412 citations · 3.1k across the 30 of their papers we have counts for
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Testing General Relativity with Accretion-Flow Imaging of Sgr A*
Tim Johannsen, Carlos Wang, Avery E. Broderick +4
The Event Horizon Telescope is a global very-long baseline interferometer capable of probing potential deviations from the Kerr metric, which is believed to provide the unique desc…
Modeling Seven Years of Event Horizon Telescope Observations with Radiatively Inefficient Accretion Flow Models
Avery E. Broderick, Vincent L. Fish, Michael D. Johnson +6
An initial three-station version of the Event Horizon Telescope, a millimeter-wavelength very-long baseline interferometer, has observed Sagittarius A* (Sgr A*) repeatedly from 200…
Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum
Tim Johannsen
According to the general-relativistic no-hair theorem, astrophysical black holes depend only on their masses and spins and are uniquely described by the Kerr metric. Mass and spin…
Magnetised Accretion Discs in Kerr Spacetimes II: Hot Spots
Federico García, Ignacio F. Ranea-Sandoval, Tim Johannsen
Context. Quasi-periodic variability has been observed in a number of X-ray binaries harboring black hole candidates. In general relativity, black holes are uniquely described by th…
X-ray Probes of Black Hole Accretion Disks for Testing the No-Hair Theorem
Tim Johannsen
The spins of a number of supermassive and stellar-mass black holes have been measured based on detections of thermal continuum emission and relativistically broadened iron lines in…
Photon Rings around Kerr and Kerr-like Black Holes
Tim Johannsen
Very-long baseline interferometric observations have resolved structure on scales of only a few Schwarzschild radii around the supermassive black holes at the centers of our Galaxy…
Testing the No-Hair Theorem with Event Horizon Telescope Observations of Sagittarius A*
Avery E. Broderick, Tim Johannsen, Abraham Loeb +1
The advent of the Event Horizon Telescope (EHT), a millimeter-wave very-long baseline interferometric array, has enabled spatially-resolved studies of the sub-horizon-scale structu…
Testing General Relativity in the Strong-Field Regime with Observations of Black Holes in the Electromagnetic Spectrum
Tim Johannsen
General relativity has been tested by many experiments, which, however, almost exclusively probe weak spacetime curvatures. In this thesis, I create two frameworks for testing gene…
Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum. IV. Relativistically Broadened Iron Lines
Tim Johannsen, Dimitrios Psaltis
According to the no-hair theorem, astrophysical black holes are fully characterized by their masses and spins and are described by the Kerr metric. This theorem can be tested obser…
A Ray-Tracing Algorithm for Spinning Compact Object Spacetimes with Arbitrary Quadrupole Moments. II. Neutron Stars
Michi Baubock, Dimitrios Psaltis, Feryal Ozel +1
A moderately spinning neutron star acquires an oblate shape and a spacetime with a significant quadrupole moment. These two properties affect its apparent surface area for an obser…
Testing the No-Hair Theorem with Sgr A*
Tim Johannsen
The no-hair theorem characterizes the fundamental nature of black holes in general relativity. This theorem can be tested observationally by measuring the mass and spin of a black…
Sgr A*: The Optimal Testbed of Strong-Field Gravity
Dimitrios Psaltis, Tim Johannsen
The black hole in the center of the Milky Way has been observed and modeled intensely during the last decades. It is also the prime target of a number of new experiments that aim t…
A Ray-Tracing Algorithm for Spinning Compact Object Spacetimes with Arbitrary Quadrupole Moments. I. Quasi-Kerr Black Holes
Dimitrios Psaltis, Tim Johannsen
We describe a new numerical algorithm for ray tracing in the external spacetimes of spinning compact objects characterized by arbitrary quadrupole moments. Such spacetimes describe…
Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-Periodic Variability
Tim Johannsen, Dimitrios Psaltis
According to the no-hair theorem, astrophysical black holes are uniquely described by their masses and spins. An observational test of the no-hair theorem can be performed by measu…
Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum
Tim Johannsen, Dimitrios Psaltis
According to the no-hair theorem, astrophysical black holes are uniquely described by their mass and spin. In this paper, we review a new framework for testing the no-hair hypothes…
Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images
Tim Johannsen, Dimitrios Psaltis
According to the no-hair theorem, all astrophysical black holes are fully described by their masses and spins. This theorem can be tested observationally by measuring (at least) th…
Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: I. Properties of a Quasi-Kerr Spacetime
Tim Johannsen, Dimitrios Psaltis
According to the no-hair theorem, an astrophysical black hole is uniquely described by only two quantities, the mass and the spin. In this series of papers, we investigate a framew…
Testing the No-Hair Theorem with Observations of Astrophysical Black Holes in the Electromagnetic Spectrum
Dimitrios Psaltis, Tim Johannsen
The Kerr spacetime of spinning black holes is one of the most intriguing predictions of Einstein's theory of general relativity. The special role this spacetime plays in the theory…