Chemical Abundances in Stars

Start year
2010
Organizational Unit

Related grants:

    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 Pristine survey: XXIII. Data Release 1 and an all-sky metallicity catalogue based on Gaia DR3 BP/RP spectro-photometry
      We used the spectro-photometric information of ∼219 million stars from Gaia's Data Release 3 (DR3) to calculate synthetic, narrowband, metallicity-sensitive CaHK magnitudes that mimic the observations of the Pristine survey, a survey of photometric metallicities of Milky Way stars that has been mapping more than 6500 deg 2 of the northern sky with
      Martin, Nicolas F. et al.

      Advertised on:

      12
      2024
      Citations
      34
    • Multiple reference star differential imaging with VLT/SPHERE: Influence of the reference frame selection and library
      Context. High-contrast imaging observations mostly rely on angular differential imaging, a successful technique for detecting point-sources, such as planets. However, in the vicinity of the star (typically below 300 mas), this technique suffers from signal self-subtraction when there is not enough field rotation. Building large libraries of
      Romero, C. et al.

      Advertised on:

      11
      2024
      Citations
      0
    • The curious case of 2MASS J15594729+4403595, an ultra-fast M2 dwarf with possible Rieger cycles
      Context. RACE-OC (Rotation and ACtivity Evolution in Open Clusters) is a project aimed at characterising the rotational and magnetic activity properties of the late-type members of open clusters, stellar associations, and moving groups of different ages. The evolution in time of rotation and activity at different masses sheds light on the evolution
      Messina, S. et al.

      Advertised on:

      11
      2024
      Citations
      0
    • Magnetic Fields in a Sample of Planet-hosting M Dwarf Stars from Kepler, K2, and TESS Observed by APOGEE
      Stellar magnetic fields have a major impact on space weather around exoplanets orbiting low-mass stars. From an analysis of Zeeman-broadened Fe I lines measured in near-infrared SDSS/APOGEE spectra, mean magnetic fields are determined for a sample of 29 M dwarf stars that host closely orbiting small exoplanets. The calculations employed the
      Wanderley, Fábio et al.

      Advertised on:

      11
      2024
      Citations
      0
    • Correction to: sMILES SSPs: a library of semi-empirical MILES stellar population models with variable [α/Fe] abundances
      Knowles, Adam T. et al.

      Advertised on:

      11
      2024
      Citations
      0
    • Two black widow pulsars in the optical and X-rays
      Context. Two millisecond pulsars, PSR J1513‑2550 and PSR J2017‑1614, with spin periods of about 2.1 and 2.3 ms were recently discovered in the radio and γ-rays and classified as black widow pulsars in tight binary stellar systems with orbital periods of about 4.3 and 2.3 h. Aims. Our goals are to reveal the fundamental parameters of both systems
      Bobakov, A. V. et al.

      Advertised on:

      10
      2024
      Citations
      1
    • The R-process Alliance: Fifth Data Release from the Search for R-process-enhanced Metal-poor Stars in the Galactic Halo with the GTC
      Understanding the abundance pattern of metal-poor stars and the production of heavy elements through various nucleosynthesis processes offers crucial insights into the chemical evolution of the Milky Way, revealing primary sites and major sources of rapid neutron-capture process (r-process) material in the Universe. In this fifth data release from
      Bandyopadhyay, Avrajit et al.

      Advertised on:

      10
      2024
      Citations
      3
    • A sub-Earth-mass planet orbiting Barnard's star
      Context. ESPRESSO guaranteed time observations (GTOs) at the 8.2m VLT telescope were performed to look for Earth-like exoplanets in the habitable zone of nearby stars. Barnard's star is a primary target within the ESPRESSO GTO as it is the second closest neighbour to our Sun after the α Centauri stellar system. Aims. We present here a large set of
      González Hernández, J. I. et al.

      Advertised on:

      10
      2024
      Citations
      5
    • The Gaia ultracool dwarf sample-IV. GTC/OSIRIS optical spectra of Gaia late-M and L dwarfs
      As part of our comprehensive, ongoing characterization of the low-mass end of the main sequence in the Solar neighbourhood, we used the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias to acquire low- and mid-resolution (R ${\approx }$300 and R ${\approx }$2500) optical spectroscopy of 53 late-M and L ultracool dwarfs. Most of these objects
      Cooper, W. J. et al.

      Advertised on:

      10
      2024
      Citations
      0
    • The Pristine Inner Galaxy Survey (PIGS): IX. The largest detailed chemical analysis of very metal-poor stars in the Sagittarius dwarf galaxy
      The most metal-poor stars provide valuable insights into the early chemical enrichment history of a system, carrying the chemical imprints of the first generations of supernovae. The most metal-poor region of the Sagittarius dwarf galaxy remains inadequately observed and characterised. To date, only ∼4 stars with [Fe/H] < ‑2.0 have been chemically
      Sestito, Federico et al.

      Advertised on:

      9
      2024
      Citations
      8
    • Isotopic abundance of carbon in the DLA towards QSO B1331+170
      Chemical evolution models predict a gradual build-up of 13C in the Universe, based on empirical nuclear reaction rates and assumptions on the properties of stellar populations. However, old metal-poor stars within the Galaxy contain more 13C than is predicted, suggesting that further refinements to the models are necessary. Gas at high-redshift
      Milaković, Dinko et al.

      Advertised on:

      10
      2024
      Citations
      1
    • ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b
      Context. Ultra hot Jupiters (gas giants with T eq > 2000 K) are intriguing exoplanets due to the extreme physics and chemistry present in their atmospheres. Their torrid daysides can be characterised using ground-based high-resolution emission spectroscopy. Aims. We search for signatures of neutral and singly ionised iron (Fe I and Fe II
      Costa Silva, A. R. et al.

      Advertised on:

      9
      2024
      Citations
      0
    • Three super-Earths and a possible water world from TESS and ESPRESSO
      Context. Since 2018, the ESPRESSO spectrograph at the VLT has been hunting for planets in the southern skies via the radial velocity (RV) method. One of its goals is to follow up on candidate planets from transit surveys such as the TESS mission, with a particular focus on small planets for which ESPRESSO's RV precision is vital. Aims: We aim to
      Hobson, M. J. et al.

      Advertised on:

      8
      2024
      Citations
      2
    • The updated BOSZ synthetic stellar spectral library
      Context. The modeling of stellar spectra of flux standards observed by the Hubble and James Webb space telescopes requires a large synthetic spectral library that covers a wide atmospheric parameter range. Aims: The aim of this paper is to present and describe the calculation methods behind the updated version of the BOSZ synthetic spectral
      Mészáros, Szabolcs et al.

      Advertised on:

      8
      2024
      Citations
      1
    • Magnetic Fields in M-dwarf Members of the Pleiades Open Cluster Using APOGEE Spectra
      Average magnetic field measurements are presented for 62 M-dwarf members of the Pleiades open cluster, derived from Zeeman-enhanced Fe I lines in the H band. A Markov Chain Monte Carlo methodology was employed to model magnetic filling factors using Sloan Digital Sky Survey (SDSS) IV APOGEE high-resolution spectra, along with the radiative transfer
      Wanderley, Fábio et al.

      Advertised on:

      8
      2024
      Citations
      3
    • DESI Early Data Release Milky Way Survey value-added catalogue
      We present the stellar value-added catalogue based on the Dark Energy Spectroscopic Instrument (DESI) Early Data Release. The catalogue contains radial velocity and stellar parameter measurements for $\simeq$ 400 000 unique stars observed during commissioning and survey validation by DESI. These observations were made under conditions similar to
      Koposov, Sergey E. et al.

      Advertised on:

      9
      2024
      Citations
      7
    • Discovery of an Extremely r-process-enhanced Thin-disk Star with [Eu/H] = +0.78
      Highly r-process-enhanced (RPE) stars are rare and usually metal poor ([Fe/H] < ‑1.0), and they mainly populate the Milky Way halo and dwarf galaxies. This study presents the discovery of a relatively bright (V = 12.72), highly RPE (r-II) star ([Eu/Fe] = +1.32, [Ba/Eu] = ‑0.95), LAMOST J020623.21+494127.9. This star was selected from the Large Sky
      Xie, Xiao-Jin et al.

      Advertised on:

      8
      2024
      Citations
      1
    • Single-epoch and Differential Astrometric Microlensing of Quasars
      We propose and discuss a new experimental approach to measure the centroid shift induced by gravitational microlensing in the images of lensed quasars (astrometric microlensing). Our strategy is based on taking the photocenter of a region in the quasar large enough as to be insensitive to microlensing as reference to measure the centroid
      Forés-Toribio, R. et al.

      Advertised on:

      7
      2024
      Citations
      0
    • The Early Data Release of the Dark Energy Spectroscopic Instrument
      The Dark Energy Spectroscopic Instrument (DESI) completed its 5 month Survey Validation in 2021 May. Spectra of stellar and extragalactic targets from Survey Validation constitute the first major data sample from the DESI survey. This paper describes the public release of those spectra, the catalogs of derived properties, and the intermediate data
      DESI Collaboration et al.

      Advertised on:

      8
      2024
      Citations
      235
    • AuriDESI: mock catalogues for the DESI Milky Way Survey
      The Dark Energy Spectroscopic Instrument Milky Way Survey (DESI MWS) will explore the assembly history of the Milky Way by characterizing remnants of ancient dwarf galaxy accretion events and improving constraints on the distribution of dark matter in the outer halo. We present mock catalogues that reproduce the selection criteria of MWS and the
      Kizhuprakkat, Namitha et al.

      Advertised on:

      7
      2024
      Citations
      1

    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