Accretion rates in hierarchical triple systems with discs
Accretion rates in hierarchical triple systems with discs
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DOI：
10.1093/mnras/stac1390
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发表时间：
2022-06-08
影响因子：
4.8
通讯作者：
Price, Daniel J.
中科院分区：
文献类型：
--
作者：
Ceppi, Simone;Cuello, Nicolas;Price, Daniel J.
年轻的多星系在其生命的最初几个MYR阶段，即原恒星和原行星阶段，共生了它们最后的大部分质量。先前的研究表明，在双星系统中，大部分被吸积的质量落在较轻的恒星上，从而演化为质量均衡。然而，年轻的恒星系统通常由两颗以上的恒星组成，预计这两颗恒星将处于分层结构。尽管它与天体物理有关，但等级系统中的差异吸积仍有待理解。在这项工作中，我们调查了双星中预期的吸积趋势是否适用于更高阶的倍数。我们对嵌入在吸积盘中的双星和三元系(HTS)进行了一组三维光滑粒子流体动力学模拟，其代码为Phantom。我们首次确定了HTS中的吸积趋势及其与双星的偏差。这些偏差可以用半解析公式来描述，这些偏差是由于小双星与来自外接三圆盘的流入物质的相互作用造成的。一般来说，较小的双星比与较小的双星质量相同的单星增加的质量更多。我们发现，在HT中，如果小双星比第三体重，标准的微分吸积情景(第二星吸积更多的质量)会受到阻碍。反过来，如果小双星比第三体轻，标准的微分吸积情景就会增强。我们在高温超导中发现的特殊的微分吸积机制有望影响它们的质量比分布。
Young multiple systems accrete most of their final mass in the first few Myr of their lifetime, during the protostellar and protoplanetary phases. Previous studies showed that in binary systems the majority of the accreted mass falls on to the lighter star, thus evolving to mass equalization. However, young stellar systems often comprise more than two stars, which are expected to be in hierarchical configurations. Despite its astrophysical relevance, differential accretion in hierarchical systems remains to be understood. In this work, we investigate whether the accretion trends expected in binaries are valid for higher order multiples. We performed a set of three-dimensional smoothed particle hydrodynamics simulations of binaries and of hierarchical triples (HTs) embedded in an accretion disc, with the code phantom. We identify for the first time accretion trends in HTs and their deviations compared to binaries. These deviations, due to the interaction of the small binary with the infalling material from the circumtriple disc, can be described with a semi-analytical prescription. Generally, the smaller binary of an HT accretes more mass than a single star of the same mass as the smaller binary. We found that in an HT, if the small binary is heavier than the third body, the standard differential accretion scenario (whereby the secondary accretes more of the mass) is hampered. Reciprocally, if the small binary is lighter than the third body, the standard differential accretion scenario is enhanced. The peculiar differential accretion mechanism we find in HTs is expected to affect their mass ratio distribution.