Chemical Abundances in Stars

Start year
2010
Organizational Unit

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    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 GALAH Survey: non-LTE departure coefficients for large spectroscopic surveys 2020A&A...642A..62A
    A precise architecture characterization of the π Mensae planetary system★ 2020A&A...642A..31D
    HORuS transmission spectroscopy of 55 Cnc e 2020MNRAS.498.4222T
    Geometry of the Draco C1 Symbiotic Binary 2020ApJ...900L..43L
    Characterization of the K2-38 planetary system. Unraveling one of the densest planets known to date 2020A&A...641A..92T
    APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South 2020AJ....160..120J
    The Pristine Inner Galaxy Survey (PIGS) II: Uncovering the most metal-poor populations in the inner Milky Way 2020MNRAS.496.4964A
    Strong chemical tagging with APOGEE: 21 candidate star clusters that have dissolved across the Milky Way disc 2020MNRAS.496.5101P
    Revisiting Proxima with ESPRESSO 2020A&A...639A..77S
    Helium Enhancement in the Metal-rich Red Giants of ω Centauri 2020ApJ...897...32H
    The 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra 2020ApJS..249....3A
    The Stellar Velocity Distribution Function in the Milky Way Galaxy 2020AJ....160...43A
    The Pristine survey - X. A large population of low-metallicity stars permeates the Galactic disc 2020MNRAS.497L...7S
    The Lazy Giants: APOGEE Abundances Reveal Low Star Formation Efficiencies in the Magellanic Clouds 2020ApJ...895...88N
    NLTE for APOGEE: simultaneous multi-element NLTE radiative transfer 2020A&A...637A..80O
    Nightside condensation of iron in an ultrahot giant exoplanet 2020Natur.580..597E
    The Open Cluster Chemical Abundances and Mapping Survey. IV. Abundances for 128 Open Clusters Using SDSS/APOGEE DR16 2020AJ....159..199D
    The Extreme CNO-enhanced Composition of the Primitive Iron-poor Dwarf Star J0815+4729 2020ApJ...889L..13G
    Stellar Characterization of M Dwarfs from the APOGEE Survey: A Calibrator Sample for M-dwarf Metallicities 2020ApJ...890..133S
    Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra 2020MNRAS.492.5470M
    Signatures of the Galactic bar in high-order moments of proper motions measured by Gaia 2020A&A...634A..90P
    The Pristine Survey - VIII. The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime 2020MNRAS.492.4986Y
    Metallicity and α-Element Abundance Gradients along the Sagittarius Stream as Seen by APOGEE 2020ApJ...889...63H
    A detailed non-LTE analysis of LB-1: Revised parameters and surface abundances 2020A&A...634L...7S
    ESPRESSO highlights the binary nature of the ultra-metal-poor giant HE 0107-5240 2020A&A...633A.129B
    Physical parameters of red supergiants in dwarf irregular galaxies in the Local Group 2019A&A...631A..95B
    Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code - II. The Southern clusters and overview 2020MNRAS.492.1641M
    The Pristine survey - VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates 2019MNRAS.490.2241A
    IMF radial gradients in most massive early-type galaxies 2019MNRAS.489.4090L
    Machine learning in APOGEE. Identification of stellar populations through chemical abundances 2019A&A...629A..34G
    The Gaia-ESO survey: Calibrating a relationship between age and the [C/N] abundance ratio with open clusters 2019A&A...629A..62C
    H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia 2019A&A...627A.178F
    ExoMol molecular line lists - XXXIII. The spectrum of Titanium Oxide 2019MNRAS.488.2836M
    Stellar spectral models compared with empirical data 2019MNRAS.486.1814K
    Chemical analysis of CH stars - III. Atmospheric parameters and elemental abundances 2019MNRAS.486.3266P
    High-resolution spectroscopy of Boyajian's star during optical dimming events 2019MNRAS.486..236M
    Back to the Lithium Plateau with the [Fe/H] < -6 Star J0023+0307 2019ApJ...874L..21A
    Exploring circumstellar effects on the lithium and calcium abundances in massive Galactic O-rich AGB stars 2019A&A...623A.151P
    Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. II. Atomic Diffusion in M67 Stars 2019ApJ...874...97S
    Chemical Cartography with APOGEE: Multi-element Abundance Ratios 2019ApJ...874..102W

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