论文标题
Schoenberg-Chandrasekhar限制的性质
The nature of the Schoenberg-Chandrasekhar limit
论文作者
论文摘要
我们提供了Schönberg-chandrasekhar（S-C）的彻底描述，这是当氦芯的分数达到临界值时，从核量表到热时间尺度的恒星演变的加速度，约为0.1。它发生在1.4至7 m $ _ \ odot $质量范围内，因为在核能中的核能源消失后无法保持热平衡。我们介绍了氢丰度，能量产生速率和恒星穿越该极限的温度的分布。我们确认严格的等温核存在急剧的S-C限制，但对于真正的恒星来说，它更加顺畅。核心的边界定义的方式对于此过渡的图像很重要。严格将核心定义为氦丰度接近零的区域，它发生在分数核心质量的延长范围内，约为0.03至0.11。 The cause of that is a gradual core contraction causing a correspondingly gradual loss of the core isothermality with the increasing core mass.另一方面，当使用允许核心中h丰度的定义时，发现S-C转变在大约0.07至0.11之间的分数核心质量处很清晰。尽管如此，它还是一个平稳的过渡，而不是急剧的限制。我们还搜索了该过渡的特定签名，并发现它与恒星半径首先减小，然后再次增加。我们已经考虑了S-C限制是否可以用作诊断限制X射线二进制的进化状态的诊断，但发现这种用途没有根据。
We present a comprehensive description of the Schönberg--Chandrasekhar (S--C) transition, which is an acceleration of the stellar evolution from the nuclear to the thermal time scales occurring when the fractional mass of the helium core reaches a critical value, about 0.1. It occurs in the 1.4 to 7 M$_\odot$ mass range due to impossibility of maintaining the thermal equilibrium after the nuclear energy sources in the core disappear. We present the distributions of the hydrogen abundance, the energy generation rate and the temperature for stars crossing that limit. We confirm that a sharp S--C limit is present for strictly isothermal cores, but it is much smoother for real stars. The way the boundary of the core is defined is important for the picture of this transition. With a strict definition of the core as the region where the helium abundance is close to null, it occurs in an extended range of the fractional core mass of roughly 0.03 to 0.11. The cause of that is a gradual core contraction causing a correspondingly gradual loss of the core isothermality with the increasing core mass. On the other hand, when using definitions allowing for some H abundance in the core, the S--C transition is found to be sharper, at the fractional core mass of between about 0.07 and 0.11. Still, it is more a smooth transition than a sharp limit. We have also searched for specific signatures of that transition, and found that it is associated with the stellar radius first decreasing and then increasing again. We have considered whether the S--C limit can be used as a diagnostic constraining the evolutionary status of accreting X-ray binaries, but found such uses unfounded.
