Article
Astronomy & Astrophysics
A. Jimenez-Rosales, J. Dexter, S. M. Ressler, A. Tchekhovskoy, M. Baubock, Y. Dallilar, P. T. de Zeeuw, A. Drescher, F. Eisenhauer, S. von Fellenberg, F. Gao, R. Genzel, S. Gillessen, M. Habibi, T. Ott, J. Stadler, O. Straub, F. Widmann
Summary: Through simulations of accreting black holes, it is found that subtracting linear polarization can enhance the photon ring feature, leading to precise measurements of black hole mass and spin.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Thomas Bronzwaer, Jordy Davelaar, Ziri Younsi, Monika Moscibrodzka, Hector Olivares, Yosuke Mizuno, Jesse Vos, Heino Falcke
Summary: Accreting black holes often display a dark central region called the black hole shadow, conveying information about the black hole's mass and spin. The observed central brightness depression, or image shadow, can differ from the black hole shadow due to factors such as evacuation of the innermost region of the accretion flow and obscuration by optically thick regions. The study found that a compact and optically thin emission region allows for measurement of the black hole shadow size with an accuracy of 5%, indicating that certain conditions must be met for accurate measurements.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Ramesh Narayan, Andrew Chael, Koushik Chatterjee, Angelo Ricarte, Brandon Curd
Summary: We present the results of nine simulations of radiatively inefficient magnetically arrested discs (MADs) with different black hole spin parameters. Our study finds that the saturated magnetic flux level and jet power of MAD discs strongly depend on the black hole spin. Prograde discs have higher magnetic flux and more powerful jets compared to retrograde discs. Moreover, MADs with spinning black holes launch jets with generalized parabolic profiles, and the width of the jets varies with distance from the black hole according to a power-law function. We also observe a strong correlation between the disc-jet geometry and the dimensionless magnetic flux, with prograde systems displaying thinner equatorial accretion flows near the black hole and wider jets compared to retrograde systems. Additionally, we find different trends in disc variability between prograde and retrograde MADs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Samik Mitra, Debaprasad Maity, Indu Kalpa Dihingia, Santabrata Das
Summary: We present a novel approach to study the global structure of steady, axisymmetric, advective, magnetohydrodynamic (MHD) accretion flow around black holes in full general relativity (GR). Considering ideal MHD conditions and relativistic equation of state (REoS), we solve the governing equations to obtain all possible smooth global accretion solutions. We examine the dynamical and thermodynamical properties of accreting matter in terms of the flow parameters, namely energy (epsilon), angular momentum (L), and local magnetic fields. We observe that toroidal component of the magnetic fields generally dominates over radial component at the disc equatorial plane, suggesting the importance of toroidal magnetic field in regulating the disc dynamics. The disc remains mostly gas pressure dominated except at the near horizon region where magnetic fields become indispensable. We calculate the viscosity parameter and examine the scaling relation between alpha and beta, distinguishing two domains along the radial extent of the disc. We discuss the utility of the present formalism in GRMHD simulation studies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Brandon Curd
Summary: The study simulated accretion disc formation resulting from tidal disruption of a solar mass star around a supermassive black hole using KORAL code. The rate of circularization of the disc is faster for pericenter radii closer to the black hole, with mildly super-Eddington radiation and highly asymmetric photosphere. The simulations suggest tidal disruption events should be radiatively inefficient.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
J. Podgorny, M. Dovciak, F. Marin, R. Goosmann, A. Rozanska
Summary: X-ray polarimetric missions planned for this decade will provide new means to study inner accretion flow in compact accreting sources. This study presents a missing piece in the global polarization models of black hole accretion discs by computing the reflected X-ray emission from the disc and obtaining detailed spectral and polarization properties.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. M. Velasquez-Cadavid, Fabio D. Lora-Clavijo, Oscar M. Pimentel, J. A. Arrieta-Villamizar
Summary: Magnetic fields in black hole accretion discs affect the physical properties of the medium and have implications on the radiation emitted. Observations can be used to determine the magnetic properties of the material and understand the properties of space-time.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Brandon Curd, Razieh Emami, Richard Anantua, Daniel Palumbo, Sheperd Doeleman, Ramesh Narayan
Summary: We present general relativistic radiation magnetohydrodynamics (GRRMHD) simulations of super-Eddington accretion flows around supermassive black holes (SMBHs), which may apply to tidal disruption events (TDEs). Gas flowing beyond the funnel wall expands conically and drives a strong shock at the jet head while variable mass ejection and recollimation, along the jet axis, results in internal shocks and dissipation. The emission is extremely sensitive to T-i/T-e as some models show an order-of-magnitude decrease in the peak frequency and up to four orders-of-magnitude decline in their radio/submillimetre luminosity as T-i/T-e approaches 20.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Roberta Duarte, Rodrigo Nemmen, Joao Paulo Navarro
Summary: The study found that deep neural networks trained on simulation data can effectively learn the distribution of black hole accretion flows and evolve quickly. However, the model may drift from ground truth and suffer from mass continuity issues after a long duration, as well as exhibit challenges in generalizing to simulations with different initial conditions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. Podgorny, M. Dovciak, R. Goosmann, F. Marin, G. Matt, A. Rozanska, V Karas
Summary: The rebirth of X-ray polarimetric instruments will have a significant impact on our understanding of compact accreting sources. This study provides a numerical estimate of X-rays in the lamp-post coronal model, including the polarized reflected radiation from the accretion disc. The results show that relativistic disc reflection remains important for the interpretation of X-ray polarimetric observations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Brandon Curd, Ramesh Narayan
Summary: In this study, we used simulations to investigate magnetically arrested discs (MADs) around non-spinning and spinning supermassive black holes (BHs). We found that spinning BHs produce stronger jets and are able to extract more energy from the BH compared to non-spinning BHs. The power of the jets decreases with decreasing accretion rate, while the total and radiative efficiencies increase.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
O. Porth, Y. Mizuno, Z. Younsi, C. M. Fromm
Summary: Based on 3D general relativistic magnetohydrodynamic simulations, this study examines a model for magnetic flux eruptions from the black hole magnetosphere. The results suggest that the erupted flux bundles can power infrared and X-ray flares, and the motion within the magnetically supported flow is significantly sub-Keplerian.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Richard Qiu, Angelo Ricarte, Ramesh Narayan, George N. Wong, Andrew Chael, Daniel Palumbo
Summary: Researchers have introduced a new library consisting of 535,194 model images of supermassive black holes and Event Horizon Telescope (EHT) targets Sgr A* and M87*. They used general relativistic radiative transfer calculations and general relativistic magnetohydrodynamics simulations to compute these images. They then trained a random forest machine learning model on various polarimetric observables to infer underlying black hole and accretion flow parameters.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Bidisha Bandyopadhyay, Christian Fendt, Dominik R. G. Schleicher, Christos Vourellis
Summary: This study uses numerical simulations and ray-tracing to investigate the appearance features and formation models of black hole environments, confirming that ring-like features can be consistent with observations, and noting that other SMBHs may show additional features like winds and jets in the observations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Elliot M. Lynch, Gordon Ogilvie
Summary: Current research suggests that whether tidal disruption events circularize or accrete directly as a highly eccentric disc depends sensitively on the disc thermodynamics; a coherent magnetic field has a stabilizing effect on the dynamics and can significantly alter the behavior of highly eccentric radiation-dominated discs; magnetic fields play an important role in the evolution of TDE discs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jeffrey A. Hodgson, Bindu Rani, Junghwan Oh, Alan Marscher, Svetlana Jorstad, Yosuke Mizuno, Jongho Park, S. S. Lee, Sascha Trippe, Florent Mertens
Summary: The study reveals a connection between 3C 84 and gamma-ray emission, mainly generated in high-energy radiation through kinematic changes in the jet. The radio structure indicates that the jet once moved at extreme speeds and reached maximum velocity in a relatively short period of time. The research also suggests the presence of multiple high-energy radiation sites within the source.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Leonid I. Gurvits, Zsolt Paragi, Viviana Casasola, John Conway, Jordy Davelaar, Heino Falcke, Rob Fender, Sandor Frey, Christian M. Fromm, Cristina Garcia Miro, Michael A. Garrett, Marcello Giroletti, Ciriaco Goddi, Jose-Luis Gomez, Jeffrey van der Gucht, Jose Carlos Guirado, Zoltan Haiman, Frank Helmich, Elizabeth Humphreys, Violette Impellizzeri, Michael Kramer, Michael Lindqvist, Hendrik Linz, Elisabetta Liuzzo, Andrei P. Lobanov, Yosuke Mizuno, Luciano Rezzolla, Freek Roelofs, Eduardo Ros, Kazi L. J. Rygl, Tuomas Savolainen, Karl Schuster, Tiziana Venturi, Martina C. Wiedner, J. Anton Zensus
Summary: THEZA is a concept proposed in the ESA Voyage 2050 White Paper for ultra-sharp imaging of celestial radio sources, focusing on physics of spacetime near supermassive black holes. It aims to provide researchers with orders of magnitude improvements in resolution and dynamic range for direct imaging studies, opening up a range of previously unreachable parameters of observational astrophysics.
EXPERIMENTAL ASTRONOMY
(2021)
Article
Astronomy & Astrophysics
S. Cielo, O. Porth, L. Iapichino, A. Karmakar, H. Olivares, C. Xia
Summary: In this paper, we present our experience with modernizing the GR-MHD code BHAC and improving its hybrid parallelization scheme. We use performance profiling tools to guide the optimization of the OpenMP parallel regions. By assessing scaling and communication patterns, we address MPI bottlenecks and achieve a 28% improvement in performance. We also test the portability of these optimizations to different hardware architectures.
ASTRONOMY AND COMPUTING
(2022)
Article
Astronomy & Astrophysics
Alejandro Cruz-Osorio, Christian M. Fromm, Yosuke Mizuno, Antonios Nathanail, Ziri Younsi, Oliver Porth, Jordy Davelaar, Heino Falcke, Michael Kramer, Luciano Rezzolla
Summary: M87 has been the target of numerous astronomical observations and the origin of its jets, driven by black holes, remains unclear. Current understanding suggests that the spin of the black hole and magnetic fields play crucial roles in jet formation. Simulations and calculations have provided rough constraints on the dimensionless spin of the black hole in M87.
Review
Astronomy & Astrophysics
Yosuke Mizuno
Summary: Relativistic jets are collimated plasma outflows with relativistic speeds that are typically associated with compact objects like black holes, mainly produced through magnetohydrodynamic processes. Over the past few decades, general relativistic MHD codes have been developed and successfully applied to simulate and observe the formation of relativistic jets, providing valuable insights into their origin and behavior.
Article
Astronomy & Astrophysics
Nibedita Kalita, Yuhai Yuan, Minfeng Gu, Junhui Fan, Yosuke Mizuno, Peng Jiang, Alok C. Gupta, Hongyan Zhou, Xiang Pan, Anton A. Strigachev, Rumen S. Bachev, Lang Cui
Summary: BL Lacertae underwent a series of historical high flux activity from August 2020 to November 2021, spanning the optical to VHE gamma-rays. The first historical maxima outburst event during October-November in the g, r, and i bands was observed using the 1.26 m telescope at the Xinglong Observatory, China. Intranight variations with amplitude up to 30% and a few tens of minutes variability timescale were detected, indicating the presence of jet mini-structures.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Jie-Shuang Wang, Brian Reville, Yosuke Mizuno, Frank M. Rieger, Felix A. Aharonian
Summary: X-ray observations of kiloparsec-scale extragalactic jets indicate a synchrotron origin and the short cooling times of emitting electrons require a distributed electron acceleration. In this study, 3D relativistic magnetohydrodynamic simulations are performed to investigate the formation of a spine-sheath structure and turbulence development in a relativistic jet propagating into a static cocoon. The results show that a sheath is generated on the interface of the spine and the cocoon due to the Kelvin-Helmholtz instability, and turbulence develops with Kolmogorov scaling in both the spine and the sheath.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Andrew Chael, Sara Issaoun, Dominic W. Pesce, Michael D. Johnson, Angelo Ricarte, Christian M. Fromm, Yosuke Mizuno
Summary: The Event Horizon Telescope has produced high-resolution images of plasma flow around supermassive black holes in Sgr A* and M87* using advanced imaging technology. The next-generation Event Horizon Telescope will significantly improve observation data with multiple frequency bands. Simultaneous reconstruction of interferometric images at multiple frequencies along with their spectral index maps produces higher-quality and more scientifically useful results than independent image reconstructions at each frequency.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Hong-Xuan Jiang, Yosuke Mizuno, Christian M. Fromm, Antonios Nathanail
Summary: We conducted two-dimensional two-temperature general relativistic magnetohydrodynamic simulations to study magnetized accretion flows from tori with different sizes and magnetic loop polarities. Our simulations revealed that the accretion process strongly depends on the size of the magnetic loops, with small loops not reaching the magnetically arrested regime. The formation of plasmoids, which play a crucial role in electron heating, is strongly influenced by the size of the magnetic loops and the occurrence of magnetic reconnection. The properties of plasmoid formation in different magnetic field configurations provide new insights into flaring activity and electron thermodynamics in Sagittarius A*.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Optics
Guangtao Zhu, Tomoya Miyamae, Kohei Noda, Heeyoung Lee, Kentaro Nakamura, Yosuke Mizuno
Summary: This paper proposes a newly configured optical correlation-domain reflectometry (OCDR) without the use of an electrical spectrum analyzer (ESA) for high-speed distributed reflectivity measurement with an enhanced spatial resolution. The operation and potential of ESA-free OCDR are analyzed by numerical simulation and verified by comparison experiments. The experimental results show that the ESA-free OCDR can achieve improved spatial resolution at higher operation speeds.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Astronomy & Astrophysics
Fumie Tazaki, Yuzhu Cui, Kazuhiro Hada, Motoki Kino, Ilje Cho, Guang-Yao Zhao, Kazunori Akiyama, Yosuke Mizuno, Hyunwook Ro, Mareki Honma, Ru-Sen Lu, Zhi-Qiang Shen, Lang Cui, Yoshinori Yonekura
Summary: By using the regularized maximum likelihood (RML) method, we reconstructed high-resolution images of the M87 22 GHz data observed with the East Asian VLBI Network (EAVN). Compared to the conventional imaging method CLEAN, the RML images showed a brighter core and a jet extending about 30 mas to the northwest with higher resolution. The study provides an important advancement for future observations of the EAVN to investigate the detailed structure and time variability of the jet.
Article
Astronomy & Astrophysics
Prashant Kocherlakota, Ramesh Narayan, Koushik Chatterjee, Alejandro Cruz-Osorio, Yosuke Mizuno
Summary: This article discusses the importance of using horizon-penetrating coordinates in general relativity to simulate the accretion of magnetized gas on compact astrophysical objects. These simulations provide insights into the physics of accretion flows and jets near the event horizon of black holes and have implications for interpreting recent Event Horizon Telescope images.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Indu K. Dihingia, Yosuke Mizuno, Prateek Sharma
Summary: Researchers used general relativistic magnetohydrodynamic simulations to study the decaying phase of outbursts in black hole X-ray binaries, finding different phases and observing quasiperiodic oscillations.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
H. Olivares, I. M. Peshkov, E. R. Most, F. M. Guercilena, L. J. Papenfort
Summary: This article presents a formulation of the Einstein equations that is similar to relativistic magnetohydrodynamics and electrodynamics in material media. This formulation is suitable for a wide range of applications, computationally efficient, and can be used to simulate astrophysical systems.
