论文标题
在潮汐流中创建/破坏超宽二进制文件
Creation/destruction of ultra-wide binaries in tidal streams
论文作者
论文摘要
本文使用统计和$ n $ body方法来探索一种新的机制，以形成具有极大分离的二进制恒星（$> 0.1 \，{\ rm pc} $），其起源知之甚少。在这里，超宽的二进制文件是通过将无关的恒星夹在破坏簇的潮汐流中而产生的。结果表明，（i）超宽二进制文件的形成不限于簇的生命，而是在祖细胞完全破坏祖细胞后继续进行，（ii）形成速率与潮汐尾巴的局部相位空间密度成比例，（iii）半轴轴分布量表，$ p（a）$ p（a）$ p（a）p（a）d a^1/d a^1/d a^1/d/l a^1/ ll a^1/ ll a^1/l ll a^1/ ll a^^ll a^1/l ll a^^ll a^^a^^ll a^^ll a^^a^{1/l ll a^^a^^ll a^^a^{1/ll d $，其中$ d $是平均星际距离，（vi）偏心分布接近热力，$ p（e）d e = 2 e d e $。由于其低结合能，超宽的二进制文件可能会被光滑的潮汐场和传递子结构所破坏。潮汐波动在平均场上占主导地位的时间尺度与团块的局部密度成反比。蒙特卡洛实验表明，要潮汐蒸发的二进制$ p（a）d a \ sim a \ sim a^{ - 1} d a $在$ a \ gtrsim a \ gtrsim a _ {\ rm peak} $，被称为Öpik的定律，与emai-major axis合并，该法律与时间相关，该峰值与时间相关。 t^{ - 3/4} $。相比之下，光滑的银河电位在潮汐半径上引入了急剧的截断，$ p（a）\ sim 0 $ at $ a \ gtrsim r_t $。年轻簇的扩展关系表明，大多数超宽二进制文件源于低质量系统的破坏。球状簇的流可能是数百种超宽二进制文件的发源地，使其成为理想的实验室，以探测银河晕圈中的块状。
This paper uses statistical and $N$-body methods to explore a new mechanism to form binary stars with extremely large separations ($> 0.1\,{\rm pc}$), whose origin is poorly understood. Here, ultra-wide binaries arise via chance entrapment of unrelated stars in tidal streams of disrupting clusters. It is shown that (i) the formation of ultra-wide binaries is not limited to the lifetime of a cluster, but continues after the progenitor is fully disrupted, (ii) the formation rate is proportional to the local phase-space density of the tidal tails, (iii) the semimajor axis distribution scales as $p(a)d a\sim a^{1/2}d a$ at $a\ll D$, where $D$ is the mean interstellar distance, and (vi) the eccentricity distribution is close to thermal, $p(e)d e= 2 e d e$. Owing to their low binding energies, ultra-wide binaries can be disrupted by both the smooth tidal field and passing substructures. The time-scale on which tidal fluctuations dominate over the mean field is inversely proportional to the local density of clumps. Monte-Carlo experiments show that binaries subject to tidal evaporation follow $p(a)d a\sim a^{-1}d a$ at $a\gtrsim a_{\rm peak}$, known as Öpik's law, with a peak semi-major axis that contracts with time as $a_{\rm peak}\sim t^{-3/4}$. In contrast, a smooth Galactic potential introduces a sharp truncation at the tidal radius, $p(a)\sim 0$ at $a\gtrsim r_t$. The scaling relations of young clusters suggest that most ultra-wide binaries arise from the disruption of low-mass systems. Streams of globular clusters may be the birthplace of hundreds of ultra-wide binaries, making them ideal laboratories to probe clumpiness in the Galactic halo.
