The projected rotational velocity distribution of a sample of OB stars from a calibration based on synthetic he i lines

Simone Daflon, Katia Cunha, Francisco X. De Araújo, Sidney Wolff, Norbert Przybilla

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23 Scopus citations


We derive projected rotational velocities (v sin i) for a sample of 156 Galactic OB star members of 35 clusters, H II regions, and associations. The He i lines at 4026, 4388, and 4471 Â were analyzed in order to define a calibration of the synthetic He I full widths at half-maximum (FWHMs) versus stellar v sin i. A grid of synthetic spectra of He I line profiles was calculated in non-LTE using an extensive helium model atom and updated atomic data. The v sin i values for all stars were derived using the He I FWHM calibrations, but also, for those target stars with relatively sharp lines, v sin i values were obtained from best-fit synthetic spectra of up to 40 lines of C II, N II, O II, Al III, Mg II, Si III, and S III. This calibration is a useful and efficient tool for estimating the projected rotational velocities of O9-B5 mainsequence stars. The distribution of v sin i for an unbiased sample of early B stars in the unbound association Cep OB2 is consistent with the distribution reported elsewhere for other unbound associations.

Original languageEnglish (US)
Pages (from-to)1570-1578
Number of pages9
JournalAstronomical Journal
Issue number4
StatePublished - 2007
Externally publishedYes


  • Line: profiles
  • Stars: early-type
  • Stars: rotation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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