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Dainis Dravins. Profile photo.

Dainis Dravins

Professor emeritus

Dainis Dravins. Profile photo.

Intrinsic spectral blueshifts in rapidly rotating stars?

Author

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

Summary, in English

Spectroscopic radial velocities for several nearby open clusters suggestthat spectra of (especially earlier-type) rapidly rotating stars aresystematically blueshifted by 3 km s<SUP>-1</SUP> or more, relative tothe spectra of slowly rotating ones. Comparisons with astrometricallydetermined radial motions in the Hyades suggests this to be an absoluteblueshift, relative to wavelengths naively expected from stellar radialmotion and gravitational redshift. Analogous trends are seen also inmost other clusters studied (Pleiades, Coma Berenices, Praesepe, alphaPersei, IC 2391, NGC 6475, IC 4665, NGC 1976 and NGC 2516). Possiblemechanisms are discussed, including photospheric convection, stellarpulsation, meridional circulation, and shock-wave propagation, as wellas effects caused by template mismatch in determining wavelengthdisplacements. For early-type stars, a plausible mechanism is shock-wavepropagation upward through the photospheric line-forming regions. Suchwavelength shifts thus permit studies of certain types of stellaratmospheric dynamics and - irrespective of their cause - may influencededuced open-cluster membership (when selected from common velocity) anddeduced cluster dynamics (some types of stars might show fortuitousvelocity patterns).

Department/s

  • Lund Observatory

Publishing year

2003

Language

English

Pages

581-586

Publication/Series

Astronomy & Astrophysics

Volume

411

Issue

3

Document type

Journal article

Publisher

EDP Sciences

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • methods: data analysis
  • techniques: astrometry
  • spectroscopy
  • radial velocities
  • stars: rotation
  • open clusters and associations: general

Status

Published

ISBN/ISSN/Other

  • ISSN: 0004-6361