Article
Physics, Particles & Fields
Meirong Tang, Zhaoyi Xu
Summary: The successful observation of the M87 supermassive black hole using the EHT provides an opportunity to study the theory of gravity. In this study, the researchers obtained the exact solution for a rotating short-hair black hole and analyzed the effect of hairs on the black hole shadow. The results show that the rotation and scalar hairs have significant influences on the shape of the black hole shadow.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Astronomy & Astrophysics
Dimitrios Psaltis, Colm Talbot, Ethan Payne, Ilya Mandel
Summary: This paper quantifies the potential upper bounds on black-hole metric deviations based on observations of black-hole shadows and binary black-hole inspirals. The study finds no evidence for deviations from the Kerr metric within the 8 orders of magnitude in mass and 16 orders in curvature spanned by the black holes. Future discoveries of coalescing black-hole binaries with low-mass components may help break the degeneracy between deviation parameters.
Article
Physics, Particles & Fields
Aoyun He, Jun Tao, Peng Wang, Yadong Xue, Lingkai Zhang
Summary: In this study, we investigate the shadows of Born-Infeld black holes with magnetic monopoles and Schwarzschild black holes embedded in a uniform Born-Infeld magnetic field. We analyze the effects of nonlinear electromagnetic interactions on the shadow size and the motion of photons in the magnetic field.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Guo-Ping Li, Ke-Jian He
Summary: In this paper, the shadows and rings of the KS black hole in deformed HL gravity were carefully investigated using the ray-tracing method. The results show a decrease in certain parameters and an increase in effective potential with an increase in the omega parameter, with direct emissions dominating the total observed intensity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
A. Belhaj, H. Belmahi, M. Benali
Summary: This study focuses on the shadow aspects of superentropic black holes in four dimensions using the Hamilton-Jacobi formalism. By analyzing the shadow behaviors in celestial coordinates with fixed observer positions, ellipse shaped geometries contrary to usual black hole solutions are observed. The modifications made to the ordinary relations describing geometrical observables lead to discussions on size and shape deformation parameters of these non-trivial geometric forms, as well as exploring the shadow of naked singularities associated with certain mass values.
Article
Materials Science, Multidisciplinary
Aydin Deger, Matthew D. Horner, Jiannis K. Pachos
Summary: One of the key applications of AdS/CFT correspondence is the duality between the entanglement entropy of AdS black holes and lower-dimensional CFTs. By simulating the effect of rotationally symmetric 3D black holes on Dirac fields using a square lattice of fermions with inhomogeneous tunneling couplings, we identify the parametric regime where the predicted 2D CFT accurately describes the black hole entanglement entropy. We also demonstrate that a large family of 3D black holes exhibit the same ground-state entanglement entropy behavior as the BTZ black hole. The simplicity of our simulator allows for direct numerical investigation of various 3D black holes and the potential realization of these experiments with optical lattice technology.
Article
Astronomy & Astrophysics
Kunal Pal, Kuntal Pal, Rajibul Shaikh, Tapobrata Sarkar
Summary: This paper discusses the invariance of observables corresponding to the shadow of a space-time under conformal transformations, and proposes a method to constrain the parameters of gravity theories using this invariance.
Article
Astronomy & Astrophysics
Thomas Bronzwaer, Heino Falcke
Summary: Distinct visual signature occurs in black holes surrounded by optically thin and geometrically thick emission regions, resulting in a sharp-edged dip in brightness coincident with the black hole's shadow. This signature is due to the reduction of intensity observed in rays that intersect the unstable-photon region and the increase of intensity in rays that travel along extended paths near the boundary of the unstable-photon region. The black hole shadow is distinct from the photon ring and is a robust and fairly model-independent observable for accreting black holes in the deep sub-Eddington regime.
ASTROPHYSICAL JOURNAL
(2021)
Article
Physics, Multidisciplinary
Liang Ma, Yi Pang, Hong Lu
Summary: We report the first discovery that in the heterotic string compactified on a 4-torus or equivalently the IIA string compactified on K3, the leading alpha' corrections to the entropy of rotating black strings at fixed conserved charges can be negative. This implies that the correction to the mass of extremal rotating strings is positive, contrary to the standard expectation from the weak gravity conjecture. Our findings suggest that the validity of the positivity of entropy shift due to higher order operators depends on other factors that were previously omitted in the effective field theory analysis.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2023)
Article
Astronomy & Astrophysics
Ming Zhang, Jie Jiang
Summary: This study investigates the nontrivial effects of NUT charges on the shadows of Kerr-Taub-NUT black holes seen by zero-angular-momentum-observers. It is found that as the observer approaches the string singularity, the shadow size can be relatively very small while the distortion is quite large. Additionally, in cases where the string singularity is only located at the south pole axis of the black hole with large NUT charge, the shadow size is maximal for a north pole observer.
Article
Astronomy & Astrophysics
Fabiano F. Santos, Eduardo Folco Capossoli, Henrique Boschi-Filho
Summary: This study investigates the impact of Horndeski gravity on the AdS/BCFT correspondence, analyzing the 3D black hole corresponding to 2D BCFT, studying the changes in boundary entropy and thermodynamic properties, and indicating a restoration of conformal symmetry. The research also includes a study on the influence of Horndeski gravity on the Hawking-Page phase transition, revealing stable and unstable phases in the plane of free energy versus temperature.
Article
Astronomy & Astrophysics
Cristian Erices, Simon Riquelme, Nicolas Zalaquett
Summary: The study examines the issue of black hole scalarization and its compatibility with cosmic inflation and big bang cosmology from an effective field theory (EFT) perspective, revealing a nontrivial interplay between the Wilson coefficients at even the minimal level.
Article
Physics, Particles & Fields
Liang Ma, Yi Pang, H. Lu
Summary: In an effective theory of gravity, higher derivative terms contribute to the corrections of thermodynamic quantities of black holes. This paper extends the property of using only the leading order solution to obtain the next to next to leading order corrections. A formula is proposed to compute the Euclidean action of asymptotically flat black holes at the next to next to leading order using the solution up to and including the next to leading order. Other conserved quantities can be derived from the Euclidean action using standard thermodynamic relations. The formula is verified in examples of pure gravity and Einstein-Maxwell theory extended by 4- and 6-derivative terms. Additionally, it is proven that the physical quantities of asymptotically flat black holes are invariant under field redefinitions based on the formula.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Astronomy & Astrophysics
Rittick Roy, Sunny Vagnozzi, Luca Visinelli
Summary: This study reconsiders the evolution of black hole shadows induced by superradiance and investigates the case of two ultralight bosons. The study finds that gas accretion and gravitational wave radiation have a negligible effect on the results, and the inclusion of an additional ultralight boson does not shorten the shadow evolution time scale.
Article
Physics, Particles & Fields
Da-Zhu Ma, Fang Xia, Dan Zhang, Guo-Yang Fu, Jian-Pin Wu
Summary: In this paper, a systematic and in-depth study on the chaotic dynamics of the string around the conformal black hole is conducted. The transition in chaotic dynamics when the black hole horizon disappears is observed and it provides a possible way to probe the horizon structure of massive bodies. The application of the generalized MSS inequality in asymptotically flat black hole backgrounds is also examined.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
A. Corongiu, V. Venkatraman Krishnan, P. C. C. Freire, M. Kramer, A. Possenti, M. Geyer, A. Ridolfi, F. Abbate, M. Bailes, E. D. Barr, V. Balakrishnan, S. Buchner, D. J. Champion, W. Chen, B. V. Hugo, A. Karastergiou, A. G. Lyne, R. N. Manchester, P. V. Padmanabh, A. Parthasarathy, S. M. Ransom, J. M. Sarkissian, M. Serylak, W. van Straten
Summary: PSR J1910-5959A is a binary millisecond pulsar in orbit around a helium white dwarf companion. By accurately measuring the parameters of this system, including orbital inclination, masses of the stars, and changes in orbital parameters, it has been confirmed to belong to NGC 6752. This study is significant for investigating alternative models of white dwarf structure and cooling.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
E. van der Wateren, C. G. Bassa, S. Cooper, J. -M. Griessmeier, B. W. Stappers, J. W. T. Hessels, V. I. Kondratiev, D. Michilli, C. M. Tan, C. Tiburzi, P. Weltevrede, A. -S. Bak Nielsen, T. D. Carozzi, B. Ciardi, I. Cognard, R. -J. Dettmar, A. Karastergiou, M. Kramer, J. Kuensemoeller, S. Oslowski, M. Serylak, C. Vocks, O. Wucknitz
Summary: LOTAAS is the most sensitive untargeted radio pulsar survey performed at low radio frequencies to date, which has discovered 76 new radio pulsars. This paper reports on the timing solutions of 35 pulsars discovered by LOTAAS and gives an overview of the findings from the full LOTAAS sample of 76 pulsars, discussing their pulse profiles, radio spectra, and timing parameters. The LOTAAS discoveries have on average steeper radio spectra and longer spin periods, as well as lower spin-down rates compared to the known pulsar population.
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
Vishnu Balakrishnan, Paulo C. C. Freire, S. M. Ransom, Alessandro Ridolfi, E. D. Barr, W. Chen, Vivek Venkatraman Krishnan, D. Champion, M. Kramer, T. Gautam, Prajwal V. Padmanabh, Yunpeng Men, F. Abbate, B. W. Stappers, I. Stairs, E. Keane, A. Possenti
Summary: Researchers confirmed the existence of PSR J2140-2311B and determined its orbital parameters using observations from the MeerKAT telescope. This pulsar is in a highly eccentric orbit with a period of 6.2 days and a total mass of 2.53 M-?. Future observations will further determine its mass and detect additional relativistic effects.
ASTROPHYSICAL JOURNAL LETTERS
(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
B. Posselt, A. Karastergiou, S. Johnston, A. Parthasarathy, L. S. Oswald, R. A. Main, A. Basu, M. J. Keith, X. Song, P. Weltevrede, C. Tiburzi, M. Bailes, S. Buchner, M. Geyer, M. Kramer, R. Spiewak, V. Venkatraman Krishnan
Summary: This study presents the largest survey of average profiles of radio pulsars to date, using the same telescope and data reduction software. The results show a significant correlation between the radio luminosity and the spin-down energy of pulsars, contradicting previous assumptions about population synthesis studies. Furthermore, the findings suggest that magnetic dipole braking may not be the dominant factor in the evolution of pulsar rotation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ziwei Wu, William A. Coles, Joris P. W. Verbiest, Krishnakumar Moochickal Ambalappat, Caterina Tiburzi, Jean-Mathias Griessmeier, Robert A. Main, Yulan Liu, Michael Kramer, Olaf Wucknitz, Nataliya Porayko, Stefan Oslowski, Ann-Sofie Bak Nielsen, Julian Y. Donner, Matthias Hoeft, Marcus Brueggen, Christian Vocks, Ralf-Juergen Dettmar, Gilles Theureau, Maciej Serylak, Vladislav Kondratiev, James W. McKee, Golam M. Shaifullah, Ihor P. Kravtsov, Vyacheslav V. Zakharenko, Oleg Ulyanov, Olexandr O. Konovalenko, Philippe Zarka, Baptiste Cecconi, Leon V. E. Koopmans, Stephane Corbel
Summary: Interstellar scattering is used to probe the ionized interstellar medium and can cause corruptions in pulsar timing experiments. Intensity scintillation and pulse broadening are two types of ISS phenomena caused by small-scale electron density fluctuations. While the Kolmogorov spectral exponent can model the electron density power spectrum, the inhomogeneity in the scattering region affects the pulse broadening behavior.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. D. Cameron, M. Bailes, D. J. Champion, P. C. C. Freire, M. Kramer, M. A. McLaughlin, C. Ng, A. Possenti, A. Ridolfi, T. M. Tauris, H. M. Wahl, N. Wex
Summary: PSR J1757-1854 is a double neutron star binary system in our Galaxy, which exhibits relativistic properties and offers a potential for testing relativistic gravity. Through a 6-year observational campaign, we confirmed the presence of geodetic precession in PSR J1757-1854 and updated its timing and mass constraints. However, the precision of the radiative test of gravity is limited by the unknown distance to the pulsar. We also searched for pulsations from the companion neutron star but obtained negative results. Nevertheless, the system presents opportunities for future relativistic tests of gravity, with expected constraints on the change in the semimajor axis and the relativistic orbital deformation parameter.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
S. E. Motta, J. D. Turner, B. Stappers, R. P. Fender, I Heywood, M. Kramer, E. D. Barr
Summary: In a MeerKAT observation, a radio nebula with cometary-like morphology, named 'Mini Mouse', was discovered by chance. The nebula points back towards a previously unidentified candidate supernova remnant. Precise localization using MeerKAT and FAST telescopes revealed a pulsar, PSR J1914+1054g, at the head of the nebula. The characteristics and age of the pulsar suggest a potential association with the proposed remnant.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
S. Johnston, M. Kramer, A. Karastergiou, M. J. Keith, L. S. Oswald, A. Parthasarathy, P. Weltevrede
Summary: Despite the rich phenomenology of radio pulsar polarization properties, the rotating vector model (RVM) remains the best method to determine the beam geometry of pulsars, even after 50 years since its creation. This study applied the RVM to 854 radio pulsars observed with the MeerKAT telescope, providing insights about the pulsar population as a whole. The main findings include the validity of the geometrical interpretation of position angle traverse in the majority of pulsars, the tendency of RVM failure in pulsars with high circular polarization, emission heights below 1000 km for the majority of pulsars regardless of spin period, and the presence of orthogonal mode jumps in about one third of the population. These results are weakly dependent on the pulsar spin-down energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(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)
Review
Physics, Multidisciplinary
Mariafelicia De Laurentis, Ivan de Martino, Riccardo Della Monica
Summary: The Galactic Center (GC) of the Milky Way, due to its proximity, provides a unique opportunity for astronomical observations that investigate phenomena at the edge of astrophysics and fundamental physics. It serves as a laboratory to test the predictions of general relativity, explore alternative theories, study dark matter, and improve our understanding of supermassive compact objects.
REPORTS ON PROGRESS IN PHYSICS
(2023)
Article
Astronomy & Astrophysics
M. Cadoni, M. De Laurentis, I. De Martino, R. Della Monica, M. Oi, A. P. Sanna
Summary: We investigate a nonsingular black hole spacetime with a strong deformation caused by an additional hair, which is hierarchically larger than the Planck scale. This spacetime is an exact solution of Einstein's equations sourced by an anisotropic fluid. The model presents a de Sitter core and slow-decaying corrections to the Schwarzschild solution.
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)