Spectroscopic and physical parameters of Galactic O-type stars. II. Observational constraints on projected rotational and extra broadening velocities as a function of fundamental parameters and stellar evolution

Abstract

Rotation is of key importance for the evolution of hot massive stars, however, the rotational velocities of these stars are difficult to determine. Based on our own data for 31 Galactic O stars and incorporating similar data for 86 OB supergiants from the literature, we aim at investigating the properties of rotational and extra line-broadening as a function of stellar parameters and at testing model predictions about the evolution of stellar rotation. Fundamental stellar parameters were determined by means of the code FASTWIND. Projected rotational and extra broadening velocities originate from a combined Ft + GOF method. Model calculations published previously were used to estimate the initial evolutionary masses. The sample O stars with Minit > 50 Msun rotate with less that 26% of their break-up velocity, and they also lack objects with v sin i < 50 km/s. For the stars with Minit > 35 Msun on the hotter side of the bi-stability jump, the observed and predicted rotational rates agree quite well; for those on the cooler side of the jump, the measured velocities are systematically higher than the predicted ones. In general, the derived extra broadening velocities decrease toward cooler Teff, whilst for later evolutionary phases they appear, at the same v sin i, higher for high-mass stars than for low-mass ones. None of the sample stars shows extra broadening velocities higher than 110 km/s. For the majority of the more massive stars, extra broadening either dominates or is in strong competition with rotation. Conclusions: For OB stars of solar metallicity, extra broadening is important and has to be accounted for in the analysis. When appearing at or close to the zero-age main sequence, most of the single and more massive stars rotate slower than previously thought. Model predictions for the evolution of rotation in hot massive stars may need to be updated.

15 pages, 10 figures, accepted for publication in A & A

References in corpus (14)

• Pre-Supernova Evolution of Massive Single and Binary Stars
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• The VLT-FLAMES Tarantula Survey XII. Rotational velocities of the single O-type stars
• The VLT-FLAMES survey of massive stars: atmospheric parameters and rotational velocity distributions for B-type stars in the Magellanic Clouds
• Bright OB stars in the Galaxy IV. Stellar and wind parameters of early to late B supergiants
• Quantitative studies of the optical and UV spectra of Galactic early B supergiants I. Fundamental parameters
• The VLT-FLAMES Survey of Massive Stars: Stellar parameters and rotational velocities in NGC3293, NGC4755 and NGC6611
• Abundance analysis of prime B-type targets for asteroseismology I. Nitrogen excess in slowly-rotating beta Cephei stars
• Statistical properties of a sample of periodically variable B-type supergiants - Evidence for opacity-driven gravity-mode oscillations
• Nitrogen enrichment, boron depletion and magnetic fields in slowly-rotating B-type dwarfs
• Stellar Rotation: A Clue to the Origin of High Mass Stars?
• Wind structure of late B supergiants I. Multi-line analyses of near-surface and wind structure in HD 199 478 (B8 Iae)

Cited by in corpus (28)

• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• The spectroscopic Hertzsprung-Russell diagram
• The spectroscopic Hertzsprung-Russell diagram of Galactic massive stars
• The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars
• Towards a unified view of inhomogeneous stellar winds in isolated supergiant stars and supergiant high mass X-ray binaries
• The IACOB project. V. Spectroscopic parameters of the O-type stars in the modern grid of standards for spectral classification
• Spectroscopic and physical parameters of Galactic O-type stars. III. Mass discrepancy and rotational mixing
• The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars
• The Gaia-ESO Survey: calibration strategy
• On the use of the Fourier Transform to determine the projected rotational velocity of line-profile variable B stars
• The IACOB project. VII. The rotational properties of Galactic massive O-type stars revisited
• The VLT-FLAMES Tarantula Survey. XIII: On the nature of O Vz stars in 30 Doradus
• Observational consequences of turbulent pressure in the envelopes of massive stars
• The VLT-FLAMES Tarantula Survey XXV. Surface nitrogen abundances of O-type giants and supergiants
• The IACOB project. VI. On the elusive detection of massive O-type stars close to the ZAMS
• Fast & slow winds from supergiants and Luminous Blue Variables
• The deep OB star population in Carina from the VST Photometric H$\alpha$ Survey (VPHAS+)
• Interplay between pulsations and mass loss in the blue supergiant 55 Cygnus = HD 198478
• The rotation rates of massive stars: How slow are the slow ones?
• On the H$\alpha$ Behaviour of Blue Supergiants: Rise and Fall over the Bi-stability Jump
• Metal-Rich SX Phe stars in the Kepler Field
• Astrophysical parameters and orbital solution of the peculiar X-ray transient IGR J00370+6122
• The IACOB project XIV. New clues on the location of the TAMS in the massive star domain
• A clustered origin for isolated massive stars
• Polarized radio emission unveils the structure of the pre-supernova circumstellar magnetic field and the radio emission in SN1987A
• Spindown of massive main sequence stars in the Milky Way
• Micro-turbulence across the Hertzsprung-Russell diagram. Observational constrains for stars in the MW