论文标题
球状簇中的恒星碰撞：多个恒星种群的起源
Stellar collisions in globular clusters: the origin of multiple stellar populations
论文作者
论文摘要
两代恒星G1和G2通常填充银河系球状簇（GCS）。 G2恒星的起源尚不清楚。我们发现了GC特征之间的两个经验依赖性，这可以通过G2主序列（MS）恒星的形成来解释，这是由于其原始对应物的碰撞\合并（G1）。也暗示了G2恒星和奇特物体（如LMXB和毫秒脉冲星）的类似起源。的确，我们发现G1红色巨人（$ n_ {g1}/n_ {tot} $）与51 GC之间的G1红色巨头（$ n_ {g1}/n_ {tot} $）之间的抗相关性很大（> 99,9％）。此外，类似银河系的初始质量功能（IMF）需要至少约50％的位于质量范围[0.1-0.5] $ m \ odot $的MS星星。与群集质量损失不同，出色的碰撞\通过将它们转换为更大的G2恒星来保留这些G1恒星，主要是M_MS> 0.5 $ M \ odot $。此过程加上降低的相对质量损失，而GC质量的增加意味着在更大的GC中，较小的GC（$ n_ {g1}/n_ {tot} $）具有较浅的当今MF。从35个GC的数据中，我们发现，这种反相关在12个最大的GC（$ M_ {GC}> 10^{5.3} $）中的置信水平（Spearman的相关性）为98.3％（Spearman的相关性），并且在12个最不重要的GCS（$ m_} $ _ {GC} <10^1^1^<10^1^<10^$ _1的置信水平为89％。与一些GC中的红色巨型分支相比，在MS底部观察到的G1和G2星的其他级分与提出的情况一致。
Two generations of stars, G1 and G2, typically populate Galactic globular clusters (GCs). The origin of G2 stars is unclear. We uncover two empirical dependencies between GC characteristics, which can be explained by the formation of G2 Main-Sequence (MS) stars due to collision\merging of their primordial counterparts (G1). A similar genesis of both G2 stars and peculiar objects like LMXBs and millisecond pulsars is also implied. Indeed, we find a significant (at a confidence level > 99,9%) anti-correlation between the fraction of G1 red giants ($N_{G1}/N_{tot}$) and stellar encounter rates among 51 GCs. Moreover, a Milky Way-like initial mass function (IMF) requires at least ~50% of MS stars located in the mass range [0.1-0.5] $M\odot$. Unlike cluster mass loss, stellar collisions\merging retain these G1 stars by converting them into more massive G2 ones, with mainly M_ms > 0.5 $M\odot$. This process coupled with a decreasing relative mass loss with increasing GC masses implies a smaller ($N_{G1}/N_{tot}$) in more massive GCs with a shallower present day MF. From data for 35 GCs, we find that such an anti-correlation is significant at 98.3% confidence level (Spearman's correlation) for 12 most massive GCs ($M_{GC} > 10^{5.3}$) and it is at a confidence level of 89% for the 12 least massive GCs ($M_{GC} < 10^{5.1} M_\odot$). Other fractions of G1 and G2 stars observed at the bottom of the MS as compared with the red giant branch in a few GCs are consistent with the scenario proposed.
