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

    • Gaia-ESO survey: Lithium abundances in open cluster Red Clump stars

      Context. It has recently been suggested that all giant stars with masses below 2 M⊙ suffer an episode of surface lithium enrichment between the tip of the red giant branch (RGB) and the red clump (RC). Aims: We test if the above result can be confirmed in a sample of RC and RGB stars that are members of open clusters. Methods: We discuss Li

      Magrini, L. et al.

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      11
      2021
      Citations
      18
    • CAPOS: The bulge Cluster APOgee Survey. I. Overview and initial ASPCAP results

      Context. Bulge globular clusters (BGCs) are exceptional tracers of the formation and chemodynamical evolution of this oldest Galactic component. However, until now, observational difficulties have prevented us from taking full advantage of these powerful Galactic archeological tools. Aims: CAPOS, the bulge Cluster APOgee Survey, addresses this key

      Geisler, D. et al.

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      8
      2021
      Citations
      18
    • Double-lined Spectroscopic Binaries in the APOGEE DR16 and DR17 Data

      APOGEE spectra offer ≲1 km s-1 precision in the measurement of stellar radial velocities. This holds even when multiple stars are captured in the same spectrum, as happens most commonly with double-lined spectroscopic binaries (SB2s), although random line-of-sight alignments of unrelated stars can also occur. We develop a code that autonomously

      Kounkel, Marina et al.

      Advertised on:

      11
      2021
      Citations
      44
    • Symbiotic Stars in the Apache Point Observatory Galactic Evolution Experiment Survey: The Case of LIN 358 and SMC N73 (LIN 445a)

      LIN 358 and SMC N73 are two symbiotic binaries in the halo of the Small Magellanic Cloud, each composed of a hot white dwarf accreting from a cool giant companion. In this work, we characterize these systems using a combination of spectral energy distribution (SED)-fitting to the extant photometric data spanning a broad wavelength range (X-ray

      Washington, Jasmin E. et al.

      Advertised on:

      9
      2021
      Citations
      3
    • Alternative Strategies to Solve the Stellar Atmosphere Problem

      At the heart of the computation of model atmospheres there is the so-called Stellar Atmosphere Problem, which consists of the self-consistent solution of the radiative transfer equations under specific constraints. The amazing progresses achieved in the field since the 1970s are due to both the dramatic increase of the computational facilities and

      Crivellari, L.

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      6
      2021
      Citations
      0
    • Testing the Limits of Precise Subgiant Characterization with APOGEE and Gaia: Opening a Window to Unprecedented Astrophysical Studies

      Given their location on the Hertzsprung-Russell (H-R) diagram, thoroughly characterized subgiant stars can place stringent constraints on a wide range of astrophysical problems. Accordingly, they are prime asteroseismic targets for the Transiting Exoplanet Survey Satellite (TESS) mission. In this work, we infer stellar properties for a sample of

      Godoy-Rivera, Diego et al.

      Advertised on:

      7
      2021
      Citations
      12
    • Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code ‑ III. ω Cen

      We study the multiple populations of ω Cen by using the abundances of Fe, C, N, O, Mg, Al, Si, K, Ca, and Ce from the high-resolution, high signal-to-noise (S/N>70) spectra of 982 red giant stars observed by the SDSS-IV/APOGEE-2 survey. We find that the shape of the Al-Mg and N-C anticorrelations changes as a function of metallicity, continuous for

      Mészáros, Szabolcs et al.

      Advertised on:

      8
      2021
      Citations
      14
    • Chemodynamically Characterizing the Jhelum Stellar Stream with APOGEE-2

      We present the kinematic and chemical profiles of red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE)-2 survey in the direction of the Jhelum stellar stream, a Milky Way substructure located in the inner halo of the Milky Way at a distance from the Sun of ≍13 kpc. From the six APOGEE-2 Jhelum pointings

      Sheffield, Allyson A. et al.

      Advertised on:

      5
      2021
      Citations
      3
    • APOGEE view of the globular cluster NGC 6544

      The second phase of the APOGEE survey is providing near-infrared (near-IR), high-resolution, high signal-to-noise spectra of stars in the halo, disc, bar, and bulge of the Milky Way. The near-IR spectral window is especially important in the study of the Galactic bulge, where stars are obscured by the dust and gas of the disc in its line of sight

      Gran, F. et al.

      Advertised on:

      7
      2021
      Citations
      6
    • An enquiry on the origins of N-rich stars in the inner Galaxy based on APOGEE chemical compositions

      Recent evidence based on APOGEE data for stars within a few kpc of the Galactic Centre suggests that dissolved globular clusters (GCs) contribute significantly to the stellar mass budget of the inner halo. In this paper, we enquire into the origins of tracers of GC dissolution, N-rich stars, that are located in the inner 4 kpc of the Milky Way

      Kisku, Shobhit et al.

      Advertised on:

      6
      2021
      Citations
      11
    • The APOGEE Data Release 16 Spectral Line List

      The updated H-band spectral-line list (from λ15000-17000) adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) for the SDSS-IV Data Release 16 (DR16) is presented in this work. The APOGEE line list is a combination of atomic and molecular lines, with data drawn from laboratory, theoretical, and astrophysical sources

      Smith, Verne V. et al.

      Advertised on:

      6
      2021
      Citations
      73
    • Orbital Torus Imaging: Using Element Abundances to Map Orbits and Mass in the Milky Way

      Many approaches to galaxy dynamics assume that the gravitational potential is simple and the distribution function is time invariant. Under these assumptions there are traditional tools for inferring potential parameters given observations of stellar kinematics (e.g., Jeans models). However, spectroscopic surveys measure many stellar properties

      Price-Whelan, Adrian M. et al.

      Advertised on:

      3
      2021
      Citations
      12
    • Carbon dust in the evolved born-again planetary nebulae A 30 and A 78

      We present an infrared (IR) characterization of the born-again planetary nebulae (PNe) A 30 and A 78 using IR images and spectra. We demonstrate that the carbon-rich dust in A 30 and A 78 is spatially coincident with the H-poor ejecta and coexists with hot X-ray-emitting gas up to distances of 50 arcsec from the central stars of PNe (CSPNe). Dust

      Toalá, J. A. et al.

      Advertised on:

      5
      2021
      Citations
      12
    • Understanding the evolution and dust formation of carbon stars in the Large Magellanic Cloud via the JWST

      Context. Carbon stars have been, and still are, extensively studied. Given their complex internal structure and their peculiar chemical composition, they are living laboratories in which we can test stellar structure and evolution theories of evolved stars. Furthermore, they are the most relevant dust manufacturers, thus playing a crucial role in

      Marini, E. et al.

      Advertised on:

      3
      2021
      Citations
      9
    • The Similarity of Abundance Ratio Trends and Nucleosynthetic Patterns in the Milky Way Disk and Bulge

      We compare abundance ratio trends in a sample of ∼11,000 Milky Way bulge stars (RGC < 3 kpc) from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to those of APOGEE stars in the Galactic disk (5 kpc < RGC < 11 kpc). We divide each sample into low-Ia (high-[Mg/Fe]) and high-Ia (low-[Mg/Fe]) populations, and in each population, we

      Griffith, Emily et al.

      Advertised on:

      3
      2021
      Citations
      38
    • The APOGEE Library of Infrared SSP Templates (A-LIST): High-resolution Simple Stellar Population Spectral Models in the H Band

      Integrated light spectroscopy from galaxies can be used to study the stellar populations that cannot be resolved into individual stars. This analysis relies on stellar population synthesis (SPS) techniques to study the formation history and structure of galaxies. However, the spectral templates available for SPS are limited, especially in the near

      Ashok, Aishwarya et al.

      Advertised on:

      4
      2021
      Citations
      8
    • Probing 3D and NLTE models using APOGEE observations of globular cluster stars

      Context. Hydrodynamical (or 3D) and non-local thermodynamic equilibrium (NLTE) effects are known to affect abundance analyses. However, there are very few observational abundance tests of 3D and NLTE models. Aims: We developed a new way of testing the abundance predictions of 3D and NLTE models, taking advantage of large spectroscopic survey data

      Masseron, T. et al.

      Advertised on:

      3
      2021
      Citations
      5
    • An Intermediate-age Alpha-rich Galactic Population in K2

      We explore the relationships between the chemistry, ages, and locations of stars in the Galaxy using asteroseismic data from the K2 mission and spectroscopic data from the Apache Point Galactic Evolution Experiment survey. Previous studies have used giant stars in the Kepler field to map the relationship between the chemical composition and the

      Warfield, Jack T. et al.

      Advertised on:

      3
      2021
      Citations
      9
    • Atomic data for the Gaia-ESO Survey

      Context. We describe the atomic and molecular data that were used for the abundance analyses of FGK-type stars carried out within the Gaia-ESO Public Spectroscopic Survey in the years 2012 to 2019. The Gaia-ESO Survey is one among several current and future stellar spectroscopic surveys producing abundances for Milky-Way stars on an industrial

      Heiter, U. et al.

      Advertised on:

      1
      2021
      Citations
      83
    • Are extreme asymptotic giant branch stars post-common envelope binaries?

      Modelling dust formation in single stars evolving through the carbon-star stage of the asymptotic giant branch (AGB) reproduces well the mid-infrared colours and magnitudes of most of the C-rich sources in the Large Magellanic Cloud (LMC), apart from a small subset of extremely red objects (EROs). An analysis of the spectral energy distributions of

      Dell'Agli, F. et al.

      Advertised on:

      2
      2021
      Citations
      6

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