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There is strong observational evidence that almost every large galaxy has a supermassive black hole at its center. It is of fundamental importance to know whether such black holes are described by the standard Kerr solution in General…

General Relativity and Quantum Cosmology · Physics 2024-06-14 Eugeny Babichev , Christos Charmousis , Daniela D. Doneva , Galin N. Gyulchev , Stoytcho S. Yazadjiev

We present a simple formula for the effective ringdown frequencies of the gravitational-wave signal of a precessing black-hole binary in the co-precessing frame. This formula requires only knowledge of the quasi-normal mode frequencies of…

General Relativity and Quantum Cosmology · Physics 2023-05-24 Eleanor Hamilton , Lionel London , Mark Hannam

Here we construct approximate analytical forms for the metric coefficients and fields representing the scalarized Einstein-Maxwell black holes with various couplings of the scalar field, once the parameters of the system are fixed. By…

General Relativity and Quantum Cosmology · Physics 2019-08-12 R. A. Konoplya , A. Zhidenko

Random feature methods have been successful in various machine learning tasks, are easy to compute, and come with theoretical accuracy bounds. They serve as an alternative approach to standard neural networks since they can represent…

Machine Learning · Statistics 2026-01-21 Abolfazl Hashemi , Hayden Schaeffer , Robert Shi , Ufuk Topcu , Giang Tran , Rachel Ward

We investigate how the speed of gravitational waves, $c_{GW}$, can be tested by upcoming black hole ringdown observations. We do so in the context of hairy black hole solutions, where the hair is associated with a new scalar degree of…

General Relativity and Quantum Cosmology · Physics 2024-08-27 Sergi Sirera , Johannes Noller

The co-evolution of a supermassive black hole with its host galaxy through cosmic time is encoded in its spin. At $z>2$, supermassive black holes are thought to grow mostly by merger-driven accretion leading to high spin. However, it is…

High Energy Astrophysical Phenomena · Physics 2014-03-21 Rubens C. Reis , Mark T. Reynolds , Jon M. Miller , Dominic J. Walton

Over the last decades X-ray spectroscopy has proven to be a powerful tool for the estimation of black hole spin and several other key parameters in dozens of AGN and black hole X-ray binaries. In this White Paper, we discuss the…

We derive closed formulas for the mass and spin parameters of a Kerr black hole in terms of a minimal quantity of observational data: the red-/blue-shifts of photons emitted by massive particles (stars) moving on geodesics around the black…

General Relativity and Quantum Cosmology · Physics 2021-02-17 Alfredo Herrera-Aguilar , Raúl Lizardo-Castro , Ulises Nucamendi

The black hole uniqueness and the no-hair theorems imply that the quasinormal spectrum of any astrophysical black hole is determined solely by its mass and spin. The countably infinite number of quasinormal modes of a Kerr black hole are…

General Relativity and Quantum Cosmology · Physics 2020-08-31 Xisco Jiménez Forteza , Swetha Bhagwat , Paolo Pani , Valeria Ferrari

Accretion disk reflection spectra, including broad iron emission lines, bear the imprints of the strong Doppler shifts and gravitational red-shifts close to black holes. The extremity of these shifts depends on the proximity of the…

High Energy Astrophysical Phenomena · Physics 2010-01-15 J. M. Miller , C. S. Reynolds , A. C. Fabian , G. Miniutti , L. C. Gallo

Inaccurate modeling of gravitational-wave signals can introduce systematic biases in the inferred source parameters. As detector sensitivities improve and signals become louder, mitigating such waveform-induced systematics becomes…

General Relativity and Quantum Cosmology · Physics 2026-03-13 Lodovico Capuano , Massimo Vaglio , Rohit S. Chandramouli , Chantal L Pitte , Adrien Kuntz , Enrico Barausse

In this work, we elaborate on the development of a general relativistic formalism that allows one to analytically express the mass and spin parameters of the Kerr black hole in terms of observational data: the total redshift and blueshift…

General Relativity and Quantum Cosmology · Physics 2022-06-30 Pritam Banerjee , Alfredo Herrera-Aguilar , Mehrab Momennia , Ulises Nucamendi

Gravitational waves from extreme mass-ratio inspirals (EMRIs) will enable sub-percent measurements of massive black hole parameters and provide access to the demographics of compact objects in galactic nuclei. During the LISA mission,…

High Energy Astrophysical Phenomena · Physics 2026-01-22 Shashwat Singh , Christian E. A. Chapman-Bird , Christopher P. L. Berry , John Veitch

Future space-based gravitational wave (GW) observatories such as LISA will detect massive black hole binaries (MBHBs), which are expected to be accompanied by electromagnetic counterparts, thereby providing bright standard sirens for…

Instrumentation and Methods for Astrophysics · Physics 2026-03-06 Jia-Hao Zhong , Jin-Zhao Yang , Tao Yang , Xu-Heng Ding , Xi-Long Fan , Kai Liao , Bei You

There is robust observational evidence supporting the existence of $5 - 20$ $M_\odot$ compact bodies in X-ray binary systems and of $10^5 - 10^9$ $M_\odot$ bodies at the center of many galaxies. All these objects are commonly interpreted as…

General Relativity and Quantum Cosmology · Physics 2011-05-12 Cosimo Bambi

We present a unified theoretical framework for parametric low-rank approximation, a research area devoted to the development of efficient algorithms that act as adaptive alternatives of traditional methods such as Singular Value…

Numerical Analysis · Mathematics 2025-09-22 Nicola Rares Franco

We numerically compute the ringdown amplitudes following the plunge of a particle from the innermost stable circular orbit (ISCO) of a Schwarzschild black hole in the extreme-mass ratio limit. We show that the ringdown amplitudes computed…

General Relativity and Quantum Cosmology · Physics 2011-08-12 Shahar Hadar , Barak Kol , Emanuele Berti , Vitor Cardoso

The coalescences of stellar-mass black-hole binaries through their inspiral, merger, and ringdown are among the most promising sources for ground-based gravitational-wave (GW) detectors. If a GW signal is observed with sufficient…

We analyze the population statistics of black holes in the LIGO/Virgo/KAGRA GWTC-3 catalog using a parametric mass function derived from simulations of massive stars experiencing pulsational pair-instability supernovae (PPISN). Our…

High Energy Astrophysical Phenomena · Physics 2024-06-11 Yannick Ulrich , Djuna Croon , Jeremy Sakstein , Samuel McDermott

In recent works, a framework has been developed to describe (quantum) deformed, spherically symmetric and static black holes in four dimensions. The key idea of this so-called Effective Metric Description (EMD) is to parametrise…

General Relativity and Quantum Cosmology · Physics 2025-08-26 Stefan Hohenegger