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Being one of only two fundamental properties black holes possess, the spin of supermassive black holes (SMBHs) is of great interest for understanding accretion processes and galaxy evolution. However, in these early days of spin…

Instrumentation and Methods for Astrophysics · Physics 2016-03-16 K. Bonson , L. C. Gallo

From the formation mechanisms of stars and compact objects to nuclear physics, modern astronomy frequently leverages surveys to understand populations of objects to answer fundamental questions. The population of dark and isolated compact…

Black hole images are theoretically predicted (under mild astrophysical assumptions) to display a stack of lensed "photon rings" that carry information about the underlying spacetime geometry. Despite vigorous efforts, no such ring has been…

General Relativity and Quantum Cosmology · Physics 2023-09-25 Alejandro Cárdenas-Avendaño , Alexandru Lupsasca

Identifying weak gravitational wave signals in noise and estimating the source properties require high-precision waveform templates. Numerical relativity (NR) simulations can provide the most accurate waveforms. However, it is challenging…

General Relativity and Quantum Cosmology · Physics 2025-03-07 Xing-Yu Zhong , Wen-Biao Han , Ling Sun

Measurements from the Event Horizon Telescope enabled the visualization of light emission around a black hole for the first time. So far, these measurements have been used to recover a 2D image under the assumption that the emission field…

Computer Vision and Pattern Recognition · Computer Science 2022-04-11 Aviad Levis , Pratul P. Srinivasan , Andrew A. Chael , Ren Ng , Katherine L. Bouman

General Relativity predicts that the emission close to a black hole must be lensed by its strong gravitational field, illuminating the last photon orbit. This results in a dark circular area known as the black hole 'shadow'. The Event…

Instrumentation and Methods for Astrophysics · Physics 2016-09-02 Leonid Benkevitch , Kazunori Akiyama , Rusen Lu , Shepherd Doeleman , Vincent Fish

We present a new reconstruction of the Event Horizon Telescope (EHT) image of the M87 black hole from the 2017 data set. We use PRIMO, a novel dictionary-learning based algorithm that uses high-fidelity simulations of accreting black holes…

High Energy Astrophysical Phenomena · Physics 2023-04-14 Lia Medeiros , Dimitrios Psaltis , Tod R. Lauer , Feryal Ozel

This study investigates the visual characteristics of a rotating black hole (BH) within the fabric of $4$D Einstein-Gauss-Bonnet gravity illuminated with two illumination models, such as a celestial light sphere and a thin accretion disk.…

High Energy Astrophysical Phenomena · Physics 2026-04-22 Muhammad Israr Aslam , Manahil Ali , Abdul Malik Sultan , Xiao-Xiong Zeng , Sultan Hussain

The Event Horizon Telescope (EHT) images of the supermassive black hole at the center of the galaxy M 87 provided the first image of the accretion environment on horizon scales. General relativity predicts that the image of the shadow…

High Energy Astrophysical Phenomena · Physics 2022-12-14 Paul Tiede , Avery E. Broderick , Daniel C. M. Palumbo , Andrew Chael

(abridged) The black hole Sagittarius A* (Sgr A*) is a prime target for next-generation Earth-space very-long-baseline interferometry missions such as the Black Hole Explorer (BHEX), which aims to probe baselines of the order of 20…

High Energy Astrophysical Phenomena · Physics 2025-07-16 Aditya Tamar , Ben Hudson , Daniel C. M. Palumbo

Blurred reflection features are commonly observed in the X-ray spectra of accreting black holes. In the presence of high-quality data and with the correct astrophysical model, X-ray reflection spectroscopy is a powerful tool to probe the…

High Energy Astrophysical Phenomena · Physics 2025-10-15 Cosimo Bambi

Black hole X-ray binaries (BHBs) offer insights into extreme gravitational environments and the testing of general relativity. The X-ray spectrum collected by NICER offers valuable information on the properties and behaviour of BHBs through…

Instrumentation and Methods for Astrophysics · Physics 2024-04-03 Ethan Tregidga , James Steiner , Cecilia Garraffo , Carter Rhea , Mayeul Aubin

The Event Horizon Telescope (EHT) collaboration has recently released the first image of a black hole (BH), opening a new window onto tests of general relativity in the strong field regime. In this paper, we derive constraints on the nature…

General Relativity and Quantum Cosmology · Physics 2020-02-24 Cosimo Bambi , Katherine Freese , Sunny Vagnozzi , Luca Visinelli

The 2017 Event Horizon Telescope (EHT) observations of M87* detected a ring-shaped feature $\sim40\mu$as in diameter, consistent with the event horizon scale of a black hole of the expected mass. The thickness of this ring, however, proved…

High Energy Astrophysical Phenomena · Physics 2022-10-05 Will Lockhart , Samuel E. Gralla

We discuss the fundamentals of classical black hole (BH) thermodynamics in a new framework determined by light surfaces and their frequencies. This new approach allows us to study BH transitions inside the Kerr geometry. In the case of BHs,…

General Relativity and Quantum Cosmology · Physics 2022-06-01 D. Pugliese , H. Quevedo

Constraining the primary growth channel of supermassive black holes (SMBH) remains one the most actively debated questions in the context of cosmological structure formation. Owing to the expected connection between SMBH spin parameter…

This work describes the motion of photons in black hole (BH) spacetimes within the framework of Horndeski theory. We focus on the shadows, quasinormal modes (QNMs) and optical appearances of BHs surrounded by geometrically thin accretion…

General Relativity and Quantum Cosmology · Physics 2024-07-23 Zhi Luo , Jin Li , Ke-Jian He , Hao Yu

The recent advent of the Event Horizon Telescope (EHT) has made direct imaging of supermassive black holes a reality. Simulated images of black holes produced via general relativistic ray tracing and radiative transfer provide a key…

High Energy Astrophysical Phenomena · Physics 2021-05-13 Z. Gelles , B. S. Prather , D. C. M. Palumbo , M. D. Johnson , G. N. Wong , B. Georgiev

High-precision regression of physical parameters from black hole images generated by General Relativistic Ray Tracing (GRRT) is essential for investigating spacetime curvature and advancing black hole astrophysics. However, due to…

Instrumentation and Methods for Astrophysics · Physics 2025-07-23 Jialei Wei , Ao Liu , Dejiang Li , Cuihong Wen

The knowledge about the black hole mass function (BHMF) and its evolution would help to understand the origin of the BHs and how BH binaries formed at different stages of the history of the Universe. We demonstrate the ability of future…

Astrophysics of Galaxies · Physics 2020-03-11 Xuheng Ding , Kai Liao , Marek Biesiada , Zong-Hong Zhu