A rigidly rotating magnetosphere model for circumstellar emission from magnetic OB stars

By R. Townsend, S. Owocki. 2004

167 citations recorded by the source corpus.

We present a semi-analytical approach for modelling circumstellar emission from rotating hot stars with a strong dipole magnetic field tilted at an arbitrary angle to the rotation axis. By assuming the rigid-field limit in which material driven (e.g. in a wind outflow) from the star is forced to remain in strict rigid-body corotation, we are able to solve for the effective centrifugal-plus-gravitational potential along each field line, and thereby identify the location of potential minima where material is prone to accumulate. Applying basic scalings for the surface mass flux of a radiatively driven stellar wind, we calculate the circumstellar density distribution that obtains once ejected plasma settles into hydrostatic stratification along field lines. The resulting accumulation surface resembles a rigidly rotating, warped disc, tilted such that its average surface normal lies between the rotation and magnetic axes. Using a simple model of the plasma emissivity, we calculate time-resolved synthetic line spectra for the disc. Initial comparisons show an encouraging level of correspondence with the observed rotational phase variations of Balmer-line emission profiles from magnetic Bp stars such as σ Ori E.

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Citations in the corpus

The MiMeS survey of Magnetism in Massive Stars : magnetic analysis of the O-type stars (2016, background): “…the significance of magnetic fields in determining their wind structure (e.g. Shore & Brown 1990; Babel & Montmerle 1997; ud-Doula & Owocki 2002; Townsend & Owocki 2005), rotation (e.g. ud-Doula et al. 2009; Mikulášek et al. 2008; Townsend 2010), and evolution (e.g. Meynet et al. 2011; Maeder…”
The surprising magnetic topology of τ Sco: fossil remnant or dynamo output? (2006, unknown): “…variations are detected; Donati et al. 2001, 2002), but differs from HD 191612 and σ Ori E (for which eclipses of the continuum radiation by the magnetospheric plasma are observed, at levels of 0.04 and 0.15 mag, respectively; Walborn et al. 2004; Townsend & Owocki 2005; Donati et al. 2006).”
An investigation of the close environment of β Cephei with the VEGA/CHARA interferometer (2010, background): “…work based on dynamical modeling of the wind-magnetic-field interaction, however, indicates that the thick ring (in the X-ray domain) predicted by Babel & Montmerle (1997) would be unlikely to form around a star such as β Cep (Gagné et al. 2005; ud-Doula & Owocki 2002; Townsend & Owocki 2005).”
Mass loss from hot massive stars (2008, background): “For the limiting case of very high field strength, η∗ → ∞, Townsend and Owocki (2005) developed the alternative “rigidly rotating magnetosphere” model, originally designed to investigate the prototypical Bp star σ Ori E with B ∼ 104 G.”