A Revised Geometry for the Magnetic Wind ofθ1Orionis C

Theta^1 Ori is thought to be a hot analog of Bp variables because its opticaland UV line and X-ray continuum fluxes modulate regularly over themagnetic/rotational period. A flattened magnetosphere surrounding co-rotateswith these stars, producing a periodic modulation of emission and absorptioncomponents of the UV resonance lines, as well as of optical H and He lines. Inthis paper we examine these modulations in detail and point out that thefar-blue and near-red wings of C IV and N V resonance lines exhibitanticorrelated modulations, causing mild flux elevations at moderate redshiftsat edge-on phase (phi=0.5). However, the lines do not exhibit rest-frameabsorption features, the usual signatures of cool static disks surrounding Bpstars. We suggest that this behavior can be explained by the existence of twogeometrically distinct wind regions separated by the local magnetic Alfvenradius. Wind streams emerging outside this point are forced outward byradiative forces and eventually expand outward radially to infinity - thismatter produces the far-blue wing absorptions at phi=0.5. Interior streamsfollow closed loops and collide at the magnetic equator with counterstreams.There they coalesce and fall back to the star along their original field lines- these are responsible for mild emissions at this same phase. The rapidcirculation of the interior wind component back to the star is responsible forthe absence of static disk features.Comment: 7 figure