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

  • The ELM Survey. IV. 24 White Dwarf Merger Systems

    We present new radial velocity and X-ray observations of extremely low mass (ELM, ~0.2 M &sun;) white dwarf (WD) candidates in the Sloan Digital Sky Survey Data Release 7 area. We identify seven new binary systems with 1-18 hr orbital periods. Five of the systems will merge due to gravitational wave radiation within 10 Gyr, bringing the total

    Kilic, Mukremin et al.

    Advertised on:

    6
    2012
  • A 12 Minute Orbital Period Detached White Dwarf Eclipsing Binary

    We have discovered a detached pair of white dwarfs (WDs) with a 12.75 minute orbital period and a 1315 km s-1 radial velocity amplitude. We measure the full orbital parameters of the system using its light curve, which shows ellipsoidal variations, Doppler boosting, and primary and secondary eclipses. The primary is a 0.25 M sun tidally distorted

    Brown, Warren R. et al.

    Advertised on:

    8
    2011
  • Granulation Signatures in the Spectrum of the Very Metal-poor Red Giant HD 122563

    A very high resolution (R = λ/Δλ = 200, 000), high signal-to-noise ratio (S/N ~= 340) blue-green spectrum of the very metal-poor ([Fe/H] ~= -2.6) red giant star HD 122563 has been obtained by us at McDonald Observatory. We measure the asymmetries and core wavelengths of a set of unblended Fe I lines covering a wide range of line strength. Line

    Ramírez, I. et al.

    Advertised on:

    12
    2010

Talks related

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