标题： 风包相互作用作为光亮蓝变星缓慢周期性亮度变化的起因 显示英文标题

标题： Wind-envelope interaction as the origin of the slow cyclic brightness variations of luminous blue variables

摘要： 光致蓝变星（LBVs）是高温、非常明亮的大质量恒星，其亮度、半径和光球温度在数年至数十年的时间尺度上表现出大的准周期性变化。这种被称为S Doradus循环的变异性，其物理起源一直难以捉摸。在这里，我们研究了接近爱丁顿极限的恒星包层结构中恒星风质量损失的反馈作用。我们进行了一次随时间变化的流体动力学恒星演化计算，应用了一个基于低于25 kK时质量损失率预测系统性增加的温度依赖性的恒星风质量损失方案。我们发现，当风的质量损失率超过一个明确的阈值时，风基条件的不连续变化会导致恒星包层的重新结构化。由此引起的剧烈半径和温度变化发生在膨胀包层的热时标内，反过来又导致质量损失的变化，从而逆转初始变化，形成一个没有稳定平衡配置的循环。我们的概念验证模型大致再现了S Doradus变异性典型的观测现象学。我们确定了触发不稳定的三个关键物理要素：接近爱丁顿极限的膨胀包层，在该温度范围内减少的不透明度不会导致流出加速，以及随着温度降低而增加的质量损失率，在此温度范围内超过临界阈值。我们的场景和模型提供了可检验的预测，并为恒星演化中LBV阶段的一致理论处理打开了大门，对它们作为单星或双星系统的进一步演化有影响。 显示英文摘要

摘要： Luminous blue variables (LBVs) are hot, very luminous massive stars displaying large quasi-periodic variations in brightness, radius,and photospheric temperature, on timescales of years to decades. The physical origin of this variability, called S Doradus cycle after its prototype, has remained elusive. Here, we study the feedback of stellar wind mass-loss on the envelope structure in stars near the Eddington limit. We perform a time-dependent hydrodynamic stellar evolutionary calculation, applying a stellar wind mass-loss prescription with a temperature-dependence inspired by the predicted systematic increase in mass-loss rates below 25 kK. We find that when the wind mass-loss rate crosses a well-defined threshold, a discontinuous change in the wind base conditions leads to a restructuring of the stellar envelope. The induced drastic radius and temperature changes, which occur on the thermal timescale of the inflated envelope, impose in turn mass-loss variations that reverse the initial changes, leading to a cycle that lacks a stationary equilibrium configuration. Our proof-of-concept model broadly reproduces the typical observational phenomenology of the S Doradus variability. We identify three key physical ingredients needed to trigger the instability: inflated envelopes in close proximity to the Eddington limit, a temperature range where decreasing opacities do not lead to an accelerating outflow, and a mass-loss rate that increases with decreasing temperature, crossing a critical threshold value within this temperature range. Our scenario and model provide testable predictions, and open the door for a consistent theoretical treatment of the LBV phase in stellar evolution, with consequences for their further evolution as single stars or in binary systems.