恒星风对不对准的Be/X射线双星吸积的抑制作用
Inhibition of Accretion by the Stellar Wind in Misaligned Be/X-ray Binaries
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中文总结 AI 辅助
研究不对准的Be/X射线双星中恒星风对吸积动力学的影响，利用解析模型比较风冲压压力与吸积流气体压力得出抑制条件，发现风驱动抑制对特定BeXRBs系统是合理机制，补充经典螺旋桨机制在特定情况的不足。
中文摘要 AI 辅助
Be/X射线双星（BeXRBs）是高质量X射线双星的一个主要子类。它们呈现间歇性X射线活动，X射线光度$L_X > 10^{36} {\rm erg s}^{-1}$，而大部分时间处于静止状态，$L_X < 10^{34} {\rm erg s}^{-1}$。BeXRBs通常因中子星诞生时的超新星踢而具有偏心轨道，这也可能使双星轨道轴与Be星自转轴不对准。当中子星从Be星赤道盘捕获气体时，形成的吸积盘通常相对于Be盘平面和双星轨道平面都有倾斜。本文利用解析风模型和盘模型，研究恒星风对不对准的BeXRBs吸积动力学的影响。通过比较风的冲压压力与吸积流的气体压力，得出恒星风强烈抑制吸积的条件，并将其应用于相关参数已确定或受限的BeXRBs样本。研究发现，对于轨道较宽、中子星自转较慢的系统，风驱动抑制是一种合理的吸积抑制机制，在经典螺旋桨机制效率低下的情况下尤其重要，特别是当吸积流热且低密度时，或者吸积率从爆发水平下降之后。
英文摘要
Be/X-ray binaries (BeXRBs) constitute a major subclass of high-mass X-ray binaries. They show intermittent X-ray activity with $L_X > 10^{36} {\rm erg s}^{-1}$, while remaining quiescent most of the time with $L_X < 10^{34} {\rm erg s}^{-1}$. BeXRBs generally have eccentric orbits as a result of supernova kicks when neutron stars were born. In these systems, the same kicks are also likely to make the binary orbital axis misaligned with the spin axis of the Be star. In such systems, when the neutron star captures gas from the equatorial disk of the Be star, the resulting accretion disk is in general tilted to both the Be disk plane and to the binary orbital plane. This raises an interesting possibility that in misaligned BeXRBs, the polar wind of the Be star collides with the accretion disk and significantly affects its structure by the large ram pressure. In this paper, we study the effects of the stellar wind on the accretion dynamics in misaligned BeXRBs. Using analytical wind and disk models, we first compare the wind's ram pressure with the gas pressures of the accretion flow to derive a condition for the stellar wind to strongly suppress accretion, and then apply the condition to a sample of BeXRBs whose relevant parameters are well determined or constrained. We find that wind-driven inhibition is a plausible mechanism for suppressing accretion in systems with slowly rotating neutron stars in wide orbits, where the classical propeller mechanism is expected to be inefficient. The effect is particularly important if the accretion flow is hot and low-density, or after the accretion rate has declined from the outburst level.
