A rigidly rotating magnetosphere model for circumstellar emission from magnetic OB stars
A rigidly rotating magnetosphere model for circumstellar emission from magnetic OB stars
复制标题
磁性 OB 星星周发射的刚性旋转磁层模型
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
S. Owocki
中科院分区：
文献类型：
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作者：
R. Townsend;S. Owocki
我们提出了一种半解析方法来模拟具有与旋转轴成任意角度倾斜的强偶极子磁场的旋转热星的星周辐射。通过假设从恒星驱动的物质(例如，在风的外流中)被强迫保持严格的刚体共转的刚体极限，我们能够求解沿每条场线的有效离心势和引力势，从而确定物质容易积累的势极小值的位置。应用辐射驱动恒星风表面质量通量的基本标度，我们计算了一旦喷出的等离子体沿场线进入流体静力层结时所获得的星周密度分布。由此产生的累积面类似于一个刚性旋转的翘曲圆盘，倾斜使其平均表面法线位于旋转轴和磁轴之间。利用等离子体发射率的一个简单模型，我们计算了圆盘的时间分辨合成线谱。初步的比较表明，与观测到的σ或E等磁BP星的巴尔默线发射轮廓的旋转相位变化相一致，这是一个令人鼓舞的水平。
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.