Chemical Abundances in Stars

Start year
2010
Organizational Unit
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
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

Publications related

  • New ATLAS9 and MARCS Model Atmosphere Grids for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)

    We present a new grid of model photospheres for the SDSS-III/APOGEE survey of stellar populations of the Galaxy, calculated using the ATLAS9 and MARCS codes. New opacity distribution functions were generated to calculate ATLAS9 model photospheres. MARCS models were calculated based on opacity sampling techniques. The metallicity ([M/H]) spans from

    Mészáros, Sz. et al.

    Advertised on:

    10
    2012
  • SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way, and Extra-Solar Planetary Systems

    Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide

    Eisenstein, Daniel J. et al.

    Advertised on:

    9
    2011
  • The merger rate of extremely low mass white dwarf binaries: links to the formation of AM CVn stars and underluminous supernovae

    We study a complete, colour-selected sample of double-degenerate binary systems containing extremely low mass (ELM) ≤0.25 M&sun; white dwarfs (WDs). We show, for the first time, that Milky Way disc ELM WDs have a merger rate of approximately 4 × 10-5 yr-1 due to gravitational wave radiation. The merger end product depends on the mass ratio of the

    Brown, Warren R. et al.

    Advertised on:

    2
    2011

Talks related

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