Rotating massive O stars with non-spherical 2D winds

Abstract

We present solutions for the velocity field and mass-loss rates for 2D axisymmetric outflows, as well as for the case of mass accretion through the use of the Lambert W-function. For the case of a rotating radiation-driven wind the velocity field is obtained analytically using a parameterised description of the line acceleration that only depends on radius r at any given latitude $\theta$. The line acceleration g(r) is obtained from Monte-Carlo multi-line radiative transfer calculations. The critical/sonic point of our equation of motion varies with latitude $\theta$. Furthermore, an approximate analytical solution for the supersonic flow of a rotating wind is derived, which is found to closely resemble the exact solution. For the simultaneous solution of the mass-loss rate and velocity field, we use the iterative method of our 1D method extended to the non-spherical 2D case. We apply the new theoretical expressions with our iterative method to the stellar wind from a differentially rotating 40 $M_{sun}$ O5-V main sequence star as well as to a 60 $M_{sun}$ O-giant star, and we compare our results to previous studies that are extensions of the Castor et al. (1975, ApJ, 195, 157) CAK formalism. Next, we account for the effects of oblateness and gravity darkening. Our numerical results predict an equatorial decrease of the mass-loss rate, which would imply that (surface-averaged) total mass-loss rates are lower than for the spherical 1D case, in contradiction to the Maeder & Meynet (2000, A&A, 361, 159) formalism that is oftentimes employed in stellar evolution calculations for rotating massive stars. To clarify the situation in nature we discuss observational tests to constrain the shapes of large-scale 2D stellar winds.

20 pages, 4 figures, 7 tables, accepted for publication in A&A, (one corrected sentence in sect. 4.1.), a generalization of arXiv paper: arXiv:0810.1901

References in corpus (7)

• Pre-Supernova Evolution of Massive Single and Binary Stars
• Mass loss from hot massive stars
• Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit
• A consistent solution for the velocity field and mass-loss rate of massive stars
• The Dual-Axis Circumstellar Environment of the Type IIn Supernova 1997eg
• Spectropolarimetry of the Type IIb Supernova 2001ig
• A New Mechanism for Polarizing Light from Obscured Stars

Cited by in corpus (11)

• The evolution of rotating very massive stars with LMC composition
• Winds from stripped low-mass Helium stars and Wolf-Rayet stars
• Monte Carlo Radiative Transfer
• The effects of surface fossil magnetic fields on massive star evolution: II. Implementation of magnetic braking in MESA and implications for the evolution of surface rotation in OB stars
• Modeling the early evolution of massive OB stars with an experimental wind routine
• Critical angular velocity and anisotropic mass loss of rotating stars with radiation-driven winds
• Mass-loss rates of Very Massive Stars
• Centrifugally Driven Mass Loss and Outbursts of Massive Stars
• $\Omega$-Slow Solutions and Be Star Disks
• HST/COS Spectra of the Wind Lines of VFTS 102 and 285
• Analytical Solutions for Radiation-Driven Winds in Massive Stars. I: The Fast Regime