RUI: Understanding Black Hole Accretion Across a Range of Luminosities

恒星质量黑洞，即质量仅为太阳几倍的黑洞，是通过落入黑洞的物质发出的光探测到的，天文学家称之为吸积。这些落入的物质被加热到高温，导致其辐射。黑洞吸积是一个非常复杂的过程：不同的黑洞的亮度或光度可能非常不同，而单个黑洞的光度通常随时间变化很大。查尔斯顿学院的一个研究小组将使用数值计算机模拟来研究黑洞的吸积。他们将研究三种不同的吸积机制，在明显不同的光度范围内，使用尖端的模拟，并与合作者合作，将他们的结果与相应光度状态的观测结果直接进行比较。其目标是解决一些长期存在的难题，并将物理解释附加到观测现象上。预计至少有六名本科生将参与该项目，获得接触计算天体物理学前沿研究的绝佳机会。此外，首席研究员将继续在不同的论坛上传播他的研究成果，包括与当地艺术社区的合作、在当地学校的演讲、YouTube视频、教育iPad应用程序和天文学演讲。近年来，在通过数值模拟来理解黑洞吸积方面取得了巨大进展。在过去的十年中，在这样的模拟中加入了辐射冷却和辐射输运，这使得开始与观测进行更紧密的联系和比较成为可能。研究小组将进行三组主要的模拟，每组都针对一个特定的亮度范围。从中等亮度开始，他们将利用最近在广义相对论辐射磁流体动力学代码中添加的多群辐射输运，直接模拟x射线双星的中间光谱状态，包括软光子和硬光子的贡献。在稍高的亮度下，也就是爱丁顿极限的10-20%，他们计划解决长期存在的难题，即为什么在这个范围内的圆盘在自然界中看起来如此稳定。基于强磁场可以稳定这种磁碟的假设，他们计划测试多种磁场配置，并期望其中一些可能导致高磁化和稳定性。最后，他们将扩展他们的模拟，超越爱丁顿极限，考虑超发光x射线源（ULXs）。改变的方面将是，模拟将倾斜，或倾斜，吸积盘的黑洞对称平面。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Stellar-mass black holes, meaning those only a few times more massive than the Sun, are detected via the light given off by matter falling into the black hole, a process that astronomers call accretion. This infalling matter is heated to high temperatures, causing it to radiate. Black hole accretion is a very complicated process: different black holes can have very different brightness, or luminosity, and the luminosity of an individual black hole usually varies considerably with time. A research group at the College of Charleston will study black hole accretion using numerical computer simulations. They will study three different accretion regimes, in distinctly different luminosity ranges, using cutting-edge simulations, and working with collaborators to compare their results directly with observations of the corresponding luminosity states. The goal is to solve some long-standing puzzles and attach physical explanations to observational phenomena. The expectation is that at least six undergraduate students will be involved in the project, gaining an exceptional opportunity to be exposed to forefront research in computational astrophysics. Additionally, the principal investigator will continue to disseminate his research results in a number of diverse forums, including engagements with the local arts community, presentations in local schools, YouTube videos, educational iPad apps, and Astronomy on Tap presentations.Tremendous progress has been made in recent years in understanding black hole accretion through numerical simulations. The addition of radiative cooling and radiation transport to such simulations over the past decade has made it possible to begin to make tighter connections and comparisons with observations. The research team will conduct three main sets of simulations, each targeting a specific luminosity range. Beginning at moderate luminosities, they will leverage the recent addition of multi-group radiation transport to their general relativistic radiation magnetohydrodynamics code to directly model the intermediate spectral states of X-ray binaries, including both the soft and hard photon contributions. At slightly higher luminosities, 10-20% of the Eddington limit, they plan to tackle the long-standing puzzle as to why disks in this range appear so stable in nature. Working from the hypothesis that strong magnetic fields may stabilize such disks, they plan to test multiple magnetic field configurations with the expectation that some may lead to high magnetization and stability. Lastly, they will extend their simulations beyond the Eddington limit to consider ultra-luminous X-ray sources (ULXs). The transformative aspect will be that the simulations will tilt, or incline, the accretion disk out of the black hole symmetry plane.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.