Abstract Carbon, nitrogen and oxygen in stars bring valuable information for Galactic chemical evolution (GCE) modelling, stellar evolution and exoplanet studies. We have measured the 12 C abundance, the isotopic ratio 12 C/ 13 C and the 14 N abundance for 27 solar analogue stars and 55 solar twin stars, having both samples a wide range in isochrone age. 14 N and 14 N/ 15 N have been measured for 59 metal-rich solar twin stars that have a wide age coverture too. The three samples contain solar-type dwarfs belonging to the Galactic thin disc up to around 106 pc in distance. All samples stars are identified as stars hosting gaseous giant planets and stars without detected gaseous giant planets. Both isotopic ratios have been derived for ‘solar twins’ for the first time. In this work, we compile our main results on several abundance ratios involving C and N isotopes as a function of the isochrone age and metallicity.
Abstract. The initial mass function of the Galactic bulge can be obtained from Hubble Space Telescope luminosity functions if the statistics of binary stellar systems is well constrained. Such statistics can be estimated using gravitational microlensing effect, which is sensitive to the masses of lensing objects. Current microlensing surveys are sensitive to microlensing signals produced by low-mass stars in the bulge. We propose to search for and analyze microlensing events containing binary lens or binary source in light curves of large microlensing surveys, including low-mass, unresolved binaries. We implemented a fully-automated approach in the search and characterization of new and previously identified events. With the consideration of detection efficiency, the large statistics of binaries gives constraints for the binary fraction and mass-ratio distribution. In this work, methods and results for some events with well-separated bumps are presented.
Abstract . With the aim of exploring TESS metal-poor accreted star candidates, we calculated chemical abundances, dynamical properties, and ages of a sample of 30 stars. We found that our sample is dominated by metal-poor ([Fe/H] ≤ -0.7) old objects (ages ≥ 7 Gyrs), but we identified a fraction of apparently young objects (ages ≤ 7 Gyrs). The stars also have [ α /Fe] ≥ 0.2, and [Cu/Fe] ≤ 0. Finally, according to their dynamical properties, we concluded that the majority of our sample is composed of stars likely from the Gaia-Sausage-Enceladus progenitor (GES). Additionally, we explored the impact of incorporating asteroseismic information on age and chemical abundance calculations of metal-poor accreted stars for which TESS data is available. While we observe that the inclusion of seismic information significantly impacts the stellar ages obtained for our sample of stars, chemical abundances suffer a less significant effect in this study.
Abstract Classical barium (Ba) stars are red giants enriched in elements produced primarily by the slow neutron capture mechanism ( s -process). Their chemical peculiarities, attributable to mass-transfer events in binary system, are powerful tools to trace back their polluter sources, former thermally-pulsing asymptotic giant branch stars. In this contribution, we report results from a chemical analysis focused on tungsten (W, Z = 74) for a sample of 180 Ba giants, based on high-resolution spectra. The observed [W/Fe] ratios, which range from ∼ 0.0 to 2.0 dex, increase for lower metallicity regimes and strongly correlate with the s -process averaged abundances. By comparing the observational data set with predictions from the FRUITY and Monash nucleosynthesis models, we noticed that stars with high [W/hs] ratios may represent evidence for the operation of the intermediate neutron-capture process at metallicities close to solar.
Abstract The oldest stars in the Milky Way are expected to have a high density in the inner few kpc, spatially overlapping with the Galactic bulge. I will briefly summarise how to find the most metal-poor stars in this challenging region, and what their kinematics and chemistry are like. I specifically highlight the relevance of carbon-enhanced metal-poor (CEMP) stars.
Abstract. We obtained [X/Fe] ratios of 20 elements with high precision (0.01 - 0.02 dex) for a sample of 100 solar twins using Neural Networks (NN) and high quality spectra from HARPS. The abundances were corrected by the Galactic Chemical Evolution (GCE) and studied along with the condensation temperature (T cond ) of the elements, to verify how distinct the Sun is compared to the solar twins. We concluded that the Sun is peculiar, being more depleted in refractories than 89% of the solar twins, with a significance of ∼9σ, which may be a signature of planetary systems like ours. The results presented here are part of Martos et al., (2025).
Abstract Massive stars play a crucial role in the chemo-dynamical evolution of the Milky Way, influencing its circumstellar and interstellar medium and being the primary source of heavy-element production. Despite the importance of this stellar population, existing discrepancies between observational data and theoretical models of massive stars have questioned our understanding of these objects. Studying statistically significant and homogeneous volume-limited samples of massive stars is key to alleviating this situation and to narrow down those discrepancies. The IACOB high-resolution spectroscopic database, with almost 3000 sources and a high degree of completeness, allows us to study the physical and chemical properties of our massive neighbors. Key findings from the analysis of ∼ 900 O-type stars and blue supergiants are presented, providing new empirical constraints for new evolutionary model computations.
Abstract The Subaru Prime Focus Spectrograph (PFS) will dedicate approximately 130 nights to study the structure and evolution of galaxies in the Local Group. This galactic archaeological survey will have three pillars: (1) We will determine whether the mass density profiles of dwarf galaxies are consistent with cusps, as expected for cold dark matter, or cores, as expected from alternative dark matter theories or baryonic feedback. We will deduce the density profiles as a function of radius from Jeans modeling of the full line-of-sight velocity distributions for six dwarf galaxies. Our total sample will consist of 40,000 member stars. (2) From measurements of [ α /Fe] abundance ratios, we will learn the difference in assembly history of the two most massive galaxies in the Local Group: M31 and the Milky Way. We will observe 30,000 member stars over 45 square degrees of M31’s halo and outer disk. (3) We will uncover how the most fragile part of the Milky Way responded to accretion events in the distant past (like Gaia–Enceladus Sausage) and in recent history (like Sagittarius). To support this study, PFS will provide velocities and metallicities—from which we will deduce ages—for tens of thousands of stars out to a Galactocentric distance of 30 kpc.
Abstract Massive late O- and early B-type stars are ideal indicators for present-day elemental abundances in star-forming regions in the solar neighbourhood and throughout wide parts of the Milky Way disk. They complement other classical indicators such as emission line spectra of H ii regions while providing abundance data of high accuracy and precision. An overview of the progress made in deriving abundances for a wide range of chemical species from spectra in the UV, optical, and near-IR domains is given. Results for OB-star populations in the Milky Way are discussed. These provide observational present-day boundary conditions for the study of Galactochemical evolution and point to a birthplace of the solar system at a galactocentric radius of 5 to 6 kpc with subsequent migration to its current location.
Abstract The James Webb Space Telescope ( JWST ) has proven to be an effective tool for identifying and analyzing multiple stellar populations in globular clusters, with sensitivity extending to the hydrogen-burning limit. Here we present a kinematic analysis of distinct stellar populations in 47 Tucanae, examining their velocity dispersion and anisotropy profiles from the core to approximately 10 half-light radii ( R h ). Our analysis reveals contrasting kinematic behaviors: first-generation (1G) stars display isotropic distributions, while second-generation (2G) stars exhibit pronounced radial anisotropy. These findings are consistent with simulations that model the dynamical evolution of clusters where 2G stars begin more centrally concentrated than 1G stars. This work presents the first measurement of energy equipartition between different stellar populations in 47 Tucanae. Within the studied radial range (approximately 2-4 R h ), both populations show limited energy equipartition. The most pronounced distinctions between generations appear in the tangential velocity component, where 2G stars demonstrate enhanced energy equipartition compared to their 1G counterparts. The radial velocity component shows more complex behavior, with generational differences showing significant radial dependence.
Abstract Low-mass and low-metallicity Aymptotic Giant Branch (AGB) stars contribute to the chemical evolution of heavy elements through slow (s) and intermediate (i) neutron-capture processes. During AGB stars evolution the i-process occur when protons are mixed in a convective helium burning zone often termed as the proton ingestion event (PIE), and the s-process takes place in the interiors of Thermally-Pulsing Asymptotic Giant Branch (TP-AGB) stars. CEMP (s and r/s) stars are main-sequence and giants that receive from their evolved binary companions material exposed to s- and i-process nucleosynthesis. As post-interacting binaries, these stars figure as powerful tracers of s- and i-process nucleosynthesis, evolution of binary systems and mechanisms of mass-transfer. Some highlights of results obtained from high-resolution spectroscopic studies of a sample of CEMP-s and CEMP-r/s stars are discussed in the light of observational evidence for the operation of s- and i- neutron-capture processes.
Abstract We developed a chemical evolution model that incorporates the mass distribution in the bulge and disc to determine the radial dependence of the time-scale in the Galaxy. The model was used to test a scenario in which the bulge forms inside-out. The model successfully reproduces several key features of the data: the spread in the [ α /Fe] versus [Fe/H] relation, the shape of the metallicity distribution function across different regions of the bulge, the [Fe/H] radial gradient within the bulge, the age-metallicity relationship and the evolution of [ α /Fe] with age. The findings suggest a scenario in which most of the bulge stars formed before the development of the boxy/peanut X-shaped bar structure. Consequently, the classical origin of the Galactic bulge cannot be excluded, and this scenario provides a plausible explanation for the observed chemical properties of the bulge.
Abstract The ΛCDM model predicts a hierarchical formation for galaxies. Many substructures were found in the Galactic halo, identified as clumps in kinematic spaces. If they also feature different chemical properties, they are then associated to independent merger debris. Our aim is to explore to what extent different clumps in the energy-angular momentum space ( E−L z ) with different metallicity distribution functions (MDF) trace the accretion history of the Galaxy. By means of N-body simulations, we confirm that accreted stars from a massive merger redistribute in a wide range of E and L z , due to dynamical friction, thus not being associated to a single clump. Since satellite stars with different metallicities can be deposited in different regions of the E−L z space, a single accretion can manifest with different MDFs. This method can bias the merger tree of the Galaxy towards increasing the number of accretions and decreasing the masses of the progenitor galaxies.
Abstract Gaia’s precise astrometric and photometric data have transformed our understanding of blue straggler stars (BSS) by facilitating their accurate identification, distance measurement, and spatial mapping across various environments. This has enabled larger and more detailed samples to be used to study their origins, formation mechanisms, and role in stellar evolution. Overall, Gaia’s capabilities mark a significant leap forward in unraveling the mysteries of blue stragglers. In this poster, we present how the large scale surveys era has marked a transformative period in our understanding of BSS, providing deeper insights into their properties, origins, and the role they play in stellar evolution and cluster dynamics.
Abstract Stellar evolution studies of low-to-intermediate mass stars are hindered by the lack of a solid link that connects their initial and final properties. This problem can be resolved for stars that are members of star clusters and at the final stages of their evolution. In such cases, we can estimate their final properties from direct measurements and obtain the necessary information for the properties of their progenitors from independent cluster studies. Here, we focus on the study of planetary nebulae that are confirmed members of Galactic open star clusters. These rare instances provide us with a new additional sample of data, which contributes to the fundamental initial-to-final mass relation (IFMR). We examine the quality of this contribution and assess the efficacy of our method, showing that our approach is very promising with already significant initial results. Our data generally confirm the latest IFMR trends, filling important gaps in the process.
Abstract In this work, we study the relationship of effective temperature with mean magnetic field and Rossby number for M-dwarf stars. We compiled a sample of 163 field stars and 62 stars from the Pleiades young open cluster. We found no clear relation between effective temperature and stellar activity for partially convective field stars, although for Pleiades stars there is a trend, with cooler stars being more active. For fully-convective field stars, we note a large scatter in the relation between effective temperature and activity. Despite being much older, we found that the fully-convective field stars reach higher activity levels than the Pleiades partially convective stars.
Abstract We present the final result of an applied geometry research as an algorithm for interpolation of in N -dimensional sparse grids. The method is based on divide and conquer approach and a “golden rule” chosen for optimization of the problem in specific and general terms, showing good results in a much shorter computer time. We present the results from its application to the problem of estimating age and mass of stelar clusters.
Abstract In this short proceeding I visually highlight the immense improvement in sample size, survey volume, and precision that Galactic archaeology has experienced in the past 10 years.
Abstract The Galactic center is a unique region in the center of the Milky Way, with the Nuclear Star Cluster (NSC) and the Nuclear Stellar Disk (NSD) embedded in the Central Molecular Zone. A promising approach to study these regions, is the analysis of abundance trends of a range of elements with different evolutionary timescales. Using high-resolution near-infrared spectroscopy, accurate elemental abundances can now be derived in the NSC and NSD. A powerful tool is to compare the trends from these populations with those from inner-bulge and thick-disk stars analyzed with the same methodology. In a few papers we have pioneered this approach finding enhanced alpha-element trends, indicating a high star formation rate, and similarities between the NSC and inner bulge, challenging previous models of recent dominant starbursts. These findings provide new insights into the formation history of the Milky Way’s central regions and emphasize the need for further high-resolution spectroscopic studies.
Abstract Despite being a powerful tool, the synthesis of stellar population models requires many ingredients, all of them involving assumptions and uncertainties. In particular the libraries of stellar spectra are crucial ingredients. In this work we present a new empirical spectral library, that will push the limits for modeling young, low metallicity stellar systems.
