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

    Ca line formation in late-type stellar atmospheres. I. The model atom 2019A&A...623A.103O
    J-PLUS: The Javalambre Photometric Local Universe Survey 2019A&A...622A.176C
    J-PLUS: Identification of low-metallicity stars with artificial neural networks using SPHINX 2019A&A...622A.182W
    Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The northern clusters 2019A&A...622A.191M
    Gaia Data Release 2. Properties and validation of the radial velocities 2019A&A...622A.205K
    Identifying Sagittarius Stream Stars by Their APOGEE Chemical Abundance Signatures 2019ApJ...872...58H
    Constraining Metallicity-dependent Mixing and Extra Mixing Using [C/N] in Alpha-rich Field Giants 2019ApJ...872..137S
    The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA-derived Quantities, Data Visualization Tools, and Stellar Library 2019ApJS..240...23A
    The Gaia-ESO Survey: impact of extra mixing on C and N abundances of giant stars 2019A&A...621A..24L
    Radial Velocities in the Outermost Disk toward the Anticenter 2019AJ....157...26L
    The origin of accreted stellar halo populations in the Milky Way using APOGEE, Gaia, and the EAGLE simulations 2019MNRAS.482.3426M
    Comprehensive comparison between APOGEE and LAMOST. Radial velocities and atmospheric stellar parameters 2018A&A...620A..76A
    A collection of model stellar spectra for spectral types B to early-M 2018A&A...618A..25A
    The Origin of the 300 km s‑1 Stream near Segue 1 2018ApJ...866...42F
    The Pristine survey IV: approaching the Galactic metallicity floor with the discovery of an ultra-metal-poor star 2018MNRAS.481.3838S
    The Gaia-ESO Survey: the origin and evolution of s-process elements 2018A&A...617A.106M
    The Gaia-ESO Survey: properties of newly discovered Li-rich giants 2018A&A...617A...4S
    Gaia Data Release 2. Gaia Radial Velocity Spectrometer 2018A&A...616A...5C
    Gaia Data Release 2. Processing the spectroscopic data 2018A&A...616A...6S
    Gaia Data Release 2. Calibration and mitigation of electronic offset effects in the data 2018A&A...616A..15H
    A Chemical and Kinematical Analysis of the Intermediate-age Open Cluster IC 166 from APOGEE and Gaia DR2 2018AJ....156...94S
    APOGEE Data Releases 13 and 14: Data and Analysis 2018AJ....156..125H
    APOGEE Data Releases 13 and 14: Stellar Parameter and Abundance Comparisons with Independent Analyses 2018AJ....156..126J
    Testing models of stellar structure and evolution - I. Comparison with detached eclipsing binaries 2018MNRAS.479.1953D
    Stellar and Planetary Characterization of the Ross 128 Exoplanetary System from APOGEE Spectra 2018ApJ...860L..15S
    Signatures of the Galactic bar on stellar kinematics unveiled by APOGEE 2018MNRAS.478.1231P
    Chemical Composition of Two Bright, Extremely Metal-poor Stars from the SDSS MARVELS Pre-survey 2018ApJ...859..114B
    Machine learning in APOGEE. Unsupervised spectral classification with K-means 2018A&A...612A..98G
    Disk stars in the Milky Way detected beyond 25 kpc from its center 2018A&A...612L...8L
    The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment 2018ApJS..235...42A
    Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67 2018ApJ...857...14S
    The Metal-poor non-Sagittarius (?) Globular Cluster NGC 5053: Orbit and Mg, Al, and Si Abundances 2018ApJ...855...38T
    J0023+0307: A Mega Metal-poor Dwarf Star from SDSS/BOSS 2018ApJ...854L..34A
    Stellar Multiplicity Meets Stellar Evolution and Metallicity: The APOGEE View 2018ApJ...854..147B
    A view of the H-band light-element chemical patterns in globular clusters under the AGB self-enrichment scenario 2018MNRAS.475.3098D
    An UXor among FUors: Extinction-related Brightness Variations of the Young Eruptive Star V582 Aur 2018ApJ...853...28A
    A photometric study of globular clusters observed by the APOGEE survey 2018MNRAS.475.1633M
    Disentangling the Galactic Halo with APOGEE. I. Chemical and Kinematical Investigation of Distinct Metal-poor Populations 2018ApJ...852...49H
    Disentangling the Galactic Halo with APOGEE. II. Chemical and Star Formation Histories for the Two Distinct Populations 2018ApJ...852...50F
    The Bulge Metallicity Distribution from the APOGEE Survey 2018ApJ...852...91G

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