Nucleosynthesis and molecular processes in the late stages of Stellar Evolution

    General
    Description

    Low- to intermediate-mass (M < 8 solar masses, Ms) stars represent the majority of stars in the Cosmos. They finish their lives on the Asymptotic Giant Branch (AGB) - just before they form planetary nebulae (PNe) - where they experience complex nucleosynthetic and molecular processes. AGB stars are important contributors to the enrichment of the interstellar medium where new stars/planets are born (including our own Early Solar System, ESS), and to the chemical evolution of stellar systems like globular clusters (GCs) and galaxies. In particular, the more massive (M > 4-5 Ms) AGB stars synthesize very different (radio)isotopes from those formed by lower mass AGB stars and Supernova detonations, as a consequence of different nucleosynthesis mechanisms. Evolved stars in the transition phase between AGB stars and PNe also form diverse organic compounds like PAHs, and fullerene and graphene molecular nanostructures, being a wonderful laboratory for Astrochemistry. On-going massive surveys like SDSS-IV/APOGEE-2 and the upcoming James Webb Space Telescope (JWST) represent a fundamental step forward to understand the nucleosynthesis and molecular processes in evolved stars. We aim to explore the nucleosynthesis of light and heavy (radio)isotopes in AGB stars and how they contribute to the ESS radioactive inventory as well as to the formation and evolution of GCs and galaxies. We also aim at understanding the top-down formation process of fullerene and graphene molecular nanostructures in evolved stars. Finally, it is intended to perform data mining with the Gaia satellite, in order to study the AGB- PNe evolutionary phase. In addition we aim to use the GALEX database to discover binary central stars in Galactic PNe.

    Principal investigator

    1. During 2020, we have published 37 papers in high-impact international refereed astronomical journals (including one invited review) and 2 papers in the Chemistry -Physics journal FNCN.

    2. Phosphorus-rich stars with an extremely peculiar chemical abundance pattern have been discovered for the first time, challenging the theoretical nucleosynthesis predictions.

    3. It was demonstrated that the P-rich star progenitors represent a new site for s-process nucleosynthesis, with important implications for the chemical evolution of our Galaxy.

    Related publications

    Disentangling the Galactic Halo with APOGEE. I. Chemical and Kinematical Investigation of Distinct Metal-poor Populations 2018ApJ...852...49H
    Disentangling the Galactic Halo with APOGEE. II. Chemical and Star Formation Histories for the Two Distinct Populations 2018ApJ...852...50F
    Binary stars in the Galactic thick disc 2018MNRAS.473.2984I
    Elemental Abundances of Kepler Objects of Interest in APOGEE. I. Two Distinct Orbital Period Regimes Inferred from Host Star Iron Abundances 2018AJ....155...68W
    C/O ratios in planetary nebulae with dual-dust chemistry from faint optical recombination lines 2018MNRAS.473.4476G
    Where does galactic dust come from? 2018MNRAS.473.4538G
    12C/13C isotopic ratios in red-giant stars of the open cluster NGC 6791 2018MNRAS.474.4810S
    The interaction of the halo around the butterfly planetary nebula NGC 650-1 with the interstellar medium 2018MNRAS.475..932R
    The First APOKASC Catalog of Kepler Dwarf and Subgiant Stars 2017ApJS..233...23S
    The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory 2017ApJS..233...25A
    C70 Fullerene charge-transfer interaction with alkylnaphthalenes, pinenes, and a diene 2017FNCN...25..505G
    Charge-transfer interaction between C60 fullerene and alkylnaphthalenes 2017FNCN...25..223G
    Target Selection for the SDSS-IV APOGEE-2 Survey 2017AJ....154..198Z
    Rubidium and zirconium abundances in massive Galactic asymptotic giant branch stars revisited 2017A&A...606A..20P
    Adding the s-Process Element Cerium to the APOGEE Survey: Identification and Characterization of Ce ii Lines in the H-band Spectral Window 2017ApJ...844..145C
    APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy 2017ApJ...845..162H
    The Apache Point Observatory Galactic Evolution Experiment (APOGEE) 2017AJ....154...94M
    Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns 2017ApJ...846L...2F
    The evolution of Galactic planetary nebula progenitors through the comparison of their nebular abundances with AGB yields 2017MNRAS.471.4648V
    Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe 2017AJ....154...28B
    The Correlation between Mixing Length and Metallicity on the Giant Branch: Implications for Ages in the Gaia Era 2017ApJ...840...17T
    Asymptotic giant branch and super-asymptotic giant branch stars: modelling dust production at solar metallicity 2017MNRAS.467.4431D
    Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way's radial metallicity gradient 2017A&A...600A..70A
    Two groups of red giants with distinct chemical abundances in the bulge globular cluster NGC 6553 through the eyes of APOGEE 2017MNRAS.465...19T
    Chemical tagging with APOGEE: discovery of a large population of N-rich stars in the inner Galaxy 2017MNRAS.465..501S
    Chemical Abundances of M-dwarfs from the APOGEE Survey. I. The Exoplanet Hosting Stars Kepler-138 and Kepler-186 2017ApJ...835..239S
    APOGEE chemical abundances of globular cluster giants in the inner Galaxy 2017MNRAS.466.1010S
    Galactic archaeology with asteroseismology and spectroscopy: Red giants observed by CoRoT and APOGEE 2017A&A...597A..30A
    Clear Evidence for the Presence of Second-generation Asymptotic Giant Branch Stars in Metal-poor Galactic Globular Clusters 2015ApJ...815L...4G
    Evidence for a metal-poor population in the inner Galactic bulge 2015A&A...584A..45S
    The SDSS-III APOGEE Spectral Line List for H-band Spectroscopy 2015ApJS..221...24S
    AGB stars in the SMC: evolution and dust properties based on Spitzer observations 2015MNRAS.454.4235D
    An Infrared Diffuse Circumstellar Band? The Unusual 1.5272 Micron DIB In the Red Square Nebula 2015ApJ...811..119Z
    Abundances, Stellar Parameters, and Spectra from the SDSS-III/APOGEE Survey 2015AJ....150..148H
    The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III 2015ApJS..219...12A
    High-resolution Imaging of NGC 2346 with GSAOI/GeMS: Disentangling the Planetary Nebula Molecular Structure to Understand Its Origin and Evolution 2015ApJ...808..115M
    Chemical Cartography with APOGEE: Metallicity Distribution Functions and the Chemical Structure of the Milky Way Disk 2015ApJ...808..132H
    The radial abundance gradient of chlorine in the Milky Way 2015MNRAS.452.1553E
    A test for asymptotic giant branch evolution theories: planetary nebulae in the Large Magellanic Cloud 2015MNRAS.452.3679V
    Constraint on the time variation of the fine-structure constant with the SDSS-III/BOSS DR12 quasar sample 2015MNRAS.452.4153A

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