The dependence of the final fate of supermassive star (SMS) cores on their mass and angular momentum is studied with simple modeling. SMS cores in the hydrogen burning phase encounter the general relativistic instability during the stellar evolution if the mass is larger than $\sim 3 \times 10^4M_\odot$. Spherical SMS cores in the helium burning phase encounter the general relativistic instability prior to the onset of the electron-positron pair instability if the mass is larger than $\sim 1\times 10^4M_\odot$. For rapidly rotating SMS cores, these values for the threshold mass are enhanced by up to a factor of $\sim 5$, and thus, for SMSs with mass smaller than $\sim 10^4M_\odot$ the collapse is triggered by the pair-instability, irrespective of the rotation. After the onset of the general relativistic instability, SMS cores in the hydrogen burning phase with reasonable metallicity are likely to collapse to a black hole irrespective of the degree of rotation, whereas the SMS cores in the helium burning phase could explode via nuclear burning with no black hole formation, as previous works demonstrate.
Observed supermassive black holes in the early universe have several proposed formation channels, in part because most of these channels are difficult to probe. One of the more promising channels, the direct collapse of a supermassive star, has several possible probes including the explosion of a helium-core supermassive star triggered by a general relativistic instability. We develop a straightforward method for evaluating the general relativistic radial instability without simplifying assumptions and apply it to population III supermassive stars taken from a post Newtonian stellar evolution …
Supermassive stars (SMSs) collapsing via the general-relativistic (GR) instability are invoked as the possible progenitors of supermassive black holes. Their mass and angular momentum at the onset of the instability are key in many respects, in particular regarding the possibility for observational signatures of direct collapse. Here, we study the stability of rotating, rapidly accreting SMSs against GR and derive the properties of these stars at death. On the basis of hylotropic structures, relevant for rapidly accreting SMSs, we define rotation profiles under the assumption of local angular …
Theoretical models show that the power of relativistic jets of active galactic nuclei depends on the spin and mass of the central supermassive black holes, as well as the accretion. Here we report an analysis of archival observations of a sample of blazars. We find a significant correlation between jet kinetic power and the spin of supermassive black holes. At the same time, we use multiple linear regression to analyze the relationship between jet kinetic power and accretion, spin and black hole mass. We find that the spin of supermassive black holes and accretion are the most important contri…
The origin of high-redshift quasars and their supermassive black hole engines is unclear. One promising solution is the collapse of a primordial supermassive star. Observational confirmation of this scenario may be challenging, but a general relativistic instability supernova provides one avenue for such. Previous studies have found that a general relativistic instability supernova has a potentially decades-long plateau phase visible to JWST at high redshift. In this work, we examine stars with mass just below the general relativistic instability supernova mass range. These stars pulsate, ejec…
The formation of supermassive black holes by direct collapse would imply the existence of supermassive stars (SMSs) and their collapse through the general-relativistic (GR) instability into massive black hole seeds. However, the final mass of SMSs is weakly constrained by existing models, in spite of the importance this quantity plays in the consistency of the direct collapse scenario. We estimate the final masses of spherical SMSs in the whole parameter space relevant for these objects. We build analytical stellar structures (hylotropes) that mimic existing numerical SMS models accounting for…
Timing a pulsar in a close orbit around the supermassive black hole SgrA* at the center of the Milky Way would open the window for an accurate determination of the black hole parameters and for new tests of General Relativity and alternative modified gravity theories. An important relativistic effect which has to be taken into account in the timing model is the propagation delay of the pulses in the gravitational field of the black hole. Due to the extreme mass ratio of the pulsar and the supermassive back hole we use the test particle limit to derive an exact analytical formula for the propag…
We present the expected observational properties of a general relativistic instability supernova (GRSN) from the 55,500 Msun primordial (Population III) star. Supermassive stars exceeding 1e4 Msun may exist in the early Universe. They are generally considered to collapse through the general relativistic instability to be seed black holes to form supermassive (~ 1e9 Msun) black holes observed as high-redshift quasars. Some of them, however, may explode as GRSNe if the explosive helium burning unbinds the supermassive stars following the collapse triggered by the general relativistic instability…
Dark matter mounds from the collapse of supermassive stars: a general-relativistic analysis
Scuola Internazionale Superiore di Studi Avanzati (SISSA)（高等高级研究国际学院）；Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）；University of Amsterdam（阿姆斯特丹大学）；Institute for Fundamental Physics of the Universe (IFPU)（宇宙基础物理研究所）；Instituto de Fisica de Cantabria (CSIC-UC)（坎塔布里亚物理研究所）；INFN Sezione di Pisa（意大利国家核物理研究所比萨分部）
Constraining spins of supermassive black holes from TeV variability. II. fully general relativistic calculations
观测到了来自M87中心的TeV能量光子的快速变化，为估算超大质量黑洞（SMBH）的自旋提供了新的线索.我们扩展了Wang et al.（2008）的研究，包括所有的广义相对论效应。通过数值求解辐射无效吸积流的相对论流体动力学方程组，得到了黑洞周围的辐射场。在Kerr度规中计算了TeV光子对产生的辐射场的光学深度。我们发现，光学深度强烈依赖于：（1）吸积率为$\tautev\propto \dot{M}^{2.5-5.0}$;（2）黑洞自旋;（3）TeV源的位置。结合光学厚度和RIAF辐射的光谱能量分布，可以大大缓解RIAF模型中自旋与其他自由参数的强烈退化。我们将这个模型应用到M87中，发现黑洞的最小比角动量为$a\sim0.8$。本方法适用于M87类源与未来的TeV的排放量的检测，以限制SMBHs的自旋。
Electron-positron cascade in magnetospheres of supermassive Kerr black holes and the origin of relativistic AGN jets
University of Kansas（堪萨斯大学）；Massachusetts Institute of Technology（麻省理工学院）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文中心）
Supermassive black holes might form by direct collapse, with a supermassive star (SMS) as progenitor. In this scenario, the SMS accretes at > 0.1 Msun/yr until it collapses into a massive black hole seed due to the general-relativistic (GR) instability. However, the exact mass at which the collapse occurs is not known, as existing numerical simulations give divergent results. Here, this problem is addressed analytically, which allows for ab initio, reliable determination of the onset point of the GR instability, for given hydrostatic structures. We apply the relativistic equation of radial pul…
Transient Relativistic Iron Emission Line from an X-ray Flaring Supermassive Black Hole
California Institute of Technology（加州理工学院）；University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；Clemson University（克莱姆森大学）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Università di Bologna（博洛尼亚大学）；INAF, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）
In this paper, we describe the results of three-dimensional relativistic magnetohydrodynamic simulations aimed at probing the role of regular magnetic field on the development of the instability that accompanies recollimation of relativistic jets. In particular, we studied the recollimation driven by the reconfinement of jets from active galactic nuclei (AGN) by the thermal pressure of galactic coronas. We find that a relatively weak azimuthal magnetic field can completely suppress the recollimation instability in such jets, with the critical magnetisation parameter $σ_{cr} < 0.01$. We argue t…
Line shifts in accretion disks - the case of Fe K$α$
在这里，我们提出了一个简短的概述和主要结果，我们的调查的几种影响，可以诱导移动广泛的Fe K $α$线发射的相对论性吸积盘周围的单一和二元超大质量黑洞。我们采用基于Kerr度规的射线追踪方法，通过数值模拟研究了经典多普勒频移、狭义相对论横向多普勒频移和多普勒波束效应、广义相对论引力红移以及盘发射率的扰动在观测到的Fe K $α$谱线轮廓形成中的作用。此外，我们还研究了超大质量黑洞双星系统动力学引起的多普勒频移是否会对观测到的谱线轮廓产生影响。结果表明，所有这些效应对单黑洞和双超大质量黑洞周围相对论性吸积盘发射的宽Fe K $α$线的观测轮廓都有显著的影响.
Discovery of minute-scale polarization angle rotation in a supermassive black hole jet
University of Crete（克里特大学）；Foundation for Research and Technology-Hellas（希腊研究与技术基金会）；The Pennsylvania State University（宾夕法尼亚州立大学）；Institute of Astrobiology, University of Crete（克里特大学天体生物学研究所）；Chalmers University of Technology（查尔姆斯理工大学）；Friedrich-Alexander Universität Erlangen-Nürnberg（埃尔朗根-纽伦堡弗里德里希·亚历山大大学）
GRRMHD Simulations of Tidal Disruption Event Accretion Disks around Supermassive Black Holes: Jet Formation, Spectra, and Detectability
利用广义相对论辐射MHD（GRRMHD）模拟了由潮汐扰动事件（TDE）形成的超爱丁顿黑洞（BH）吸积盘。我们考虑基准的情况下，太阳质量的恒星在一个温和的穿透轨道被一个超大质量BH的质量$10^6 \, M_\odot$破坏，并考虑峰值回落率的时代。我们对模拟数据进行后处理以计算视角相关光谱。我们进行了一个参数的研究作为BH自旋和磁通量的函数的吸积盘的动力学，并计算模型光谱作为观察者的视角的函数。我们还考虑基于模型光谱的检测限。我们发现，一个吸积盘与一个相对较弱的磁场周围的BH（所谓的SANE制度的吸积）不发射相对论性喷流，无论BH是旋转。这种模式合理地再现了非喷流TDE的几个观测特性。对于具有强磁场（MAD区域）的非旋转BH也是如此。我们的一个模拟有一个快速旋转的BH（自旋参数0.9）以及一个MAD吸积盘。这个模型发射了一个强大的相对论性喷流，它是由BH自旋能量驱动的。它令人惊讶地再现了喷射的TDE Swift J1644+57的高能量发射和喷射结构。因此，喷射TDE可能对应于具有快速旋转BH和MAD吸积的TDE系统的子集。
We investigate the possibility of a supernova in supermassive ($5 \times 10^4 \;M_\odot$) population III stars induced by a general relativistic instability occurring in the helium burning phase. This explosion could occur via rapid helium burning during an early contraction of the isentropic core. Such an explosion would be visible to future telescopes and could disrupt the proposed direct collapse formation channel for early universe supermassive black holes. We simulate first the stellar evolution from hydrogen burning using a 1D stellar evolution code with a post Newtonian approximation; a…
