takes into account the protostellar evolution. We analysed the depend...

We investigated the possibility of producing helium enhanced stars in globular clusters by accreting polluted matter during the pre-main sequence phase. We followed the evolution of two different classes of pre-main sequence accreting models, one which neglects and the other that takes into account the protostellar evolution. We analysed the depend...

The complete understanding of the stellar abundances of lithium, beryllium, and boron represents one of the most interesting open problems in astrophysics. These elements are largely used to probe stellar structure and mixing phenomena in different astrophysical scenarios, such as pre-main-sequence or main-sequence stars. Their different fragility...

We investigate the performance of grid-based techniques in estimating the age of stars in detached eclipsing binary systems. We evaluate the precision of the estimates due to the uncertainty in the observational constraints, and the systematic bias caused by the uncertainty in convective core overshooting, element diffusion, mixing-length value, an...

We performed a detailed analysis of the main theoretical uncertainties affecting the age at the lithium depletion boundary (LDB). To do that we computed almost 12000 pre-main sequence models with mass in the range [0.06, 0.4] M_sun by varying input physics (nuclear reaction cross-sections, plasma electron screening, outer boundary conditions, equat...

Recent results by Bensby and collaborators on the ages of microlensed stars in the Galactic bulge have challenged the picture of an exclusively old stellar population. However, these age estimates have not been independently confirmed. In this paper we verify these results by means of a grid-based method and quantify the systematic biases that migh...

We study the impact on stellar age determination by means of grid-based techniques adopting asteroseismic constraints of the uncertainty in the radiative opacity, in the initial helium abundance, in the mixing-length value, in the convective core overshooting, and in the microscopic diffusion efficiency adopted in stellar model computations. We ext...

The p(p,$e^+\nu_e$)$^2$H reaction rate is an essential ingredient for theoretical computations of stellar models. In the past several values of the corresponding S-factor have been made available by different authors. Prompted by a recent evaluation of S(E), we analysed the effect of the adoption of different proton-proton reaction rates on stellar...

Context. The habitability of an exoplanet is assessed by determining the times at which its orbit lies in the circumstellar habita ble zone (HZ). This zone evolves with time following the stellar luminosity variation, which means that the time spent in the HZ depends on the evolution of the host star. Aims. We study the temporal evolution of the HZ...

STREGA (STRucture and Evolution of the GAlaxy) is a guaranteed time survey being performed at the VST (the ESO Very Large Telescope Survey Telescope) to map about 150 square degrees in the Galactic halo, in order to constrain the mechanisms of galactic formation and evolution. The survey is built as a 5 yr project, organized in two parts: a core pr...

We study the temporal evolution of the habitable zone (HZ) of low-mass stars - only due to stellar evolution - and evaluate the related uncertainties. These uncertainties are then compared with those due to the adoption of different climate models. We computed stellar evolutionary tracks from the pre-main sequence phase to the helium flash at the r...