Article
Astronomy & Astrophysics
Tian Zhou, Leonardo Modesto
Summary: Through the study of popular spherically symmetric regular black holes, we have proven that the analytically extended Hayward black hole and the simplest extension of the Culetu-Simpson-Visser's non-analytic smooth black hole are both geodetically incomplete. The huge ambiguity in the extension of nonanalytic spacetimes leads to geodesic incompleteness, and unless all extensions are complete, these spacetimes do not solve the singularity issue. Therefore, we propose several modifications to make these spacetimes geodetically complete in all possible extensions beyond r = 0.
Article
Astronomy & Astrophysics
Cheng Liu, Sen Yang, Qiang Wu, Tao Zhu
Summary: This paper investigates the physical properties and optical appearance of a thin accretion disk around two types of black hole solutions in Einstein-/Ether theory. The effects of the mother field on the energy flux, temperature distribution, and electromagnetic spectrum of the disk are studied in detail. The results show that the mother field only has a certain effect on the central shadow area of the accretion disk.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Alejandro Cruz-Osorio, Lucian Rezzolla, Fabio D. Lora-Clavijo, Jose Antonio Font, Carlos Herdeiro, Eugen Radu
Summary: We present a numerical study of relativistic Bondi-Hoyle-Lyttleton accretion onto a black hole with synchronized hair. The steady-state solutions obtained provide insights into the formation of black holes in the presence of ultralight scalar fields and the possible association between the shock-cone and quasi-periodic oscillations in X-ray light curves.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Anna Ciurlo, Mark R. Morris, Randall D. Campbell, Andrea M. Ghez, Tuan Do, Devin S. Chu
Summary: We present the first observational constraint on the Brackett-gamma (Br gamma) recombination line emission associated with the supermassive black hole at the center of our Galaxy, known as Sgr A*. We derived a stringent upper limit on the Br gamma flux based on 13 years of data combined with the OSIRIS integral field spectrograph at the W. M. Keck Observatory, strongly constraining possible interpretations of emission from this highly underluminous supermassive black hole.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Tiger Yu-Yang Hsiao, Tomotsugu Goto, Tetsuya Hashimoto, Daryl Joe D. Santos, Alvina Y. L. On, Ece Kilerci-Eser, Yi Hang Valerie Wong, Seong Jin Kim, Cossas K-W Wu, Simon C-C Ho, Ting-Yi Lu
Summary: The study discusses the effectiveness of building a Dyson sphere around a black hole, concluding that by collecting different energy sources, a Type II civilization can be sustained. Additionally, measuring spectral energy distributions and radial velocity variations may aid in identifying potential artificial structures.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Miguel Gracia-Linares, Francisco S. Guzman
Summary: We present the accumulation of magnetized supersonic winds onto a rotating black hole in three dimensions and demonstrate the effects of spin-wind orientations on the evolution and morphology of the shock cone. The crucial finding in the magnetized case is the formation of rarified spots where the magnetic field pressure exceeds the gas pressure, leading to the formation of eddies within the shock cone.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Alejandro Aguayo-Ortiz, Olivier Sarbach, Emilio Tejeda
Summary: The choked accretion model transitions a spherically symmetric accretion flow into an inflow-outflow configuration by setting a density contrast between the equatorial and polar regions. This study focuses on accretion of a perfect fluid onto a rotating Kerr black hole, investigating the impact of the black hole's rotation on the flow and demonstrating the robustness of the model.
Article
Astronomy & Astrophysics
M. Shaghaghian
Summary: We have developed a fully set of 3 + 1 formalism of generalized general relativistic magnetohydrodynamic equations to study time-dependent phenomena of plasma surrounding a non-rotating black hole with a dipolar magnetic field. The Ohm law was investigated with respect to the general relativistic phenomena. The magnetofluid flows in three directions and forms a thick disc structure around the central black hole.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Jiawei Liao, Dao-Jun Liu
Summary: We investigated the stationary spherically symmetric accretion of the collisionless Vlasov gas onto a Bardeen regular black hole. Our study proposed a model with a non-uniform distribution of total angular momentum of gas particles, assuming a half-normal distribution. We found that the regularizing parameter in the Bardeen metric has no significant influence on gas accretion, but the distribution of total angular momentum can heavily suppress the mass accretion rate. This effect may be important for understanding the low luminosity observed in Sgr A* and other underluminous sources like M87*.
ASTROPHYSICS AND SPACE SCIENCE
(2022)
Article
Physics, Multidisciplinary
G. Abbas, M. Azam, A. Ditta
Summary: This study investigates the accretion of an isotropic fluid onto a Born-Infeld black hole by formulating key parameters with the help of the barotropic equation of state and conservation laws. The spherically symmetric accretion of stiff fluid, dust fluid, quintessence fluid, and phantom fluid is analyzed, showing different trends in black hole mass change. The results indicate that the black hole mass increases for stiff fluid, dust fluid, and quintessence fluid, but decreases for phantom fluid.
CHINESE JOURNAL OF PHYSICS
(2021)
Article
Astronomy & Astrophysics
Jared R. Rice, Bing Zhang
Summary: When a stellar-mass black hole is embedded in a dense, massive molecular cloud and moves slowly with respect to the ambient medium for an extended period of time, it can significantly grow its mass through Bondi accretion, providing a novel pathway for the formation of massive black holes.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Roberto Soria, Ruican Ma, Lian Tao, Shuang-Nan Zhang
Summary: By revisiting the published results of X-ray and optical studies on the black hole candidate MAXI J0637-430, we have improved the understanding of its system parameters. This black hole is the farthest known from the Galactic Center and has the shortest period among all Galactic black hole X-ray binaries.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Physics, Multidisciplinary
Alisa Galishnikova, Alexander Philippov, Eliot Quataert, Fabio Bacchini, Kyle Parfrey, Bart Ripperda
Summary: We use axisymmetric general-relativistic particle-in-cell simulations to study the accretion of collisionless plasma onto a rotating black hole. Comparisons with analogous general-relativistic magnetohydrodynamic simulations reveal three key differences between the kinetic and fluid simulations. Our kinetic approach shows more efficient magnetic reconnection, which rapidly accelerates a nonthermal particle population. The plasma in the kinetic simulations also develops significant deviations from thermal equilibrium, including pressure anisotropy that excites kinetic-scale instabilities and a large field-aligned heat flux near the horizon.
PHYSICAL REVIEW LETTERS
(2023)
Article
Astronomy & Astrophysics
Juliano C. S. Neves
Summary: The study presents complete and analytic solutions of regular black holes in a brane context, where the metrics are regular on both the four-dimensional brane and the five-dimensional bulk. The regular black holes have a de Sitter core on the brane and extend to the extra dimension as five-dimensional objects from the bulk perspective.
Article
Astronomy & Astrophysics
Mariko Nomura, Kazuyuki Omukai, Ken Ohsuga
Summary: The study reveals that in high metallicity and large BH mass environments, more dense and fast disc winds appear, which suppress the mass accretion rate. Through simulations and modeling, it is found that the metallicity dependence of the line force and the BH mass dependence of the wind launch region's surface area are the reasons for the metallicity dependence and BH mass dependencies of the mass-loss rate.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Physics, Multidisciplinary
M. Umair Shahzad, Abdul Jawad, Farhad Ali, G. Abbas
Summary: In this study, we have developed a time conformal slowly rotating Kerr black hole using the approximate Noether symmetry approach. Numerical solutions were obtained for geodesics of both lowly rotating Kerr black hole and time conformal slowly rotating Kerr black hole. The dynamics of neutral and charged particles moving around the time conformal slowly rotating Kerr black hole were discussed in the absence/presence of a magnetic field. The behavior of effective force, effective potential, and escape velocity of particles near the event horizon in the absence/presence of a magnetic field were analyzed graphically. The conditions under which particles can escape from the black hole after collision with another particle were examined. Unstable orbits of particles near the event horizon were found due to the effect of magnetic field and angular momentum.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Physics, Multidisciplinary
Qanitah Ama-Tul-Mughani, Arfa Waseem, Wardat Us Salam, Abdul Jawad
Summary: This paper investigates the greybody factor and thermodynamic properties of rotating and regular black holes in the vicinity of perfect fluid dark matter. By converting equations and performing calculations, it is concluded that the attractiveness of the black hole decreases, leading to a decrease in the greybody factor, as the rotation parameter and strength of the dark matter reduce. The entropy of the black hole is also found to increase with larger values of the rotation parameter.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Physics, Mathematical
Abdul Malik Sultan, Abdul Jawad
Summary: In this study, we investigate the cosmological and thermodynamic aspects of Weyl tensor corrected f(R) gravity and propose some cosmological parameters based on well-known cosmological bouncing scenarios. The results show that the stability of the models and the validity of the generalized second law of thermodynamics are influenced by certain factors.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Article
Physics, Multidisciplinary
A. H. Ziaie, H. Moradpour, V. B. Bezerra, A. Jawad
Summary: This study investigates the Sagnac effect in exact spacetimes representing rotating black holes and naked singularities. The results indicate that the Sagnac time delay is influenced by the presence of extra-dimensions and angular momentum. Furthermore, the time delay differs between the spacetime of a naked singularity and that of a black hole. Therefore, the Sagnac effect can be utilized as an experimental tool to enhance our understanding of spacetimes with higher dimensions or those that include naked singularities.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Astronomy & Astrophysics
Abdul Jawad, Sadaf Maqsood
Summary: This paper utilizes dynamical system techniques to study the stability analysis of Friedmann-like spacetime in the presence of torsion. By converting the equations of motion into a first order autonomous system of differential equations and introducing an ansatz for the torsion term, the effects of various forms of interaction on stability are examined. It is found that the cosmological solutions can describe different evolutionary phases and exhibit stable attractor behavior.
ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Mathematical
Abdul Jawad, Shamaila Rani, Sameen Ashraf, Nadeem Azhar
Summary: We discuss the cosmological implications of the interacting Barrow holographic dark energy model in the context of flat deformed Horava-Lifshitz gravity by assuming the interaction between dark energy and pressureless dark matter. We investigate the evolutionary history of cosmological parameters and find results that favor observational data of Planck 2018. Moreover, we examine the generalized second law of thermodynamics of this cosmological system with barrow entropy as horizon entropy and observe that this law holds for both horizons.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Article
Astronomy & Astrophysics
Shamaila Rani, Iram Ashraf, Abdul Jawad
Summary: This paper explores squared speed of sound models in the context of nonzero torsion theory for flat FRW spacetime, discussing the accelerated expansion of the universe using cosmological parameters and examining the validity of the generalized second law of thermodynamics for each model. The results show consistent behavior and constraints on model parameters for accelerated expansion, with implications for the EoS parameter in quintessence, cosmological constant, and phantom eras.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Physics, Mathematical
Shamaila Rani, Muhammad Bilal Amin Sulehri, Abdul Jawad, Usman Zafar
Summary: This work examines the properties of wormholes in the framework of f(T) gravity, using Casimir energy density as an exotic matter source. The behavior of shape function, equation of state parameters, energy conditions, and stability conditions for wormholes are analyzed. The study also investigates the impact of the generalized uncertainty principle on wormhole properties in f(T) gravity.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
Shamaila Rani, Abdul Jawad, Abdul Malik Sultan, Aneesa Majeed
Summary: We investigate the swampland conjectures of quintessence and tachyon scalar field models in f(T) and Einstein gravities. Constraints on de-Sitter conjectures are developed through the Bekenstein entropy relation in the cold and warm inflationary scenarios. The results show that the de-Sitter conjecture constraint is satisfied for specific choices of constants in both scenarios.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Physics, Multidisciplinary
Shamaila Rani, Aimen Javed, Abdul Jawad
Summary: This paper explores the gravitational baryogenesis mechanism in the context of (R, P) theory of gravity, and considers five different models for (R, P) gravity. The authors calculate the baryon number density to entropy ratio for each model, and highlight the optimal model parameter values consistent with observational data.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Multidisciplinary
Abdul Jawad, Muhammad Usman
Summary: In this article, we studied the dynamical stability of cosmic models and their cosmographic parameters within the framework of deformed Horava-Liftshiz gravity. We used a dynamical analysis approach to investigate four interaction models with varying vacuum dark energy. Our results showed that, except for one, all critical points in different interaction models were stable and exhibited attractive behavior. Additionally, the cosmographic parameters were consistent with recent cosmic observations and represented the quintessence era under the stability conditions of different cosmic models.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Multidisciplinary
Abdul Jawad, Usman Zafar, Muhammad Saleem, Rubab Manzoor
Summary: In the presence of exponential corrected entropy, the thermal stability and phase transitions of a charged 4D Einstein-Gauss-Bonnet-AdS black hole are investigated using the deflection angle formalism. The phase structure of the black hole is studied through an analysis of the optical aspects employing elliptic functions. The thermal variation of the deflection angle is found to generate both stable and unstable phases, and the Hawking-Page phase transition is investigated based on the Gibbs free energy optical dependence. Furthermore, specific points along the deflection angle lead to transitions between large and small black holes. The critical behavior of AdS black holes can be determined by studying the Gibbs free energy versus deflection angle behavior. The thermodynamic geometry of the charged 4D Einstein-Gauss-Bonnet-AdS black hole is also discussed in the presence of exponential corrected entropy.
Article
Astronomy & Astrophysics
Abdul Jawad, Mazhar Hussain, Shamaila Rani
Summary: In this paper, the thermal stability and thermodynamic geometries of non-rotating/rotating charged black holes are investigated. The physical quantities such as mass and temperature of the system are determined using barrow entropy, and their stability is found through the first and second phase transitions of the heat capacity. The effects of scalar charge Q and hair parameter lambda on black hole properties are analyzed by considering both positive and negative values of these parameters. It is observed that heat capacity provides the stable, unstable regions, and phase transition points for both black holes. Various techniques such as Ruppeiner, Weinhold, Quevedo, and HPEM metrics are considered to analyze the thermodynamic geometry of these black holes. It is found that Weinhold, Quevedo, and HPEM exhibit attractive/repulsive behavior of particles in the stable/unstable regions of black holes.
Article
Astronomy & Astrophysics
Abdul Jawad, Shamaila Rani, Farzan Mushtaq
Summary: This paper studies cosmological models in two gravitational theories, including fractal universe and dynamical Chern-Simons modified theory. In both theories, three particle creation rate models, constant and variable mode, are considered. Gibbs equation is used to calculate the pressure of particle creation rate using the adiabatic matter phenomenon. The Hubble parameter and its normalized form are constructed for each case. The deceleration parameter and effective equation of state parameter are discussed by considering the normalized Hubble parameter and model parameters. The results of these parameters show consistent behavior with recent observational data.
Article
Astronomy & Astrophysics
Shahid Chaudhary, Abdul Jawad, Muhammad Yasir
Summary: This work investigates the thermodynamic geometry of spherically symmetric black holes in AdS spacetime, revealing that enthalpy is the central thermodynamic quantity and identifying the curvatures and repulsive interaction information among black hole molecules in different phase spaces. Additionally, the thermal stability of AdS black holes in Einstein-Maxwell-scalars theory and regularized Lovelock theory is analyzed, with the observation that momentum relaxation parameter and coupling constants increase the thermal stability of the black holes. The study also delves into the Joule-Thomson expansion for black holes in regularized Lovelock theory.
