Abstract INTEGRAL IBIS/ISGRI 18–60 keV observations of SS433 performed in 2003–2011 enabled for the first time the hard X-ray phase-resolved orbital and precessional light curves and spectra to be constructed. The spectra can be fitted by a power-law with photon index ≃ 3.8 and remain almost constant while the X-ray flux varies by a factor of a few. This suggests that the hard X-ray emission in SS433 is produced not in relativistic jets but in an extended quasi-isothermal hot ‘corona’ surrounding central parts of a supercritical accretion disc. Regular variations of the hard X-ray flux in SS433 exhibit, on top of the orbital and precessional variability, a nutational variability with a period of ~ 6.29 d. For the first time, a joint analysis of the broadband 18–60 keV orbital and precessional light curves was performed in the model that assumes a significant Roche lobe overfilling by the optical star, up to its filling the outer Lagrangian surface enabling mass loss through the outer Lagrangian L2 point. From this modeling, the relativistic-to-optical component mass ratio q = M x / M v ≳ 0.4 ÷ 0.8 is estimated. An analysis of the observed long-term stability of the orbital period of SS433 with an account of the recent observations of SS433 by the VLTI GRAVITY interferometer enabled an independent mass ratio estimate q > 0.6. This estimate in combination with the radial velocity semi-amplitude for stationary He II emission, K x = 168 ± 18 km s − 1 (Hillwig et al., 2004) suggest the optical component mass in SS433 Mv > 12 M⊙. Thus, the mass of the relativistic component in SS433 is Mx > 7 M⊙, which is close to the mean mass of black holes in X-ray binaries ( ~ 8 M⊙). The large binary mass ratio in SS433 allows us to understand why there is no common envelope in this binary at the secondary mass transfer evolutionary stage and the system remains semi-detached (van den Heuvel et al., 2017). We also discuss unsolved issues and outline prospects for further study of SS433.

中文翻译：

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SS433：处于高级进化阶段的大质量X射线双星

摘要 2003-2011 年对 SS433 进行的 IBIS/ISGRI 18-60 keV INTEGRAL IBIS/ISGRI 观测首次实现了硬 X 射线相位分辨轨道和岁差光曲线和光谱的构建。光谱可以通过光子指数 ≃ 3.8 的幂律拟合，并且几乎保持不变，而 X 射线通量变化几倍。这表明 SS433 中的硬 X 射线发射不是在相对论喷流中产生的，而是在超临界吸积盘中心部分周围的扩展准等温热“日冕”中产生的。除了轨道和岁差变化之外，SS433 中硬 X 射线通量的规则变化还表现出周期约为 6.29 天的章动变化。首次，在该模型中对宽带 18-60 keV 轨道和岁差光变曲线进行了联合分析，该模型假设光学星存在显着的罗氏瓣过度填充，直至填充外拉格朗日表面，从而使质量通过外拉格朗日 L2 点损失。根据该模型，估计相对论与光学组件的质量比 q = M x / M v ≳ 0.4 ÷ 0.8。对观测到的 SS433 轨道周期长期稳定性的分析，并结合 VLTI GRAVITY 干涉仪最近对 SS433 的观测结果，得出了独立的质量比估计值 q > 0.6。该估计与静止 He II 发射的径向速度半振幅 K x = 168 ± 18 km s − 1 (Hillwig et al., 2004) 相结合，表明 SS433 Mv > 12 M⊙ 中的光学分量质量。因此，SS433中相对论分量的质量为Mx > 7 M⊙，接近X射线双星中黑洞的平均质量（~8 M⊙）。SS433 中的大二元质量比使我们能够理解为什么在二次传质演化阶段该二元中没有共同的包络，并且系统保持半分离（van den Heuvel 等，2017）。我们还讨论了未解决的问题并概述了进一步研究 SS433 的前景。