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Resolved Magnetic-Field Structure and Variability Near the Event Horizon of Sagittarius A*
Michael D. Johnson, Vincent L. Fish, Sheperd S. Doeleman +45
Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. The…
Computational Imaging for VLBI Image Reconstruction
Katherine L. Bouman, Michael D. Johnson, Daniel Zoran +3
Very long baseline interferometry (VLBI) is a technique for imaging celestial radio emissions by simultaneously observing a source from telescopes distributed across Earth. The cha…
Unbound Debris Streams and Remnants Resulting From the Tidal Disruptions of Stars by Supermassive Black Holes
James Guillochon, Michael McCourt, Xian Chen +2
The kinetic energy of a star in orbit about a supermassive black hole is a significant fraction of its rest mass energy when its periapse is comparable to its tidal radius. Upon it…
230 GHz VLBI observations of M87: event-horizon-scale structure at the enhanced very-high-energy -ray state in 2012
Kazunori Akiyama, Ru-Sen Lu, Vincent L. Fish +45
We report on 230 GHz (1.3 mm) VLBI observations of M87 with the Event Horizon Telescope using antennas on Mauna Kea in Hawaii, Mt. Graham in Arizona and Cedar Flat in California. F…
Measuring the Direction and Angular Velocity of a Black Hole Accretion Disk via Lagged Interferometric Covariance
Michael D. Johnson, Abraham Loeb, Hotaka Shiokawa +2
We show that interferometry can be applied to study irregular, rapidly rotating structures, as are expected in the turbulent accretion flow near a black hole. Specifically, we anal…
Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
Michael D. Johnson, Carl R. Gwinn
At radio wavelengths, scattering in the interstellar medium distorts the appearance of astronomical sources. Averaged over a scattering ensemble, the result is a blurred image of t…