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Intrinsic spectral blueshifts in rapidly rotating stars?

Madsen, Søren LU ; Dravins, Dainis LU ; Ludwig, Hans-Günter LU and Lindegren, Lennart LU (2003) In Astronomy & Astrophysics 411(3). p.581-586
Abstract
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... (More)
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). (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
methods: data analysis, techniques: astrometry, spectroscopy, radial velocities, stars: rotation, open clusters and associations: general
in
Astronomy & Astrophysics
volume
411
issue
3
pages
581 - 586
publisher
EDP Sciences
external identifiers
  • wos:000186571300035
  • scopus:0344513387
ISSN
0004-6361
DOI
10.1051/0004-6361:20031396
language
English
LU publication?
yes
id
f6fee6e4-fc73-4578-b51e-764db3877eec (old id 130445)
date added to LUP
2007-07-13 14:09:15
date last changed
2017-01-01 07:08:33
@article{f6fee6e4-fc73-4578-b51e-764db3877eec,
  abstract     = {Spectroscopic radial velocities for several nearby open clusters suggestthat spectra of (especially earlier-type) rapidly rotating stars aresystematically blueshifted by 3 km s&lt;SUP&gt;-1&lt;/SUP&gt; 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).},
  author       = {Madsen, Søren and Dravins, Dainis and Ludwig, Hans-Günter and Lindegren, Lennart},
  issn         = {0004-6361},
  keyword      = {methods: data analysis,techniques: astrometry,spectroscopy,radial velocities,stars: rotation,open clusters and associations: general},
  language     = {eng},
  number       = {3},
  pages        = {581--586},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {Intrinsic spectral blueshifts in rapidly rotating stars?},
  url          = {http://dx.doi.org/10.1051/0004-6361:20031396},
  volume       = {411},
  year         = {2003},
}