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Dainis Dravins

Dainis Dravins

Professor emeritus

Dainis Dravins

Wavelength shifts in solar-type spectra

Author

  • Dainis Dravins
  • Lennart Lindegren
  • Hans-Günter Ludwig
  • Søren Madsen

Summary, in English

Spectral-line displacements away from the wavelengths naively expected from the Doppler shift caused by stellar radial motion may originate as convective shifts (correlated velocity and brightness patterns in the photosphere), as gravitational redshifts, or perhaps be induced by wave motions. Absolute lineshifts, in the past studied only for the Sun, are now accessible also for other stars thanks to astrometric determination of stellar radial motion, and spectrometers with accurate wavelength calibration. Comparisons between spectroscopic apparent radial velocities and astrometrically determined radial motions reveal greater spectral blueshifts in F-type stars than in the Sun (as theoretically expected from their more vigorous convection), further increasing in A-type stars (possibly due to atmospheric shockwaves). Work is in progress to survey the spectra of the Sun and several solar-type stars for "unblended" photospheric lines of most atomic species with accurate laboratory wavelengths available. One aim is to understand the ultimate information content of stellar spectra, and in what detail it will be feasible to verify models of stellar atmospheric hydrodynamics. These may predict bisectors and shifts for widely different classes of lines, but there will not result any comparison with observations if such lines do not exist in real spectra, or are too blended for meaningful measurement. An important near-future development to enable a further analysis of stellar surface structure will be the study of wavelength variations across spatially resolved stellar disks, e.g., the center-to-limb wavelength changes along a stellar diameter, and their spatially resolved time variability.

Department/s

  • Lund Observatory - Has been reorganised

Publishing year

2005

Language

English

Pages

113-119

Publication/Series

European Space Agency, (Special Publication) ESA SP

Volume

560

Document type

Conference paper

Publisher

European Space Agency

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • Radial velocities
  • Line profiles
  • Photiospheres
  • Wavelength

Conference name

13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun

Conference date

2004-07-05 - 2004-07-09

Conference place

Hamburg, Germany

Status

Published

ISBN/ISSN/Other

  • ISSN: 0379-6566
  • ISSN: 1609-042X