412 citations · 3.1k across the 30 of their papers we have counts for
30 papers
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…
Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales
Vincent L. Fish, Michael D. Johnson, Sheperd S. Doeleman +69
The Galactic Center black hole Sagittarius A* (Sgr A*) is a prime observing target for the Event Horizon Telescope (EHT), which can resolve the 1.3 mm emission from this source on…
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…
Testing General Relativity with the Shadow Size of Sgr A*
Tim Johannsen, Avery E. Broderick, Philipp M. Plewa +7
In general relativity, the angular radius of the shadow of a black hole is primarily determined by its mass-to-distance ratio and depends only weakly on its spin and inclination. I…
Sgr A* and General Relativity
Tim Johannsen
General relativity has been widely tested in weak gravitational fields but still stands largely untested in the strong-field regime. According to the no-hair theorem, black holes i…
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…
Regular Black Hole Metric with Three Constants of Motion
Tim Johannsen
According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric spacetimes…
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…
High-Angular-Resolution and High-Sensitivity Science Enabled by Beamformed ALMA
Vincent Fish, Walter Alef, James Anderson +66
An international consortium is presently constructing a beamformer for the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile that will be available as a facility instrum…
Inner Accretion Disk Edges in a Kerr-Like Spacetime
Tim Johannsen
According to the no-hair theorem, astrophysical black holes are uniquely described by the Kerr metric. In order to test this theorem with observations in either the electromagnetic…
Systematic Study of Event Horizons and Pathologies of Parametrically Deformed Kerr Spacetimes
Tim Johannsen
In general relativity, all black holes in vacuum are described by the Kerr metric, which has only two independent parameters: the mass and the spin. The unique dependence on these…
A Metric for Testing the Nature of Black Holes
Tim Johannsen
In general relativity, astrophysical black holes are uniquely described by the Kerr metric. Observational tests of the Kerr nature of these compact objects and, hence, of general r…
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…
Masses of Nearby Supermassive Black Holes with Very-Long Baseline Interferometry
Tim Johannsen, Dimitrios Psaltis, Stefan Gillessen +4
Dynamical mass measurements to date have allowed determinations of the mass M and the distance D of a number of nearby supermassive black holes. In the case of Sgr A*, these measur…
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…
A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem
Tim Johannsen, Dimitrios Psaltis
According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric deviations…
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…