Bibcode
Dufton, P. L.; Langer, N.; Dunstall, P. R.; Evans, C. J.; Brott, I.; de Mink, S. E.; Howarth, I. D.; Kennedy, M.; McEvoy, C.; Potter, A. T.; Ramírez-Agudelo, O. H.; Sana, H.; Simón-Díaz, S.; Taylor, W.; Vink, J. S.
Bibliographical reference
Astronomy and Astrophysics, Volume 550, id.A109, 12 pp.
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2
2013
Journal
Citations
119
Refereed citations
105
Description
Aims: Projected rotational velocities (vesini) have
been estimated for 334 targets in the VLT-FLAMES Tarantula Survey that
do not manifest significant radial velocity variations and are not
supergiants. They have spectral types from approximately O9.5 to B3. The
estimates have been analysed to infer the underlying rotational velocity
distribution, which is critical for understanding the evolution of
massive stars. Methods: Projected rotational velocities were
deduced from the Fourier transforms of spectral lines, with upper limits
also being obtained from profile fitting. For the narrower lined stars,
metal and non-diffuse helium lines were adopted, and for the broader
lined stars, both non-diffuse and diffuse helium lines; the estimates
obtained using the different sets of lines are in good agreement. The
uncertainty in the mean estimates is typically 4% for most targets. The
iterative deconvolution procedure of Lucy has been used to deduce the
probability density distribution of the rotational velocities.
Results: Projected rotational velocities range up to approximately 450
km s-1 and show a bi-modal structure. This is also present in
the inferred rotational velocity distribution with 25% of the sample
having 0 ≤ ve ≤ 100 km s-1 and the high
velocity component having ve ~ 250 km s-1. There
is no evidence from the spatial and radial velocity distributions of the
two components that they represent either field and cluster populations
or different episodes of star formation. Be-type stars have also been
identified. Conclusions: The bi-modal rotational velocity
distribution in our sample resembles that found for late-B and early-A
type stars. While magnetic braking appears to be a possible mechanism
for producing the low-velocity component, we can not rule out
alternative explanations.
Tables 3 and 4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/550/A109
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Sergio
Simón Díaz