Chemical Abundances in Stars

Start year
2010
Organizational Unit

Grants related:

    General
    Description

    Stellar spectroscopy allows us to determine the properties and chemical compositions of stars. From this information for stars of different ages in the Milky Way, it is possible to reconstruct the chemical evolution of the Galaxy, as well as the origin of the elements heavier than boron, created mainly in stellar interiors. It is also possible to study stellar formation, and the formation of the Galaxy, from the signature of the Galactic potential on the stellar orbits, and the distributions of mass, ages, and the abundance of heavy elements.

    Obtaining high-resolution spectra, as necessary for studies of chemical compositions, requires advanced and efficient instrumentation. This is particularly true for research that calls for large stellar samples, which demands the observation of hundreds or thousands of sources simultaneously. Efficiency requires that the data processing and analysis are performed in an automated way.

    The interpretation of spectra is based on physical models of the atmospheres of the stars, from where the light that we observe escapes the stars. The main ingredients for building such models are the fluid dynamics, and the properties of the atoms, ions, and molecules, especially regarding their interactions with the radiation coming from the stellar interior.

    Once we have a plausible model, it is possible to compute in detail how the radiation propagates through the stellar atmosphere, and the emergent spectrum, which can then be iteratively compared with the observations to refine the model.

    This project covers three different research fronts:

    - Improving model atmospheres and simulations of stellar spectra.

    - Developing tools for acquisition, reduction, and analysis of spectroscopic observations, in particular for the determination of chemical abundances in stars.

    - Designing, preparing, and executing spectroscopic studies of stars aimed at understanding a) the most relevant aspects of the physics of stellar atmospheres, b) the formation and evolution of stars, c) the origin of the chemical elements, and d) the formation, structure, and evolution of the Milky Way galaxy.

    Principal investigator
    Project staff
    Collaborators
    Dr.
    I. Hubeny
    Dr.
    B. Castanheira
    Dr.
    M. Kilic
    Dr.
    S. Majewski
    Dr.
    H.G. Ludwig
    Dr.
    M. Cropper
    Dr.
    M. P. Ruffoni
    Dr.
    J. C. Pickering
    Dr.
    K. Cunha
    Dr.
    Andrew Cooper
    Dr.
    Boris Gaensicke
    1. Complete the installation and commissioning of HORuS on GTC
    2. Discover two new stars with more than 100,000 times less iron than the Sun
    3. Complete the classification of all the APOGEE spectra with K-means
    4. Publish a complete collection of model stellar spectra for stars O to M
    5. Identify the signature of chemical diffusion in the atmospheres of the stars in the cluster M67

    Related publications

    • Stellar Characterization of M Dwarfs from the APOGEE Survey: A Calibrator Sample for M-dwarf Metallicities

      We present spectroscopic determinations of the effective temperatures, surface gravities, and metallicities for 21 M dwarfs observed at high resolution (R ∼ 22,500) in the H band as part of the Sloan Digital Sky Survey (SDSS)-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. The atmospheric parameters and metallicities are

      Souto, Diogo et al.

      Advertised on:

      2
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    • Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

      With the purpose of assessing classic spectroscopic methods on high-resolution and high signal-to-noise ratio spectra in the near-infrared wavelength region, we selected a sample of 65 F-, G-, and K-type stars observed with CARMENES, the new, ultra-stable, double-channel spectrograph at the 3.5 m Calar Alto telescope. We computed their stellar

      Marfil, E. et al.

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    • Signatures of the Galactic bar in high-order moments of proper motions measured by Gaia

      Our location in the Milky Way provides an exceptional opportunity to gain insight on the galactic evolution processes, and complement the information inferred from observations of external galaxies. Since the Milky Way is a barred galaxy, the study of motions of individual stars in the bulge and disc is useful to understand the role of the bar. The

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    • The Pristine Survey - VIII. The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime

      The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ( [Fe/H] < -3), and currently consists of over 4 million FGK-type stars over a sky area of ̃ 2500 deg^2. We focus our analysis on a subsample of ̃80 000 main-sequence turn-off stars with heliocentric distances between 6 and 20 kpc

      Youakim, K. et al.

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    • Metallicity and α-Element Abundance Gradients along the Sagittarius Stream as Seen by APOGEE

      Using 3D positions and kinematics of stars relative to the Sagittarius (Sgr) orbital plane and angular momentum, we identify 166 Sgr stream members observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) that also have Gaia DR2 astrometry. This sample of 63/103 stars in the Sgr trailing/leading arm is combined with an APOGEE

      Hayes, Christian R. et al.

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    • A detailed non-LTE analysis of LB-1: Revised parameters and surface abundances

      Context. It has recently been proposed that LB-1 is a binary system at 4 kpc consisting of a B-type star of 8 M☉ and a massive stellar black hole (BH) of 70 M☉. This finding challenges our current theories of massive star evolution and formation of BHs at solar metallicity. Aims: Our objective is to derive the effective temperature, surface gravity

      Simón-Díaz, S. et al.

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    • ESPRESSO highlights the binary nature of the ultra-metal-poor giant HE 0107-5240

      Context. The vast majority of the known stars of ultra low metallicity ([Fe/H] < -4.5) are known to be enhanced in carbon, and belong to the "low-carbon band" (A(C) = log(C/H)+12 ≤ 7.6). It is generally, although not universally, accepted that this peculiar chemical composition reflects the chemical composition of the gas cloud out of which these

      Bonifacio, P. et al.

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    • Physical parameters of red supergiants in dwarf irregular galaxies in the Local Group

      Context. Increasing the statistics of evolved massive stars in the Local Group enables investigating their evolution at different metallicities. During the late stages of stellar evolution, the physics of some phenomena, such as episodic and systematic mass loss, are not well constrained. For example, the physical properties of red supergiants

      Britavskiy, N. E. et al.

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    • Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code - II. The Southern clusters and overview

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      Mészáros, Szabolcs et al.

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    • The Pristine survey - VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates

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      Aguado, David S. et al.

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    • IMF radial gradients in most massive early-type galaxies

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    • Machine learning in APOGEE. Identification of stellar populations through chemical abundances

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      Garcia-Dias, Rafael et al.

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    • The Gaia-ESO survey: Calibrating a relationship between age and the [C/N] abundance ratio with open clusters

      Context. In the era of large high-resolution spectroscopic surveys such as Gaia-ESO and APOGEE, high-quality spectra can contribute to our understanding of the Galactic chemical evolution by providing abundances of elements that belong to the different nucleosynthesis channels, and also by providing constraints to one of the most elusive

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    • H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia

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    • ExoMol molecular line lists - XXXIII. The spectrum of Titanium Oxide

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    • Stellar spectral models compared with empirical data

      The empirical MILES stellar library is used to test the accuracy of three different, state-of-the-art, theoretical model libraries of stellar spectra. These models are widely used in the literature for stellar population analysis. A differential approach is used so that responses to elemental abundance changes are tested rather than absolute levels

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    • Chemical analysis of CH stars - III. Atmospheric parameters and elemental abundances

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    • High-resolution spectroscopy of Boyajian's star during optical dimming events

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    • Back to the Lithium Plateau with the [Fe/H] < -6 Star J0023+0307

      We present an analysis of the Ultraviolet and Visual Echelle Spectrograph (UVES) high-resolution spectroscopic observations at the 8.2 m Very Large Telescope of J0023+0307, a main-sequence extremely iron-poor dwarf star. We are unable to detect iron lines in the spectrum but derive [Fe/H] < -6.1 from the Ca II resonance lines assuming [Ca/Fe] ≥ 0

      Aguado, D. S. et al.

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    • Exploring circumstellar effects on the lithium and calcium abundances in massive Galactic O-rich AGB stars

      Context. We previously explored the circumstellar effects on Rb and Zr abundances in a sample (21) of massive Galactic O-rich asymptotic giant branch (AGB) stars. Here we are interested in clarifying the role of the extended atmosphere in the case of Li and Ca. Li is an important indicator of hot bottom burning while the total Ca abundances in

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    Related talks

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    Related conferences

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    Related projects
    Optical bench
    HORuS - High Optical Resolution Spectrograph

    High-resolution spectrograph for the 10-m Gran Telescopio Canarias (GTC) based on components from UES, a spectrograph which was in use at the 4.2-m William Herschel Telescope (WHT) between 1992 and 2001.

    Carlos
    Allende Prieto
    Gran Telescopio Canarias (GTC)
    SEVERO OCHOA 2016 - 2019

    The IAC is an internationalized Spanish research centre aiming to achieve major advances in the understanding of the laws that govern the origin and evolution of the various forms of matter/energy in the Universe. Outstanding results are expected in key areas of research such as Solar physics, Sun-Earth connections, Exoplanetary systems, Solar

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