On the origin of variable structures in the winds of hot luminous stars

Abstract

Examination of the temporal variability properties of several strong optical recombination lines in a large sample of Galactic Wolf-Rayet (WR) stars reveals possible trends, especially in the more homogeneous WC than the diverse WN subtypes, of increasing wind variability with cooler subtypes. This could imply that a serious contender for the driver of the variations is stochastic, magnetic subsurface convection associated with the 170 kK partial-ionization zone of iron, which should occupy a deeper and larger zone of greater mass in cooler WR subtypes. This empirical evidence suggests that the heretofore proposed ubiquitous driver of wind variability, radiative instabilities, may not be the only mechanism playing a role in the stochastic multiple small-scaled structures seen in the winds of hot luminous stars. In addition to small-scale stochastic behaviour, subsurface convection guided by a global magnetic field with localized emerging loops may also be at the origin of the large-scale corotating interaction regions as seen frequently in O stars and occasionally in the winds of their descendant WR stars.

8 pages, 2 figures and 2 tables. Monthly Notices of the Royal Astronomical Society 2013

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• The Effects of Magnetic Fields on the Dynamics of Radiation Pressure Dominated Massive Star Envelopes
• The chaotic wind of WR 40 as probed by BRITE
• Clumping in the Winds of Wolf-Rayet Stars
• The search for magnetic fields in two Wolf-Rayet stars and the discovery of a variable magnetic field in WR55
• A multi-wavelength search for intrinsic linear polarization in Wolf-Rayet winds
• From pulsar scintillations to coronal heating: discontinuities in magnetohydrodynamics
• Constraints on Clumps in the Representative Wind of the WN8 Wolf-Rayet star HD96548 = WR40 with Simultaneous Broadband Light and Linear-Polarisation Variability
• Structure formation in O-type stars and Wolf-Rayet stars