论文标题

从极地圆盘上积聚到二进制

Accretion onto a binary from a polar circumbinary disc

论文作者

Smallwood, Jeremy L., Lubow, Stephen H., Martin, Rebecca G.

论文摘要

我们提供流体动力学模拟,以建模从极性圆盘上的吸积流到具有接近统一质量比($ Q = 0.83 $)的高偏心度($ e = 0.78 $)的二进制星系,作为二进制HD 98800 BABB的型号。我们将极地电圆盘积聚流与先前研究的共面情况进行了比较。在共面案例中,电路光盘变得偏心,积聚从占主导地位到一个二元成员到另一个二元成员。对于涉及高度偏心二进制的极性碟片,我们发现电圆盘保留了其最初低的偏心率,并且主要的恒星积聚速率始终与次级恒星积聚率大致相同。最近对具有极地圆盘的二进制HD 98800 BABB的观察结果已用于确定$ \ rmHα$通量从更明亮的组件中的值。从这个值中,我们推断出积聚率远低于典型的T牛tauri恒星。外伴侣HD 98800 A的怪异轨道将增生率提高到HD 98800 B上,每次底座通道后,$ \ sim 20 $ 20 $。我们的流体动力学模拟无法解释如此低的吸积率,除非圆盘粘度参数非常小,$α<10^{ - 5} $。对该系统的其他观察结果对检查这种低积聚率将很有用。

We present hydrodynamical simulations to model the accretion flow from a polar circumbinary disc onto a high eccentricity ($e=0.78$) binary star system with near unity mass ratio ($q=0.83$), as a model for binary HD 98800 BaBb. We compare the polar circumbinary disc accretion flow with the previously studied coplanar case. In the coplanar case, the circumbinary disc becomes eccentric and the accretion alternates from being dominant onto one binary member to the other. For the polar disc case involving a highly eccentric binary, we find that the circumbinary disc retains its initially low eccentricity and that the primary star accretion rate is always about the same as the secondary star accretion rate. Recent observations of the binary HD 98800 BaBb, which has a polar circumbinary disc, have been used to determine the value of the $\rm Hα$ flux from the brighter component. From this value, we infer that the accretion rate is much lower than for typical T Tauri stars. The eccentric orbit of the outer companion HD 98800 A increases the accretion rate onto HD 98800 B by $\sim 20$ per cent after each periastron passage. Our hydrodynamical simulations are unable to explain such a low accretion rate unless the disc viscosity parameter is very small, $α< 10^{-5}$. Additional observations of this system would be useful to check on this low accretion rate.

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