Modelling O-star astrospheres with different relative speeds between the ISM and the star: 2D and 3D MHD model comparison
Modelling O-star astrospheres with different relative speeds between the ISM and the star: 2D and 3D MHD model comparison
复制标题
对 ISM 和恒星之间具有不同相对速度的 O 星天球层进行建模：2D 和 3D MHD 模型比较
DOI：
10.1051/0004-6361/202243525
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
K. Weis
中科院分区：
文献类型：
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作者：
L. R. Baalmann;K. Scherer;J. Kleimann;H. Fichtner;D. Bomans;K. Weis
语境。使用三维（3D）磁性流动力学（MHD）对天然平流的最先进模拟进行了模拟。恒星风（SW）与其周围星际介质（ISM）的天文圈相互作用只有在星际流入的速度高于快速磁通速度的情况下，才能产生弓形冲击。目标。研究了在ISM流入速度不同的速度下的天然球的差异，并评估了第三维的必要性。方法。 O-Star $ \ lambda $ cephei的模型天气际以四种不同的ISM流入速度计算在两维MHD中，其中一个几乎不快（Superfast），并且其中一个速度较慢（subfast）比快速的磁速速度。结果。 ISM流入速度的二维（2D）和3D模型高于快速磁通速度。但是，在没有可逼真的SW磁场可以建模的2D模型中，天体的下风结构会摇动。流体动力效应在磁场上没有明显主导的模型显示不对称，因此需要进行3D方法。慢速ISM流入的天体模拟的物理时期可以迅速超过相应恒星的寿命。迄今未观察到的结构已在Subfast 3D模型中下风。
Context. State of the art simulations of astrospheres are modelled using three-dimensional (3D) magnetohydrodynamics (MHD). An astrospheric interaction of a stellar wind (SW) with its surrounding interstellar medium (ISM) can only generate a bow shock if the speed of the interstellar inflow is higher than the fast magnetosonic speed. Aims. The differences of astrospheres at differing speeds of the ISM inflow are investigated, and the necessity of the third dimension in modelling is evaluated. Methods. The model astrosphere of the runaway O-star $\lambda$ Cephei is computed in both two- and three-dimensional MHD at four different ISM inflow speeds, one of which is barely faster (superfast) and one of which is slower (subfast) than the fast magnetosonic speed. Results. The two-dimensional (2D) and 3D models of astrospheres with ISM inflow speeds considerably higher than the fast magnetosonic speed are in good agreement. However, in 2D models, where no realistic SW magnetic field can be modelled, the downwind structures of the astrospheres vacillate. Models where hydrodynamic effects are not clearly dominant over the magnetic field show asymmetries, thus necessitating a 3D approach. The physical times of simulations of astrospheres with slow ISM inflows can swiftly exceed the lifetime of the corresponding star. A hitherto unobserved structure has been found downwind of the astrotail in the subfast 3D model.