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

    • The Open Cluster Chemical Abundances and Mapping Survey. IV. Abundances for 128 Open Clusters Using SDSS/APOGEE DR16
      The Open Cluster Chemical Abundances and Mapping (OCCAM) survey aims to constrain key Galactic dynamical and chemical evolution parameters by the construction of a large, comprehensive, uniform, infrared-based spectroscopic data set of hundreds of open clusters. This fourth contribution from the OCCAM survey presents analysis using Sloan Digital
      Donor, John et al.

      Advertised on:

      5
      2020
      Citations
      111
    • The Extreme CNO-enhanced Composition of the Primitive Iron-poor Dwarf Star J0815+4729
      We present an analysis of high-resolution Keck/HIRES spectroscopic observations of J0815+4729, an extremely carbon-enhanced, iron-poor dwarf star. These high-quality data allow us to derive a metallicity of [Fe/H] = −5.49 ± 0.14 from the three strongest Fe i lines and to measure a high [Ca/Fe] = 0.75 ± 0.14. The large carbon abundance of A(C) = 7
      González Hernández, Jonay I. et al.

      Advertised on:

      1
      2020
      Citations
      15
    • 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
      2020
      Citations
      34
    • 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.

      Advertised on:

      3
      2020
      Citations
      17
    • 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
      Palicio, Pedro A. et al.

      Advertised on:

      2
      2020
      Citations
      2
    • 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.

      Advertised on:

      3
      2020
      Citations
      53
    • 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.

      Advertised on:

      1
      2020
      Citations
      58
    • 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
      Simón-Díaz, S. et al.

      Advertised on:

      2
      2020
      Citations
      30
    • 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.

      Advertised on:

      1
      2020
      Citations
      6
    • 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.

      Advertised on:

      11
      2019
      Citations
      9
    • Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code - II. The Southern clusters and overview
      We investigate the Fe, C, N, O, Mg, Al, Si, K, Ca, Ce, and Nd abundances of 2283 red giant stars in 31 globular clusters from high-resolution spectra observed in both the northern and Southern hemisphere by the SDSS-IV APOGEE-2 survey. This unprecedented homogeneous data set, largest to date, allows us to discuss the intrinsic Fe spread, the shape
      Mészáros, Szabolcs et al.

      Advertised on:

      2
      2020
      Citations
      111
    • The Pristine survey - VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates
      We present the results of a 3-yr long, medium-resolution spectroscopic campaign aimed at identifying very metal-poor stars from candidates selected with the CaHK, metallicity-sensitive Pristine survey. The catalogue consists of a total of 1007 stars, and includes 146 rediscoveries of metal-poor stars already presented in previous surveys, 707 new
      Aguado, David S. et al.

      Advertised on:

      12
      2019
      Citations
      65
    • IMF radial gradients in most massive early-type galaxies
      Using new long-slit spectroscopy obtained with X-Shooter at ESO-VLT, we study, for the first time, radial gradients of optical and near-infrared initial mass function (IMF)-sensitive features in a representative sample of galaxies at the very high mass end of the galaxy population. The sample consists of seven early-type galaxies (ETGs) at z ̃ 0.05
      La Barbera, F. et al.

      Advertised on:

      11
      2019
      Citations
      48
    • Machine learning in APOGEE. Identification of stellar populations through chemical abundances
      Context. The vast volume of data generated by modern astronomical surveys offers test beds for the application of machine-learning. In these exploratory applications, it is important to evaluate potential existing tools and determine those that are optimal for extracting scientific knowledge from the available observations. Aims: We explore the
      Garcia-Dias, Rafael et al.

      Advertised on:

      9
      2019
      Citations
      12
    • 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
      Casali, G. et al.

      Advertised on:

      9
      2019
      Citations
      52
    • H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia
      We present an elemental abundance analysis of high-resolution spectra for five giant stars spatially located within the innermost regions of the bulge globular cluster NGC 6522 and derive Fe, Mg, Al, C, N, O, Si, and Ce abundances based on H-band spectra taken with the multi-object APOGEE-north spectrograph from the SDSS-IV Apache Point Observatory
      Fernández-Trincado, J. G. et al.

      Advertised on:

      7
      2019
      Citations
      38
    • ExoMol molecular line lists - XXXIII. The spectrum of Titanium Oxide
      Accurate line lists are crucial for correctly modelling a variety of astrophysical phenomena, including stellar photospheres and the atmospheres of extrasolar planets. This paper presents a new line database TOTO for the main isotopologues of titanium oxide (TiO): ^{46}Ti^{16}O, ^{47}Ti^{16}O, ^{48}Ti^{16}O, ^{49}Ti^{16}O, and ^{50}Ti^{16}O. The ^
      McKemmish, Laura K. et al.

      Advertised on:

      9
      2019
      Citations
      169
    • 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
      Knowles, A. T. et al.

      Advertised on:

      6
      2019
      Citations
      8
    • Chemical analysis of CH stars - III. Atmospheric parameters and elemental abundances
      Elemental abundances of CH stars can provide observational constraints for theoretical studies on the nucleosynthesis and evolution of low- and intermediate-mass stars. However, available abundance data in literature are quite scanty. In our pursuit to generate a homogeneous data base of elemental abundances of CH stars we have performed a detailed
      Purandardas, M. et al.

      Advertised on:

      7
      2019
      Citations
      21
    • High-resolution spectroscopy of Boyajian's star during optical dimming events
      Boyajian's star is an apparently normal main-sequence F-type star with a very unusual light curve. The dipping activity of the star, discovered during the Kepler mission, presents deep, asymmetric, and aperiodic events. Here we present high-resolution spectroscopic follow-up during some dimming events recorded post-Kepler observations, from ground
      Martínez González, M. J. et al.

      Advertised on:

      6
      2019
      Citations
      3

    Related talks

    No related talks were found.

    Related conferences

    No related conferences were found.
    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
    Rafael
    Rebolo López