Searcharxiv⌕ Search

arXiv subjects

Laura Magrini

Publications and source records attributed to Laura Magrini.

At least 19 recordsLinked to original sources
arXiv2026

Tracing the early Milky Way thin disc with the Gaia-ESO Survey

The origin of metal-poor stars on thin-disc-like orbits remains an open question in Galactic archaeology and provides important constraints on the earliest phases of Milky Way disc formation. We aim to identify and characterise metal-poor stars with thin-disc-like kinematics observed in the Gaia-ESO Survey, using Gaia DR3 orbital parameters, spectroscopic information, isochrone ages, and detailed chemical abundances. Out of 1784 turn-off stars, we identify one metal-poor candidate with [Fe/H] = -1.38 on a dynamically cold, prograde orbit, with low eccentricity, high azimuthal velocity ($V_\phi$ approximately 220 km/s), large angular momentum and low vertical action. Chemically, however, it is clearly distinct from the canonical thin disc: it is $\alpha$-enhanced, with [Mg/Fe] = +0.58 and [$\alpha$/Fe] = +0.48, shows a low [Y/Mg] = -0.58 ratio, and lies on the metal-poor sequence in the [Al/Fe]-[Mg/Mn] plane. The star also has an old age estimate, with a most probable value of about 10.2 Gyr. Its properties suggest that it is not a typical member of the canonical thin disc. Instead, it may be associated with the old thin disc, the metal-weak thick disc, or prograde halo-related populations. This object provides a useful benchmark for studying early metal-poor populations on disc-like orbits.

astro-ph.GA↗
arXiv2026

HRMOS: a very high-resolution, multi-object spectrograph for the ESO VLT

HRMOS (High-Resolution Multi-Object Spectrograph) is a proposed new instrument for the ESO Very Large Telescope (VLT) developed in the context of the ESO VLT Beyond 2030 call. It is designed to fill a unique and currently unoccupied region in the observational landscape: the combination of very high spectral resolution (R=80,000) with multi-object capability (50-60 simultaneous targets), a radial-velocity (RV) precision of 10m/s, and coverage of three key spectral windows (385-421nm, 480-522nm, 623-677nm). Scientifically, HRMOS will address a rich portfolio of high-priority astrophysical questions spanning from f giant exoplanet formation, to nucleocosmochronology and constraints on cosmological parameter, to probing hierarchical galaxy assembly outside the Milky Way. The instrument is based on a modular approach and it consists in four primary subsystems, the Front End with a hybrid fiber-positioning and atmospheric dispersion correction (ADC) architecture, the Fiber Link with double-scrambling and the image slicers, three spectrographs based on volume phase holographic (VPH) gratings covering the three spectral ranges and a Calibration Unit.

astro-ph.IM↗
arXiv2026

HRMOS: A High-Resolution Multi-Object Spectrograph for the VLT

This White Paper presents the scientific rationale and instrument concept for HRMOS (High-Resolution Multi-Object Spectrograph), a next-generation instrument proposed for the ESO Very Large Telescope within the VLT 2030 roadmap. Current and planned facilities offer either multi-object spectroscopy or ultra-high spectral resolution, but not both. HRMOS fills this gap by combining very high spectral resolution, multi-object capability, and radial-velocity stability, enabling transformative studies in Galactic and extragalactic astrophysics. The baseline design provides a resolving power of R = 80000, radial-velocity precision of 10 m s-1 (goal: 5 m s-1), simultaneous observations of 50-60 targets, and broad optical coverage down to 385 nm. These capabilities enable precise measurements of elemental abundances, isotopic ratios, line profiles, and radial velocities for large stellar samples, including crowded fields, star clusters, the Galactic bulge, and nearby dwarf galaxies. HRMOS will address key questions on the age of the oldest stellar populations through nucleocosmochronology, the formation and survival of planetary systems, the assembly history of the Milky Way and satellites, the origin of the heaviest elements, stellar evolution, and the chemical and dynamical properties of the interstellar and circumgalactic medium. It will bridge large spectroscopic surveys and the next generation of extremely large telescopes, with strong synergies with 4MOST, Gaia, TESS, PLATO, the proposed Haydn mission, and future ELT instruments. Building on VLT/FLAMES heritage, HRMOS represents a strategic investment for European astronomy in the 2030s.

astro-ph.IM↗
arXiv2026

WST -- Wide-field Spectroscopic Telescope: The Next Leap in Wide-field Spectroscopy

The Wide-field Spectroscopic Telescope (WST) is a concept for a dedicated 12-m spectroscopic survey facility designed to address some of the most important questions in astrophysics in the 2040s. The WST will provide unprecedented spectroscopic survey capabilities by operating simultaneously over a 2-degree diameter field of view with 54 low-resolution spectrographs fed by 30,000 fibres, 8-16 high-resolution spectrographs fed by 2,000 fibres, and a large panoramic low-resolution integral-field spectrograph. Supported by Horizon Europe, the concept study has refined the science cases, facility architecture, operations model, sustainability strategy, and technology roadmap. The resulting reference design demonstrates that the WST is both scientifically transformative and technically feasible, while identifying the developments required to mitigate the remaining risks. The WST is designed as an ESO flagship facility for the post-ELT construction era and a key spectroscopic complement to the major imaging, time-domain, and multi-messenger facilities of the coming decades.

astro-ph.IM↗
arXiv2026

The nucleosynthesis of Ba in the Early Universe. Constraints from elemental abundances and isotopic ratios

The [Ba/Eu] abundance ratio is commonly adopted as a tracer of the relative contributions of the slow (s) and rapid (r) neutron-capture processes. However, at [Fe/H] < -2 dex, Ba can be produced efficiently by both processes, rendering [Ba/Eu] non-deterministic. We propose to use barium isotopic ratio from the fitting of resonance Ba line profiles affected by hyperfine splitting. This approach requires precise atomic and stellar parameters, together with advanced spectral modelling, which, so far, remained insufficiently validated. We aim to provide a robust prescription of line-profile modelling for a reliable determination of the s- and r-processes fractions of barium in ordinary and peculiar stars. We assess the performance of 1D LTE and 1D non-LTE synthesis, and 3D non-LTE abundance corrections to model Ba lines. Alongside barium abundances and its isotopic ratios, we determine Eu and other neutron-capture element abundances to validate the method in the Titans metal-poor benchmark stars. The observational results are compared with the predictions of stochastic Galactic chemical evolution models that account the inhomogeneous mixing in the early times. We find that 1D LTE and 3D non-LTE Ba abundance determinations are equivalent, whereas the 1D non-LTE approach leads to systematic underestimations. These underestimations bias isotopic fractions toward higher r-process contributions. The inferred s- and r-process fractions demonstrate that [Ba/Eu] alone is an ambiguous tracer for ordinary stars within the range -0.8 < [Ba/Eu] < 0 dex. The comparison of our set of models, both for the proto-Milky Way halo and for Gaia-Enceladus galaxy is used to put constraints on the production of Ba at low [Fe/H], especially evaluating the role of rotating massive stars. The method here developed can be applied with confidence to both ordinary stars and peculiar stars enhanced in barium.

astro-ph.SR↗
arXiv2026

Observational Signatures and Constraints on the Intermediate Neutron-Capture Process. The Case of the CEMP star TYC 6044-714-1 (RAVE J094921.8-161722)

Observational abundances of CEMP stars with patterns in between those produced by the rapid and slow nucleosynthesis processes (CEMP-rs stars) are currently invoked as evidence of synthesis via the intermediate process in the early AGB evolutionary phase of metal-poor low mass stars. Nevertheless, discriminating between r+s- and i-process hypotheses requires high-precision abundances obtained through advanced spectral modelling techniques. Theoretical models of the i-process have become more robust, incorporating refined stellar modelling and nuclear reaction physics, providing ranges of probable elemental abundances and isotopic ratios predictions to be confronted with observational determinations. We performed a new analysis of a high resolution and high S/N UVES spectrum of TYC 6044-714-1. We derived accurate effective temperature and highly precise atmospheric parameters, element abundances, and isotopic ratios using state-of-the-art 1D non-LTE and 3D non-LTE spectral line modelling. Using the latest AGB nucleosynthesis models, we assessed the possibility of the i-process to act aside the s-process. We find that TYC~6044-714-1 was likely born as a normal in-situ halo star about 13 Gyr ago, pre-enriched by the r-process through a standard Galactic chemical-evolution pathway. The s+r model provides the best overall reproduction of the observed heavy-element abundance pattern and Ba isotopic ratios, yielding excellent agreement across all three s-process peaks. While i+s+r models with increasing overshooting efficiency improve the fit for specific elements, they do not consistently reproduce the full abundance pattern. The i+s+r models require extreme and physically implausible conditions, and predict s-process Ba fractions inconsistent with those inferred from isotopic ratios of the 4934 \AA\ resonance line. We conclude that the pure s+r scenario is the most plausible explanation.

astro-ph.SR↗
arXiv2025

Mapping the Ages of Stars with Chemistry

Chemical clocks, based on age-sensitive stellar abundance ratios, offer a powerful and scalable approach to reconstruct the formation history of the Milky Way. This white paper outlines how wide-field, high-resolution spectroscopy can transform chemical clocks into precise and broadly applicable stellar age estimators when combined with astrometry and asteroseismology. We summarize the current limitations, including calibration across Galactic environments and the impact of internal stellar evolution, and define the observational requirements needed to overcome them. The Wide-field Spectroscopic Telescope (WST), with its large field of view, high multiplex, and broad wavelength coverage at high spectral resolution, is uniquely suited to deliver the homogeneous datasets required to map the age structure of the Galaxy at unprecedented scale. Such a capability will enable decisive progress in Galactic archaeology and stellar evolution studies.

astro-ph.GA↗
arXiv2025

Deep chemical tagging -- Identifying open clusters and moving groups in chemical space with graph attention networks

Reconstructing the formation history of the Milky Way is hindered by stellar migration, which erases kinematic birth signatures. In contrast, stellar chemical abundances remain stable and can be used to trace stars back to their birth environments through chemical tagging. This study aims to improve chemical tagging by developing a method that leverages kinematic and age information to enhance clustering in chemical space, while remaining grounded in chemistry. We implement a graph attention auto-encoder that encodes stars as nodes with chemical features and connects them via edges based on orbital similarity and age. The network learns an ``informed'' chemical space that accentuates coherent groupings.Applied to $\sim$47,000 APOGEE thin disk stars, the method identifies 282 stellar groups. Among them, five out of six open clusters are successfully recovered. Other groups align with the known moving groups Arch/Hat, Sirius, Hyades, and Hercules. Our approach enables chemically grounded yet kinematically and age informed chemical tagging. It significantly improves the identification of coherent stellar populations, offering a framework for future large-scale stellar archaeology efforts.

astro-ph.GA↗
arXiv2025

Barium isotopic ratios in metal-poor stars: calibrating the method with globular clusters

Identifying the nucleosynthesis processes behind heavy-element enrichment in stellar atmospheres is challenging. It typically relies on comparing observed abundance-to-iron ratios with theoretical predictions relative to the Sun, but this method is prone to uncertainty due to limitations of classical 1D hydrostatic models. One promising but still underexplored approach is to measure the isotopic composition of stellar atmospheres by focusing on elements that have both slow (s)-process and rapid (r)-process contributions. While the study of total elemental abundances offers a simplified view, isotopic ratios are directly linked to the underlying nucleosynthesis processes. Our aim is to provide a reliable method for quantifying the contributions of the s- and r-processes to barium in stellar atmospheres. This is achieved by determining barium isotopic ratios using 1D atmospheric models in combination with a carefully calibrated microturbulence, based on the comparison between subordinate and resonance Ba lines. In this initial study, we use member stars of the globular cluster NGC 6752 to calibrate the microturbulence ($v_{mic}$) value for both subordinate and resonance barium lines across different stellar evolutionary stages. This allows us to provide a reliable estimate of $v_{mic}$ that can be applied to accurately determine barium abundances and isotopic ratios in stars ranging from the main sequence to the upper red giant branch. The $v_{mic}$ scale adapted for barium subordinate lines is consistent with that derived from 3D model atmospheres, and thus the $T_{\mathrm{eff}}$-log $g$ dependent relations of the later can be used safely. The $v_{mic}$ for the resonance line at $\lambda$4934 Angstrom -- for the determination of the isotopic ratio -- is higher, and depends on the equivalent width (EW). We provide calibrated relations between $v_{mic}$ and EW for measuring isotopic ratios.

astro-ph.SR↗
arXiv2025

How homogeneous was the chemical enrichment of the Milky Way 13 gigayears ago?

We reanalyze the chemical composition of the metal-poorest tail of the Galactic halo using highly accurate atmospheric parameters Giribaldi et al. (2021, 2023) and cutting-edge 3D NLTE models Amarsi et al (2018). Most [Mg/Fe] versus [Fe/H] diagrams in the literature exhibit significant scatter at [Fe/H] $\lesssim -2$ dex, often interpreted as evidence of inhomogeneous enrichment during the early phases of galaxy evolution Rossi et al. (2021). However, our analysis of observational data reveals that in the range $-3.5 <$ [Fe/H] $< -2$ dex, the [Mg/Fe] versus [Fe/H] distribution is relatively narrow. This finding suggests a low degree of stochastic enrichment in magnesium during these epochs in the Milky Way halo.

astro-ph.GA↗
arXiv2025

The metal-poorest tail of the Galactic halo: hypothesis on its origin from precise spectral analysis

The origin of the Galactic halo is one of the fundamental topics linking the study of galaxy formation and evolution to cosmology. We aim at deriving precise and accurate stellar parameters, Mg abundances, and ages for a sample of metal-poor stars with [Fe/H] $<$ -2 dex from high signal-to-noise and high resolution spectra. We derive effective temperatures from H$\alpha$ profiles using three-dimensional non local thermodynamic equilibrium (3D NLTE) models, and surface gravities and ages from isochrone fitting based on Gaia data. Iron abundances were derived in one-dimensional (1D) NLTE, while Mg abundances were derived in 1D LTE, 1D NLTE, 3D LTE, and 3D NLTE to show the increasing level of accuracy. The stars show a tight trend in the [Mg/Fe] vs [Fe/H] plane with a knee at [Fe/H]$\sim$ -2.8 dex, which indicates a low level of stochasticity. Their location in the Lindblad diagram confirms their belonging to the Galactic halo, but does not show a distinct clustering that might be expected for a merger with a single low-mass galaxy. Comparison with chemical evolution models is also not definitive on whether the sample stars were born in-situ or in accreted low-mass galaxy mergers. We find two plausible explanations for the chemical sequence traced by the stars in the [Mg/Fe] vs [Fe/H] plane. One is that the sample stars originated in the already formed Milky Way, which at that time (12.5 Gyr ago) was already the main galaxy of its Local Group surroundings. Another one is that the sample stars originated in several small galaxies with similar properties, which later merged with the Galaxy. Only accurate spectroscopic analysis such as that done here can reveal trustworthy chemical diagrams required to observe the traces of the Galaxy evolution. Other elements are required to discern between the two hypotheses.

astro-ph.GA↗
arXiv2024

Modelling chemical clocks -- Theoretical evidences of the space and time evolution of [s/alpha] in the Galactic disc with Gaia-ESO survey

Chemical clocks based on [s-process elements/alpha-elements] ratios are widely used to estimate ages of Galactic stellar populations. However, the [s/alpha] vs. age relations are not universal, varying with metallicity, location in the Galactic disc, and specific s-process elements. Current Galactic chemical evolution models struggle to reproduce the observed [s/alpha] increase at young ages. We provide chemical evolution models for the Milky Way disc to identify the conditions required to reproduce the observed [s/H], [s/Fe], and [s/alpha] vs. age relations. We adopt a multi-zone chemical evolution model including state-of-the-art nucleosynthesis prescriptions for neutron-capture elements (AGB stars, rotating massive stars, neutron star mergers, magneto-driven supernovae). We explore variations in gas infall, AGB yield dependencies on progenitor stars, and rotational velocity distributions for massive stars. Results are compared with open cluster data from the Gaia-ESO survey. A three-infall scenario for disc formation captures the rise of [s/alpha] with age in the outer regions but fails in the inner ones, especially for second s-process peak elements. Ba production in the last 3 Gyr of chemical evolution would need to increase by half to match observations. S-process contributions from low-mass AGB stars improve predictions but require increases not supported by nucleosynthesis calculations, even with potential i-process contribution. Variations in the metallicity dependence of AGB yields show inconsistent effects across elements. Distributions of massive star rotational velocities fail to improve results due to balanced effects on elements. We confirm that there is no single relationship [s/alpha] vs. age, but that it varies along the MW disc. Current prescriptions for neutron-capture element yields cannot fully capture the complexity of evolution, particularly in the inner disc.

astro-ph.GA↗
arXiv2024

Inferring stellar parameters and their uncertainties from high-resolution spectroscopy using invertible neural networks

Context: New spectroscopic surveys will increase the number of astronomical objects requiring characterization by over tenfold.. Machine learning tools are required to address this data deluge in a fast and accurate fashion. Most machine learning algorithms can not estimate error directly, making them unsuitable for reliable science. Aims: We aim to train a supervised deep-learning algorithm tailored for high-resolution observational stellar spectra. This algorithm accurately infer precise estimates while providing coherent estimates of uncertainties by leveraging information from both the neural network and the spectra. Methods: We train a conditional Invertible Neural Network (cINN) on observational spectroscopic data obtained from the GIRAFFE spectrograph (HR10 and HR21 setups) within the Gaia-ESO survey. A key features of cINN is its ability to produce the Bayesian posterior distribution of parameters for each spectrum. By analyzing this distribution, we inferred parameters and their uncertainties. Several tests have been applied to study how parameters and errors are estimated. Results: We achieved an accuracy of 28K in $T_{\text{eff}}$, 0.06 dex in $\log g$, 0.03 dex in $[\text{Fe/H}]$, and between 0.05 dex and 0.17 dex for the other abundances for high quality spectra. Accuracy remains stable with low signal-to-noise ratio spectra. The uncertainties obtained are well within the same order of magnitude. The network accurately reproduces astrophysical relationships both on the scale of the Milky Way and within smaller star clusters. We created a table containing the new parameters generated by our cINN. Conclusion: This neural network represents a compelling proposition for future astronomical surveys. These coherent derived uncertainties make it possible to reuse these estimates in other works as Bayesian priors and thus present a solid basis for future work.

astro-ph.GA↗
arXiv2024

Mapping radial abundance gradients with Gaia-ESO open clusters: Evidence of recent gas accretion in the Milky Way disk

Context. Recent evidences from spectroscopic surveys point towards the presence of a metal-poor, young stellar population in the chemical thin disk. In this context, the investigation of the spatial distribution and time evolution of precise, unbiased abundances is fundamental to disentangle the scenarios of evolution of the Galaxy. Aims. We study the evolution of abundance gradients in the Milky Way by taking advantage of a large sample of open clusters, which are among the best tracers for this purpose. In particular, we use data from the last release of the Gaia-ESO survey. Methods. We perform careful selection of open cluster stars excluding those that may be affected by biases in spectral analysis. The cleaned open clusters sample is compared with detailed chemical evolution models for the Milky Way, using well tested stellar yields and prescription for radial migration. Different scenarios of Galaxy evolution are tested to explain the data, i.e. the two-infall and the three-infall frameworks, suggesting that the chemical thin disk is formed by one or two subsequent gas accretion episodes, respectively. Results. With the performed selection in cluster stars, we still find a metallicity decrease between intermediate age (1<Age/Gyr<3) and young (Age<1Gyr) open clusters. This decrease cannot be explained in the context of the two-infall scenario, even by accounting for the effect of migration and yield prescriptions. The three-infall model, with its late gas accretion in the last 3 Gyr, can explain the low metallic content in young clusters. However, we invoke a milder metal dilution relative to previous findings. Conclusions. To explain the observed low metallic content in young clusters, we propose that a late gas accretion episode triggering metal dilution should have taken place, extending the framework of the three-infall model for the first time to the entire Galactic disk.

astro-ph.GA↗
arXiv2024

WST -- Widefield Spectroscopic Telescope: Motivation, science drivers and top-level requirements for a new dedicated facility

In this paper, we describe the wide-field spectroscopic survey telescope (WST) project. WST is a 12-metre wide-field spectroscopic survey telescope with simultaneous operation of a large field-of-view (3 sq. degree), high-multiplex (20,000) multi-object spectrograph (MOS), with both a low and high-resolution modes, and a giant 3x3 arcmin2 integral field spectrograph (IFS). In scientific capability, these specifications place WST far ahead of existing and planned facilities. In only 5 years of operation, the MOS would target 250 million galaxies and 25 million stars at low spectral resolution, plus 2 million stars at high resolution. Without need for pre-imaged targets, the IFS would deliver 4 billion spectra offering many serendipitous discoveries. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work in synergy with future ground and space-based facilities. We show how it can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; the origin of stars and planets; and time domain and multi-messenger astrophysics. WST's uniquely rich dataset may yield unforeseen discoveries in many of these areas. The telescope and instruments are designed as an integrated system and will mostly use existing technology, with the aim to minimise the carbon footprint and environmental impact. We will propose WST as the next European Southern Observatory (ESO) project after completion of the 39-metre ELT.

astro-ph.IM↗
arXiv2023

HRMOS White Paper: Science Motivation

The High-Resolution Multi-Object Spectrograph (HRMOS) is a facility instrument that we plan to propose for the Very Large Telescope (VLT) of the European Southern Observatory (ESO), following the initial presentation at the VLT 2030 workshop held at ESO in June 2019. HRMOS provides a combination of capabilities that are essential to carry out breakthrough science across a broad range of active research areas from stellar astrophysics and exoplanet studies to Galactic and Local Group archaeology. HRMOS fills a gap in capabilities amongst the landscape of future instrumentation planned for the next decade. The key characteristics of HRMOS will be high spectral resolution (R = 60000 - 80000) combined with multi-object (20-100) capabilities and long term stability that will provide excellent radial velocity precision and accuracy (10m/s). Initial designs predict that a SNR~100 will be achievable in about one hour for a star with mag(AB) = 15, while with the same exposure time a SNR~ 30 will be reached for a star with mag(AB) = 17. The combination of high resolution and multiplexing with wavelength coverage extending to relatively blue wavelengths (down to 380\,nm), makes HRMOS a spectrograph that will push the boundaries of our knowledge and that is envisioned as a workhorse instrument in the future. The science cases presented in this White Paper include topics and ideas developed by the Core Science Team with the contributions from the astronomical community, also through the wide participation in the first HRMOS Workshop (https://indico.ict.inaf.it/event/1547/) that took place in Firenze (Italy) in October 2021.

astro-ph.IM↗
arXiv2023

The discovery space of ELT-ANDES. Stars and stellar populations

The ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is the optical and near-infrared high-resolution echelle spectrograph envisioned for the European Extremely Large Telescope (ELT). We present a selection of science cases, supported by new calculations and simulations, where ANDES could enable major advances in the fields of stars and stellar populations. We focus on three key areas, including the physics of stellar atmospheres, structure, and evolution; stars of the Milky Way, Local Group, and beyond; and the star-planet connection. The key features of ANDES are its wide wavelength coverage at high spectral resolution and its access to the large collecting area of the ELT. These features position ANDES to address the most compelling and potentially transformative science questions in stellar astrophysics of the decades ahead, including questions which cannot be anticipated today.

astro-ph.IM↗
arXiv2023

The role of radial migration in open cluster and field star populations with Gaia dr3

The survival time of a star cluster depends on its total mass, density, and thus size, as well as on the environment in which it was born and in which lies. Its dynamical evolution is influenced by various factors such as gravitational effects of the Galactic bar, spiral structures, and molecular clouds. Overall, the factors that determine the longevity of a cluster are complex and not fully understood. This study aims to investigate if open clusters and field stars respond differently to the perturbations that cause radial migration. In particular, we aim at understanding the nature of the oldest surviving clusters. We compared the time evolution of the kinematic properties of two Gaia DR3 samples: the first sample is composed of $\sim$40 open clusters and the second one of $\sim$66,000 MSTO field stars. Both selected samples are composed of stars selected with the same quality criterion, belonging to the thin disc, in a similar metallicity range, located in the same Galactocentric region [7.5-9 kpc] and with ages >1 Gyr. We performed a statistical analysis comparing the properties of the samples of field stars and of open clusters. A qualitative comparison of kinematic and orbital properties reveals that clusters younger than 2-3 Gyr are more resistant to perturbations than field stars and they move along quasi-circular orbits. Conversely, clusters older than approximately 3 Gyr have more eccentric and inclined orbits than isolated stars in the same age range. Such orbits lead them to reach higher elevations on the Galactic plane, maximising their probability to survive several Gyr longer. A formal statistical analysis reveals that there are differences among the time evolution of most of the kinematic and orbital properties of field stars and open clusters. Our results suggest that oldest survived clusters are usually more massive and move on orbits with higher eccentricity.

astro-ph.GA↗