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

    • Low-mass low-metallicity AGB stars as an efficient i-process site explaining CEMP-rs stars

      Context. Among carbon-enhanced metal-poor (CEMP) stars, some are found to be enriched in slow-neutron capture (s-process) elements (and are then tagged CEMP-s), some have overabundances in rapid-neutron capture (r-process) elements (tagged CEMP-r), and some are characterized by both s- and r-process enrichments (tagged CEMP-rs). The current

      Karinkuzhi, D. et al.

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      1
      2021
      Citations
      28
    • The contribution of N-rich stars to the Galactic stellar halo using APOGEE red giants

      The contribution of dissolved globular clusters (GCs) to the stellar content of the Galactic halo is a key constraint on models for GC formation and destruction, and the mass assembly history of the Milky Way. Earlier results from APOGEE pointed to a large contribution of destroyed GCs to the stellar content of the inner halo, by as much as 25 ${{\

      Horta, Danny et al.

      Advertised on:

      1
      2021
      Citations
      31
    • Carbon-enhanced metal-poor stars enriched in s-process and r-process elements

      We present an on-going project consisting of analysis of a sample of twenty-five metal-poor stars, most of them carbon-enriched and thus tagged carbon-enhanced metal-poor (CEMP) stars, observed with the high-resolution HERMES spectrograph mounted on the Mercator telescope (La Palma), the UVES spectrograph on VLT (ESO Chile), or the HIRES

      Karinkuzhi, Drisya et al.

      Advertised on:

      12
      2020
      Citations
      0
    • Exploring the Galactic Warp through Asymmetries in the Kinematics of the Galactic Disk

      Previous analyses of large databases of Milky Way stars have revealed the stellar disk of our Galaxy to be warped and that this imparts a strong signature on the kinematics of stars beyond the solar neighborhood. However, due to the limitation of accurate distance estimates, many attempts to explore the extent of these Galactic features have

      Cheng, Xinlun et al.

      Advertised on:

      12
      2020
      Citations
      28
    • Wide binaries in planetary nebulae with Gaia DR2

      Context. The Gaia Data Release 2 (DR2) was used to select a sample of 211 central stars of planetary nebulae (CSPNe) with good-quality astrometric measurements, which we refer to as Golden Astrometry Planetary Nebulae (GAPN). Gaia astrometric and photometric measurements allowed us to derive accurate distances and radii and to calculate

      González-Santamaría, I. et al.

      Advertised on:

      12
      2020
      Citations
      8
    • Heavy-element Abundances in P-rich Stars: A New Site for the s-process?

      The recently discovered phosphorus-rich stars pose a challenge to stellar evolution and nucleosynthesis theory, as none of the existing models can explain their extremely peculiar chemical abundances pattern. Apart from the large phosphorus enhancement, such stars also show enhancement in other light (O, Mg, Si, and Al) and heavy (e.g., Ce)

      Masseron, T. et al.

      Advertised on:

      11
      2020
      Citations
      10
    • Open Cluster Chemical Homogeneity throughout the Milky Way

      The chemical homogeneity of surviving stellar clusters contains important clues about interstellar medium (ISM) mixing efficiency, star formation, and the enrichment history of the Galaxy. Existing measurements in a handful of open clusters suggest homogeneity in several elements at the 0.03 dex level. Here we present (i) a new cluster member

      Poovelil, Vijith Jacob et al.

      Advertised on:

      11
      2020
      Citations
      16
    • The Gaia-ESO Survey: Calibrating the lithium-age relation with open clusters and associations. I. Cluster age range and initial membership selections

      Context. Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars, these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity

      Gutiérrez Albarrán, M. L. et al.

      Advertised on:

      11
      2020
      Citations
      29
    • How many components? Quantifying the complexity of the metallicity distribution in the Milky Way bulge with APOGEE

      We use data of ∼13-=000 stars from the Sloan Digital Sky Survey/Apache Point Observatory Galactic Evolution Experiment survey to study the shape of the bulge metallicity distribution function (MDF) within the region |ℓ| ≤ 11° and |b| ≤ 13°, and spatially constrained to RGC ≤ 3.5 kpc. We apply Gaussian mixture modelling and non-negative matrix

      Rojas-Arriagada, Alvaro et al.

      Advertised on:

      9
      2020
      Citations
      42
    • The Gaia-ESO Survey: A new diagnostic for accretion and outflow activity in the young cluster NGC 2264

      Context. NGC 2264 is a young cluster whose accretion properties can be investigated in detail by taking advantage of the FLAMES data in the context of the Gaia-ESO Survey. In fact, the analysis of the Hα emission line profile can provide us with information about the accretion and ejection activity of young stars. However, a strong nebular emission

      Bonito, R. et al.

      Advertised on:

      10
      2020
      Citations
      11
    • Cool stars in the Galactic center as seen by APOGEE. M giants, AGB stars, and supergiant stars and candidates

      The Galactic center region, including the nuclear disk, has until recently been largely avoided in chemical census studies because of extreme extinction and stellar crowding. Large, near-IR spectroscopic surveys, such as the Apache Point Observatory Galactic Evolution Experiment (APOGEE), allow the measurement of metallicities in the inner region

      Schultheis, M. et al.

      Advertised on:

      10
      2020
      Citations
      14
    • Exploring the Stellar Age Distribution of the Milky Way Bulge Using APOGEE

      We present stellar age distributions of the Milky Way bulge region using ages for ∼6000 high-luminosity ( $\mathrm{log}(g)\lt 2.0$ ), metal-rich ([Fe/H] ≥ -0.5) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment. Ages are derived using The Cannon label-transfer method, trained on a sample of nearby luminous giants

      Hasselquist, Sten et al.

      Advertised on:

      10
      2020
      Citations
      33
    • Geometry of the Draco C1 Symbiotic Binary

      Draco C1 is a known symbiotic binary star system composed of a carbon red giant and a hot, compact companion—likely a white dwarf—belonging to the Draco dwarf spheroidal galaxy. From near-infrared spectroscopic observations taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), part of Sloan Digital Sky Survey IV, we

      Lewis, Hannah M. et al.

      Advertised on:

      9
      2020
      Citations
      7
    • The Milky Way's bulge star formation history as constrained from its bimodal chemical abundance distribution

      We conduct a quantitative analysis of the star formation history (SFH) of the Milky Way's (MW) bulge by exploiting the constraining power of its stellar [Fe/H] and [Mg/Fe] distribution functions. Using Apache Point Observatory Galactic Evolution Experiment survey data, we confirm the previously established bimodal [Mg/Fe]-[Fe/H] distribution within

      Lian, Jianhui et al.

      Advertised on:

      7
      2020
      Citations
      18
    • Phosphorus-rich stars with unusual abundances are challenging theoretical predictions

      Almost all chemical elements have been made by nucleosynthetic reactions in various kind of stars and have been accumulated along our cosmic history. Among those elements, the origin of phosphorus is of extreme interest because it is known to be essential for life such as we know on Earth. However, current models of (Galactic) chemical evolution

      Masseron, Thomas et al.

      Advertised on:

      8
      2020
      Citations
      16
    • APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South

      The spectral analysis and data products in Data Release 16 (DR16; 2019 December) from the high-resolution near-infrared Apache Point Observatory Galactic Evolution Experiment (APOGEE)-2/Sloan Digital Sky Survey (SDSS)-IV survey are described. Compared to the previous APOGEE data release (DR14; 2017 July), APOGEE DR16 includes about 200,000 new

      Jönsson, Henrik et al.

      Advertised on:

      9
      2020
      Citations
      276
    • The age-chemical abundance structure of the Galactic disc - II. α-dichotomy and thick disc formation

      We extend our previous work on the age-chemical abundance structure of the Galactic outer disc to the inner disc (4 < r < 8 kpc) based on the SDSS/APOGEE survey. Different from the outer disc, the inner disc stars exhibit a clear bimodal distribution in the [Mg/Fe]-[Fe/H] plane. While a number of scenarios have been proposed in the literature, it

      Lian, Jianhui et al.

      Advertised on:

      7
      2020
      Citations
      43
    • Assessing spectra and thermal inversions due to TiO in hot Jupiter atmospheres

      Recent detections of thermal inversions in the dayside atmospheres of some hot Jupiters are motivating new avenues to understand the interplay between their temperature structures and other atmospheric conditions. In particular, TiO has long been proposed to cause thermal inversions in hot Jupiters, depending on other factors such as stellar

      Piette, Anjali A. A. et al.

      Advertised on:

      7
      2020
      Citations
      21
    • Strong chemical tagging with APOGEE: 21 candidate star clusters that have dissolved across the Milky Way disc

      Chemically tagging groups of stars born in the same birth cluster is a major goal of spectroscopic surveys. To investigate the feasibility of such strong chemical tagging, we perform a blind chemical tagging experiment on abundances measured from APOGEE survey spectra. We apply a density-based clustering algorithm to the 8D chemical space defined

      Price-Jones, Natalie et al.

      Advertised on:

      7
      2020
      Citations
      28
    • Physical characterization of 2020 AV<SUB>2</SUB>, the first known asteroid orbiting inside Venus orbit

      The first known asteroid with the orbit inside that of Venus is 2020 AV2. This may be the largest member of a new population of small bodies with the aphelion smaller than 0.718 au, called Vatiras. The surface of 2020 AV2 is being constantly modified by the high temperature, by the strong solar wind irradiation that characterizes the innermost

      Popescu, M. et al.

      Advertised on:

      6
      2020
      Citations
      12

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