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
A. Ratheesh, F. Tombesi, K. Fukumura, P. Soffitta, E. Costa, D. Kazanas
Summary: The study investigated the origin and geometry of the accretion disc wind in GRS 1915+105 using high-resolution spectroscopy, revealing a possible magnetic origin of the wind and a multiple ionisation component. The observed variability in the line flux between soft and hard states is most likely due to a large increase in the wind density, suggesting an intimate link between accretion and ejection processes in black hole binaries.
ASTRONOMY & ASTROPHYSICS
(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
Angelo Ricarte, Richard Qiu, Ramesh Narayan
Summary: Using GRMHD simulations, the study explores the impact of magnetic field geometry on circular polarization images of black hole accretion flows, revealing the stability of circular polarization signs and direct properties of the magnetic field. By decomposing images and identifying light bending effects, novel aspects of helical magnetic field structure on circular polarization images are illustrated.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
G. Marcel, J. Ferreira, P-O Petrucci, S. Barnier, J. Malzac, A. Marino, M. Coriat, M. Clavel, C. Reynolds, J. Neilsen, R. Belmont, S. Corbel
Summary: This paper investigates the spectral evolution and radiative efficiency of transient X-ray binaries. The results show that within the JED-SAD model, a unique pattern in the (in)-R-J plane is followed by all cycles. The study also reveals that the accretion flow in the hard states is always radiatively efficient.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
A. Raj, C. J. Nixon
Summary: Accretion disks around black holes can become warped and unstable, leading to a dynamic and variable accretion flow. Recent studies have shown that strongly warped disks may break into discrete rings, causing observable fluctuations in the accretion process.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Indu K. Dihingia, Bhargav Vaidya, Christian Fendt
Summary: Relativistic jets and disc-winds in black hole X-ray binaries and active galactic nuclei are driven by magnetic field mechanisms. Simulation results show that inner disc truncation and oscillations affect the flaring activities in jet mass flow rates. Models with certain parameters are more prone to plasmoid formation and inner disc oscillations, providing insights into spectral state transition phenomena in BH-XRBs.
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
Hai Yang, Feng Yuan, Tom Kwan, Lixin Dai
Summary: This paper investigates the properties of wind and jet launched from a magnetized super-Eddington accretion flow around a supermassive black hole. The simulation data is analyzed using the 'virtual particle trajectory' approach, and the mass flux, velocity, momentum and energy fluxes of wind and jet are obtained. The results show that the mass flux is higher than previous methods suggest, and the momentum flux of wind is larger than that of jet, indicating that wind likely plays a more important role in AGN feedback. The acceleration mechanism of wind and jet is found to be dominated by Lorentz force rather than radiation force.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Raj, C. J. Nixon, S. Dogan
Summary: Numerical simulations of misaligned disks around a spinning black hole show that thin and highly inclined disks are more susceptible to tearing, lower disk viscosity parameter leads to instability, and growth rates of instability are affected by numerical resolution.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Jesse Weder, Christoph Mordasini, Alexandre Emsenhuber
Summary: This study investigates the evolution of large protoplanetary disc populations under the influence of magnetically driven disc winds, internal and external photoevaporation. The simulations show that both strong magnetic torques and weak magnetic winds are necessary to reproduce observed stellar accretion rates. The study also supports the importance of external photoevaporation in disc evolution and its potential influence on planetary formation.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Etienne Martel, Geoffroy Lesur
Summary: This study uses numerical simulations to propose that some transition discs (TDs) may be influenced by magnetised disc winds, which could explain their fast accretion and long-lived cavities. The simulations show that material in the cavity is accreted at sonic velocities, while the cavity itself rotates at a high speed due to magnetic braking.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Angelo Ricarte, Charles Gammie, Ramesh Narayan, Ben S. Prather
Summary: The Event Horizon Telescope (EHT) collaboration has produced the first resolved images of supermassive black holes. They predict spectral index maps of M87* and Sgr A* and show that the spectral index increases with increasing magnetic field strength, electron temperature, and optical depth. Spectral index maps can be used to discriminate between different models if our understanding of plasma physics improves.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Masaaki Takahashi, Motoki Kino, Hung-Yi Pu
Summary: This study investigates stationary and axisymmetric transmagnetosonic outflows in the magnetosphere of a rotating black hole, focusing on plasma acceleration efficiency and energy conversion. By analyzing parameter dependence and recent observations, the study estimates the positions of key surfaces in the flow and discusses the electromagnetic energy flux from the rotating BH.
Article
Astronomy & Astrophysics
Lev Titarchuk, Elena Seifina
Summary: By analyzing the outburst activity of MAXI J1348-630, we find that its energy spectra in all spectral states can be modeled using a combination of Comptonization and Gaussian iron-line components. We also observe a correlation between the X-ray photon index, Gamma, and the mass accretion rate, M. Furthermore, we provide observational evidence of the presence of a black hole in MAXI J1348-630 based on the behavior of Gamma.
ASTRONOMY & ASTROPHYSICS
(2023)
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
Michail Chabanov, Samuel D. Tootle, Elias R. Most, Luciano Rezzolla
Summary: By conducting high-resolution, global, and high-order general-relativistic magnetohydrodynamic simulations, we examine the effects of a purely crustal magnetic field and a dipolar magnetic field that fills the entire star on binary neutron star mergers. The results show that the crust configuration is highly effective in generating strong magnetic fields during the Kelvin-Helmholtz-instability stage, but fails to achieve the same level of magnetic field amplification as the full-star configuration. This is due to the lack of magnetized material in the neutron-star interiors and the surface losses of highly magnetized matter in the crust configuration. The differences in final magnetic energies between the two configurations exceed one order of magnitude. We briefly discuss the implications of these findings for astrophysical observables and the determination of magnetic topology in merging binaries.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Elias R. Most, Eliot Quataert
Summary: Using numerical simulations, we investigate the possibility of a jet-like outflow from a hypermassive neutron star during the early stages of the merger. We find that buoyant instabilities can lead to periodic emission of electromagnetic flares followed by a collimated outflow, both with quasiperiodic substructure. These early-time outflows may be precursors to short-duration gamma-ray bursts (sGRBs).
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
J. F. Mahlmann, A. A. Philippov, V. Mewes, B. Ripperda, E. R. Most, L. Sironi
Summary: The origins of X-ray outbursts from magnetars are still unknown. There are instabilities in the magnetosphere that can explain the luminosities of these X-ray flares. Crustal surface motions can twist the magnetosphere, resulting in different eruptive dynamics. Additionally, three-dimensional twist models capture the non-axisymmetric dynamics in dipolar magnetospheres.
ASTROPHYSICAL JOURNAL LETTERS
(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
Physics, Multidisciplinary
Carolyn A. Raithel, Elias R. Most
Summary: Gravitational wave detections of binary neutron star inspirals are important for understanding dense matter. However, a new degeneracy in the mapping from tidal deformability data to the equation of state (EOS) arises in models with strong phase transitions.
PHYSICAL REVIEW LETTERS
(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
Elias R. Most, Alexander A. Philippov
Summary: The presence of magnetic fields in the late inspiral of black hole-neutron star binaries can lead to electromagnetic flaring activity, which may result in fast-radio-burst-like transients and X-ray emission.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
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
K. R. Abhishek Hegade, Elias R. Most, Jorge Noronha, Helvi Witek, Nicolas Yunes
Summary: We investigate the formation of scalar monopole and dipole hair in scalar Gauss-Bonnet theory and dynamical Chern-Simons theory. It is found that the spherically symmetric mode of the dipole hair is determined by the mass of the spacetime and the value of the monopole hair. The dynamics of the L1/4 1 mode of the dipole hair is closely related to the appearance of the event horizon during axisymmetric collapse, leading to the radiation of certain modes that could have been divergent in the future of the collapse. Simulations of the gravitational collapse of a rapidly rotating neutron star confirm these predictions.
Article
Astronomy & Astrophysics
Elias R. Most, Anton Motornenko, Jan Steinheimer, Veronica Dexheimer, Matthias Hanauske, Luciano Rezzolla, Horst Stoecker
Summary: Binary neutron-star mergers and heavy-ion collisions are connected through the nuclear matter formed during these extreme events. This study compares the conditions in both systems through their geometry and thermodynamics. The results show that low-energy heavy-ion collisions can reproduce states of matter similar to those in binary neutron-star mergers.
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)