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 SEGUE K Giant Survey. II. A Catalog of Distance Determinations for the SEGUE K Giants in the Galactic Halo 2014ApJ...784..170X
    Discovery of Two Rare Rigidly Rotating Magnetosphere Stars in the APOGEE Survey 2014ApJ...784L..30E
    The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment 2014ApJS..211...17A
    ESPRESSO: The next European exoplanet hunter 2014AN....335....8P
    Identification of red supergiants in nearby galaxies with mid-IR photometry 2014A&A...562A..75B
    New Red Jewels in Coma Berenices 2014ApJ...782...61T
    Doppler imaging of the double-lined active binary V824 Ara 2013AN....334..976K
    Hypervelocity Star Candidates in the SEGUE G and K Dwarf Sample 2014ApJ...780....7P
    RATS-Kepler - a deep high-cadence survey of the Kepler field 2014MNRAS.437..132R
    Infrared Laboratory Oscillator Strengths of Fe I in the H-band 2013ApJ...779...17R
    The SDSS-III APOGEE Radial Velocity Survey of M Dwarfs. I. Description of the Survey and Science Goals 2013AJ....146..156D
    Discovery of a Dynamical Cold Point in the Heart of the Sagittarius dSph Galaxy with Observations from the APOGEE Project 2013ApJ...777L..13M
    Calibrations of Atmospheric Parameters Obtained from the First Year of SDSS-III APOGEE Observations 2013AJ....146..133M
    The Open Cluster Chemical Analysis and Mapping Survey: Local Galactic Metallicity Gradient with APOGEE Using SDSS DR10 2013ApJ...777L...1F
    The Protoplanetary Disks in the Nearby Massive Star-forming Region Cygnus OB2 2013ApJ...773..135G
    Very Low Mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. IV. A Candidate Brown Dwarf or Low-mass Stellar Companion to HIP 67526 2013AJ....146...65J
    Short-duration high-amplitude flares detected on the M dwarf star KIC 5474065 2013MNRAS.434.2451R
    Target Selection for the Apache Point Observatory Galactic Evolution Experiment (APOGEE) 2013AJ....146...81Z
    A PCA approach to stellar effective temperatures 2013A&A...553A..95M
    The ELM Survey. V. Merging Massive White Dwarf Binaries 2013ApJ...769...66B
    Very Low Mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. V. A Low Eccentricity Brown Dwarf from the Driest Part of the Desert, MARVELS-6b 2013AJ....145..155D
    A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself to be a Very Long Period, Highly Eccentric Spectroscopic Stellar Binary 2013AJ....145..139M
    Very Metal-poor Stars in the Outer Galactic Bulge Found by the APOGEE Survey 2013ApJ...767L...9G
    On the interpolation of model atmospheres and high-resolution synthetic stellar spectra 2013MNRAS.430.3285M
    Exploring the circumstellar environment of the young eruptive star V2492 Cygni 2013A&A...551A..62K
    Chemical Abundances in Field Red Giants from High-resolution H-band Spectra Using the APOGEE Spectral Linelist 2013ApJ...765...16S
    Convective line shifts for the Gaia RVS from the CIFIST 3D model atmosphere grid 2013A&A...550A.103A
    Oxygen Abundances in Nearby FGK Stars and the Galactic Chemical Evolution of the Local Disk and Halo 2013ApJ...764...78R
    Very-low-mass Stellar and Substellar Companions to Solar-like Stars from Marvels. III. A Short-period Brown Dwarf Candidate around an Active G0IV Subgiant 2013AJ....145...20M
    Automated Unsupervised Classification of the Sloan Digital Sky Survey Stellar Spectra using k-means Clustering 2013ApJ...763...50S
    The Metallicity Distribution Functions of SEGUE G and K Dwarfs: Constraints for Disk Chemical Evolution and Formation 2012ApJ...761..160S
    The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey 2012ApJS..203...21A
    Stars and brown dwarfs in the σ Orionis cluster. III. OSIRIS/GTC low-resolution spectroscopy of variable sources 2012A&A...546A..59C
    Observation and modelling of main-sequence star chromospheres - XIX. FIES and FEROS observations of dM1 stars 2012MNRAS.426.1591H
    The Milky Way's Circular-velocity Curve between 4 and 14 kpc from APOGEE data 2012ApJ...759..131B
    The shortest period detached binary white dwarf system 2011MNRAS.413L.101K
    The SEGUE Stellar Parameter Pipeline. V. Estimation of Alpha-element Abundance Ratios from Low-resolution SDSS/SEGUE Stellar Spectra 2011AJ....141...90L
    The merger rate of extremely low mass white dwarf binaries: links to the formation of AM CVn stars and underluminous supernovae 2011MNRAS.411L..31B
    The ELM Survey. IV. 24 White Dwarf Merger Systems 2012ApJ...751..141K
    The ELM Survey. III. A Successful Targeted Survey for Extremely Low Mass White Dwarfs 2012ApJ...744..142B

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