A rigidly rotating magnetosphere model for circumstellar emission from magnetic OB stars
Abstract
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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2005
- DOI:
- 10.1111/j.1365-2966.2005.08642.x
- arXiv:
- arXiv:astro-ph/0408565
- Bibcode:
- 2005MNRAS.357..251T
- Keywords:
-
- stars: chemically peculiar;
- stars: early-type;
- stars: emission-line;
- Be;
- stars: magnetic fields;
- stars: mass-loss;
- stars: rotation;
- Astrophysics
- E-Print:
- 15 pages, 4 figures, submitted to MNRAS, revised version based on referee's remarks