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

    On the alumina dust production in the winds of O-rich asymptotic giant branch stars 2014MNRAS.441.1115D
    Chemical abundances in Galactic planetary nebulae with Spitzer spectra 2014A&A...567A..12G
    Dissecting the Spitzer colour-magnitude diagrams of extreme Large Magellanic Cloud asymptotic giant branch stars 2014MNRAS.442L..38D
    Circumstellar effects on the Rb abundances in O-rich AGB stars 2014A&A...564L...4Z
    Single Rotating Stars and the Formation of Bipolar Planetary Nebula 2014ApJ...783...74G
    The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment 2014ApJS..211...17A
    Far infrared (terahertz) spectroscopy of a series of polycyclic aromatic hydrocarbons and application to structure interpretation of asphaltenes and related compounds
    Dust Around R Coronae Borealis Stars. II. Infrared Emission Features in an H-poor Environment 2013ApJ...773..107G
    Infrared spectroscopy of fullerene C60/anthracene adducts 2013MNRAS.434..415G
    Target Selection for the Apache Point Observatory Galactic Evolution Experiment (APOGEE) 2013AJ....146...81Z
    Hot bottom burning and s-process nucleosynthesis in massive AGB stars at the beginning of the thermally-pulsing phase 2013A&A...555L...3G
    The changing nebula around the hot R Coronae Borealis star DY Centauri 2013MNRAS.431..159K
    Photolytic Decomposition of Hydrogenated C70: C70H38 and C70D38
    Kinetic Isotope Effects on the Photolysis of C60H18 and C60D18
    Perdeuterofulleranes: Synthesis and Properties of C70D38 and C70H38
    Synthesis and FT-IR Spectroscopy of Perdeuterofullerane: C60D36 Evidences of Isotope Effect in the Stability of C60D36
    Low and High Temperature Infrared Spectroscopy of C60 and C70 Fullerenes
    A Simple Synthesis of C60H18 from C60 Fullerene and Hydrogen Iodide
    Characterization of Hydrogenated Fullerene Mixture of C60Hx and C70Hx
    Determination of the Integrated Molar Absorptivity and Molar Extinction Coefficient of Hydrogenated Fullerenes
    On the Radical Anion Spectra of Fullerenes C-60 and C-70
    Far- and mid-infrared spectroscopy of complex organic matter of astrochemical interest: coal, heavy petroleum fractions and asphaltenes 2013MNRAS.429.3025C
    Diffuse interstellar bands in fullerene planetary nebulae: the fullerenes - diffuse interstellar bands connection 2013A&A...550L...6G
    Synthesis of polyphenylacetylene by radiation-induced polymerization in deoxycholic acid clathrate 2009RaPC...78..244C
    Short-lived radioactivity in the early solar system: The Super-AGB star hypothesis 2012M&PS..tmp..207L
    High-resolution Optical Spectroscopy of DY Cen: Diffuse Interstellar Bands in a Proto-fullerene Circumstellar Environment? 2012ApJ...759L..21G
    The Hot R Coronae Borealis Star DY Centauri is a Binary 2012ApJ...760L...3K
    Infrared Study of Fullerene Planetary Nebulae 2012ApJ...760..107G
    The mixed chemistry phenomenon in Galactic Bulge PNe 2009A&A...495L...5P
    Rubidium, zirconium, and lithium production in intermediate-mass asymptotic giant branch stars 2012A&A...540A..44V
    Oxygen Isotopic Ratios in Cool R Coronae Borealis Stars 2010ApJ...714..144G
    Outburst activity in comets - II. A multiband photometric monitoring of comet 29P/Schwassmann-Wachmann 1 2010MNRAS.409.1682T
    New groups of planetary nebulae with peculiar dust chemistry towards the Galactic bulge 2010A&A...516A..39G
    Heavy Element Nucleosynthesis in the Brightest Galactic Asymptotic Giant Branch Stars 2012ApJ...751....8K
    Evolution of tidal disruption candidates discovered by XMM-Newton 2008A&A...489..543E
    CNO Abundances of Hydrogen-Deficient Carbon and R Coronae Borealis Stars: A View of the Nucleosynthesis in a White Dwarf Merger 2009ApJ...696.1733G
    Are C60 Molecules Detectable in Circumstellar Shells of R Coronae Borealis Stars? 2011ApJ...729..126G
    A search for diffuse bands in the circumstellar envelopes of post-AGB stars 2008A&A...480..133L
    The role of massive AGB stars in the early solar system composition 2009M&PS...44..627T
    The Nature of Dust in Compact Galactic Planetary Nebulae from Spitzer Spectra 2012ApJ...753..172S

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