H.E.S.S.大质量星团观测

On the formation of exotic, massive, stellar-remnant black holes at solar and sub-solar metallicities through evolution of massive binaries

The recent inference of a 70M_sun black hole (BH) in the Galactic, detached binary LB-1 has sparked cross-disciplinary debate since a stellar remnant of such large mass is well above what can be expected from stellar-evolutionary theory, especially in an enriched environment like that of the Milky Way. This study focusses on the possibilities of formation of extraordinarily massive BHs at solar and globular cluster (GC)-like metallicities via evolution of massive stellar binaries. A population-synthesis approach is followed utilizing the recently updated BSE program. BHs in the mass range of 5…

旋转的极高质量恒星核心坍缩形成黑洞和大质量盘作为引力波源

Collapse of rotating very massive stellar cores leading to a black hole and a massive disk as a source of gravitational waves

本文研究旋转极高质量恒星核心的坍缩，发现其可形成黑洞与大质量盘，并预测其产生的引力波可被爱因斯坦望远镜探测，为中等质量黑洞形成提供线索。

Stellar-mass black holes in young massive and open stellar clusters IV: updated stellar-evolutionary and black hole spin models and comparisons with the LIGO-Virgo O1/O2 merger-event data

I present a set of long-term, direct, relativistic many-body computations of model dense stellar clusters with up-to-date stellar-evolutionary, supernova (SN), and remnant natal-kick models, including pair instability and pulsation pair instability supernova (PSN and PPSN), using an updated version of NBODY7 N-body simulation program. The N-body model also includes stellar evolution-based natal spins of BHs and treatments of binary black hole (BBH) mergers based on numerical relativity. These, for the first time in a direct N-body simulation, allow for second-generation BBH mergers. The set of…

来自大质量年轻恒星天体的风的相互作用

The interactions of winds from massive young stellar objects

大质量的年轻恒星物体所拥有的超音速恒星风和盘风，当它们与预先存在的双极空腔（由早期喷流活动产生）碰撞时，会产生激波。激波加热的气体发出的热X射线可以被钱德拉X射线天文台等星载天文台观测到。流体动力学模型用于探讨风腔相互作用。对模拟输出进行辐射转移计算，以产生合成X射线观测结果，从而通过与观测结果的比较对模型参数进行约束。该模型揭示了流入和流出物质之间复杂的相互作用，并成功地再现了从大质量年轻恒星物体中观察到的X射线计数率。

Bonn Optimized Stellar Tracks (BoOST). Simulated Populations of Massive and Very Massive Stars for Astrophysical Applications

Massive and very massive stars can play important roles in stellar populations by ejecting strong stellar winds and exploding in energetic phenomena. It is therefore imperative that their behavior be properly accounted for in synthetic model populations. We present nine grids of stellar evolutionary model sequences, together with finely resolved interpolated sequences and synthetic populations, of stars with 9-500 Msun and with metallicities ranging from Galactic metallicity down to 1/250 Zsun. The stellar models were computed with the Bonn evolutionary code with consistent physical ingredient…

Massive Stellar Triples Leading to Sequential Binary Black-Hole Mergers in the Field

Stellar triples with massive stellar components are common, and can lead to sequential binary black-hole mergers. Here, we outline the evolution towards these sequential mergers, and explore these events in the context of gravitational-wave astronomy and the pair-instability mass gap. We find that binary black-hole mergers in the pair-instability mass gap can be of triple origin and therefore are not exclusively formed in dense dynamical environments. We discuss the sequential merger scenario in the context of the most massive gravitational-wave sources detected to date: GW170729 and GW190521.…

The Ecology of the Galactic Centre: Nuclear Stellar Clusters and Supermassive Black Holes

Supermassive black holes are found in most galactic nuclei. A large fraction of these nuclei also contain a nuclear stellar cluster surrounding the black hole. Here we consider the idea that the nuclear stellar cluster formed first and that the supermassive black hole grew later. In particular we consider the merger of three stellar clusters to form a nuclear stellar cluster, where some of these clusters contain a single intermediate-mass black hole (IMBH). In the cases where multiple clusters contain IMBHs, we discuss whether the black holes are likely to merge and whether such mergers are li…

由大质量恒星黑洞提供能量的X射线双星

X-ray binaries powered by massive stellar black holes

恒星黑洞的质量目前被认为是在3-20 Msun的范围内，但非常不确定：最近的观测表明至少存在一个质量>20 Msun的黑洞。母星的金属丰度强烈影响残骸的质量，因为只有贫金属恒星的最终质量可以超过~40 Msun，并且预计会直接坍缩成质量>25 Msun的BH。利用N体模拟研究了年轻致密星团中大质量恒星黑洞（MSBH，质量>25 Msun）的形成和演化。我们研究了MSBH对X射线源布居的影响。

银河系中心是否存在中等质量的黑洞：恒星潮汐破坏率的印记

Is there an intermediate massive black hole in the Galactic center: Imprints on the stellar tidal-disruption rate

一个质量为$10^{3-5} M_\odot$的中等质量黑洞（IMBH）可能会落入银河系中心（GC），并与中心的超大质量黑洞形成一个大质量黑洞双星（MBHB），但目前的观测对所有质量和距离范围的限制并不敏感。最近的发现，MBHB可以提高恒星物体的潮汐破裂事件（TDEs）的速率的启发，我们调查的前景，使用恒星破裂率探测的GC IMBH。我们将IMBH的扰动引入到损失锥理论中，计算了GC中的恒星破裂率。我们发现，比$2000 M_\odot$重的IMBH可以明显提高恒星的破裂率。通过比较Sgr A* 的观测结果和恒星碎片的后退模型，我们认为我们银河系的TDE率不应该明显超过$0.002 yr^{-1}$，因此，集中在高质量端的IMBH的参数空间的一小部分已经可以被排除。为了在剩余的参数空间中得到约束，关键是观测确认或拒绝$10^{-4}$和$10^{-2} yr^{-1}$之间的恒星破裂率，我们讨论了可能的策略，使这样的测量。

恒星系统中的大质量黑洞：“静止”吸积和光度

Massive black holes in stellar systems: 'quiescent' accretion and luminosity

只有一小部分的本地星系拥有吸积黑洞，被归类为活动星系核（AGN）。然而，从球状星团到核星团，再到大质量星系，许多恒星系统都有可能存在黑洞。仅仅是黑洞附近恒星的存在就通过演化恒星的质量损失提供了燃料来源。在本文中，我们评估的预期光度的黑洞嵌入在不同大小和性质的恒星系统，跨越大范围的质量。我们模拟了恒星的分布，并通过几何模型推导出中心黑洞的气体量。我们估计光度的黑洞下简单，但物理接地，假设吸积流。最后讨论了局域宇宙中“静止”黑洞的可探测性。

Probing Massive Scalar Fields from a Pulsar in a Stellar Triple System

Pulsar timing observations precisely test general relativity. Recently, the hierarchical triple system PSR J0337+1715 has placed new constraints on the existence of a fifth force from violation in the strong equivalence principle. Many alternative gravity theories exist with massive (pseudo-)scalar fields to explain a variety of phenomena from the accelerating expansion of the universe at large scales to the QCD strong CP problem at small scales. We here develop a generic formalism for the fifth force effect in theories involving massive scalar fields arising from e.g. string theory. With PSR …

年轻大质量和疏散星团中的恒星质量黑洞及其在引力波产生中的作用

Stellar-mass black holes in young massive and open stellar clusters and their role in gravitational-wave generation II

致密星团中的恒星遗迹黑洞（BH）的研究现在是聚光灯下，特别是由于他们的内在能力，形成双黑洞（BBH）通过动态遇到，潜在的合并通过引力波（GW）辐射。在这项工作中，这是一个最近的研究（论文I）的延续，额外的模型的紧凑星团与初始质量$\lesssim10^5M_\odot$，也与原始双星的小部分（$\lesssim10$ %）的长期发展，应用直接N体的方法，假设国家的最先进的恒星风和残余形成处方。这样，一个更广泛的范围内的计算模型比在纸我实现。正如在论文I中，广义相对论BBH合并仍然主要是由束缚在团簇上的三元组介导的，而不是发生在被弹出的BBH之间。事实上，这种在原位BBH合并的数量，每个集群，往往会显着增加引入一个小人口的原始双星。尽管存在大规模的原始双星，合并BBH，特别是在原位的，被发现是专门动态组装，因此将自旋轨道错位。BBH通常会穿过LISA和LIGO的探测波段，这两种仪器都能听到。黑洞的“动态加热”使电子俘获超新星（ECS）中子星（NS）不能有效地进行质量分离和参与交换作用;动态活跃的黑洞也会交换成$\lesssim1$ Gyr内的任何NS双星。这种年轻的大质量和疏散星团有可能对动态BBH合并检测率做出贡献，其程度与更大质量的球状星团类似。

Companion-driven evolution of massive stellar binaries

At least $70\%$ of massive OBA-type stars reside in binary or higher-order systems. The dynamical evolution of these systems can lend insight into the origins of extreme phenomena such as X-ray binaries and gravitational wave sources. In one such dynamical process, the Eccentric Kozai-Lidov (EKL) Mechanism, a third companion star alters the secular evolution of a binary system. For dynamical stability, these triple systems must have a hierarchical configuration. We explore the effects of a distant third companion's gravitational perturbations on a massive binary's orbital configuration before …