Imaging the event horizon of M87* from space on different timescales
Radboud University（拉德堡德大学）；Pontificia Universidad Católica de Chile（智利天主教公立大学）；Harvard University（哈佛大学）；Flatiron Institute（平顿研究所）；Columbia University（哥伦比亚大学）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；ASTRON, The Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）
Anastasia Shlentsova, Freek Roelofs, Sara Issaoun, Jordy Davelaar, Heino Falcke
备注：
20 pages, 23 figures, accepted for publication in A&A
The concept of a new space very long baseline interferometry system named the Event Horizon Imager (EHI) has been proposed to dramatically improve black hole imaging and provide precise tests of the theory of general relativity. We investigate the ability to make high-resolution movies of the black hole shadow and jet launching region around the supermassive black hole M87* and other black hole jets with a three-satellite EHI configuration. We aim to identify orbital configurations to optimize the uv-coverage to image variable sources. Observations of general relativistic magnetohydrodynamics models were simulated for the configuration, consisting of three satellites in circular medium earth orbits with an orbital plane perpendicular to the line of sight. The expected noise was based on preliminary system parameters. Movie frames, for which a part of the uv-coverage may be excessively sparse, were reconstructed with algorithms that recover missing information from other frames. Averaging visibilities accumulated over multiple epochs of observations with an appropriate orbital configuration then improves the image quality. With an enhanced signal-to-noise ratio (S/N), timescales of observed variability were decreased. Our simulations show that the EHI with standard system parameters is capable of imaging the variability in the M87* environment on event horizon scales with approximately a month-long temporal resolution. The EHI with more optimistic noise parameters (enhancing S/N about 100-fold) would allow for imaging of the variability on gravitational timescales. Observations with an EHI setup at lower frequencies are capable of imaging the variability in extended jets. The EHI concept can be used to image the variability in a black hole environment and extended jets, allowing for stronger tests of gravity theories and models of black hole accretion, plasma dynamics, and jet launching.
Expanding the Horizon of Black Hole Imaging with AtLAST
Heriot-Watt University（赫瑞-瓦特大学）；University of Naples Federico II（那不勒斯费德里科二世大学）；MSSL, University College London（伦敦大学学院太空与气候物理研究所）；Yamaguchi University（山口大学）；Academia Sinica Institute of Astronomy and Astrophysics（中央研究院天文及天文物理研究所）；Nagoya City University（名古屋市立大学）；Massachusetts Institute of Technology Haystack Observatory（麻省理工学院海斯塔克观测站）；Niigata University（新潟大学）；Instituto de Astrofísica de Andalucía, IAA-CSIC（安达卢西亚天体物理研究所）；University of Lancashire（兰开夏大学）
On the universality of the split monopole black hole magnetosphere
Columbia University（哥伦比亚大学）；Anton Pannekoek Institute（安东·潘内克研究所）；Canadian Institute for Theoretical Astrophysics（加拿大理论天体物理研究所）；University of Toronto（多伦多大学）；Perimeter Institute for Theoretical Physics（基础理论物理研究所）；Flatiron Institute（平顿研究所）
VASTER: The ASKAP real-time fast-imaging pipeline -- overview and discovery of two long period transients
Swinburne University of Technology（斯威本科技大学）；The University of Sydney（悉尼大学）；CSIRO Space and Astronomy（澳大利亚联邦科学与工业研究组织空间与天文部）；University of Wisconsin-Milwaukee（威斯康星大学密尔沃基分校）；Curtin University（科廷大学）
Simulations of imaging the event horizon of Sagittarius A* from space
有人提出，亚毫米波的甚长基线干涉测量（VLBI）将使我们能够对银河系中心人马座A *（Sgr A *）黑洞的阴影进行成像，从而验证广义相对论的基本预测。本文介绍了一个新的空间VLBI任务概念的成像模拟。该概念的初步设计研究已作为事件视界成像仪（EHI）提出。EHI可能适用于在高频（高达~690 GHz）下对Sgr A * 进行成像，这与在230 GHz下进行地基VLBI相比具有显著优势。EHI的概念设计包括两个或三个卫星在极地或赤道圆形中地球轨道略有不同的半径。由于卫星沿着各个轨道的相对漂移，这种设置将导致具有长基线（高达~60 G λ）的密集螺旋形紫外线覆盖，从而允许对射电源进行极高分辨率和高保真度成像。我们模拟EHI观测的广义相对论磁流体动力学模型的Sgr A * 和计算预期的噪声的基础上初步的系统参数。在长基线上，信噪比可能很低，如果系统足够相位稳定，并且卫星轨道可以足够精确地重建，则可以检测到条纹。然后，对多个观测时期积累的亮度进行平均可以帮助提高图像质量。有了三颗卫星，闭合阶段可用于成像。我们的模拟表明，EHI可以在几个月的观测时间内以4 μ s（约为阴影直径的8%）的分辨率成像Sgr A * 的黑洞阴影。因此，EHI概念可以用来测量黑洞阴影，比地基VLBI精确得多，允许更强的测试广义相对论和吸积模型。
Searching for Long-Period Radio Transients in ASKAP EMU Data with 10-Second Imaging
The University of Sydney（悉尼大学）；ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)（引力波发现卓越中心）；Australia Telescope National Facility, CSIRO（澳大利亚望远镜国家设施，CSIRO）；Swinburne University of Technology（斯威本科技大学）；Shanghai Astronomical Observatory, CAS（中国科学院上海天文台）；State Key Laboratory of Radio Astronomy and Technology（射电天文与技术国家重点实验室）；CSIRO, Space and Astronomy（CSIRO空间与天文部门）；University of Wisconsin-Milwaukee（威斯康星大学密尔沃基分校）；University of Maryland, College Park（马里兰大学帕克分校）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Center for Research and Exploration in Space Science and Technology, NASA/GSFC（NASA/GSFC空间科学与技术研究探索中心）
Short timescale variation in the submillimeter flux of Sagittarius A*
National Astronomical Observatory of Japan（日本国立天文台）；Japan Meteorological Agency（日本气象厅）；Joint ALMA Observatory（ALMA联合 observatory）；The Graduate University for Advanced Studies (SOKENDAI)（高级研究院 (SOKENDAI)）；Meisei University（明海大学）；The University of Tokyo（东京大学）；Keio University（庆应义塾大学）
