# EHT 2014

EHT 2014

## Discussion 5

Wednesday Nov 12, 2014
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## Testing General Relativity with the EHT

Wednesday Nov 12, 2014
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In general relativity, astrophysical black holes are characterized uniquely in terms of their masses and spins and are described by the Kerr metric. The high sensitivity and resolution of the EHT will allow for unprecedented tests of the Kerr nature of black holes and, hence, of general relativity. I will present current and future limits on deviations from the Kerr metric from Sgr A* in the context of radiatively-inefficient accretion flow models.

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## Neutron Stars in the Galactic Center

Wednesday Nov 12, 2014
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I will discuss the prospects for finding additional radio pulsars in the Galactic center region and their utility for probing general relativity and other constituents in the region. This will include discussions of neutron star populations; radio wave scattering in and toward the Galactic center; issues and progress in discovering pulsars; and the precision to which discoverable pulsars can be timed

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## GRAVITY - Exploring Physics Close to the Galactic Center Black Hole with Infrared Interferometry

Wednesday Nov 12, 2014
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GRAVITY is a new instrument combining the four 8m ESO Very Large Telescopes in Chile. Other than the BlackHoleCam / EHT with its focus on imaging the shadow of the black hole against the surrounding accretion flow, the goal of GRAVITY is to measure dynamical processes in the immediate vicinity of the black hole, for example the motion of matter close to the last stable orbit and relativistic effects in stellar orbits.

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## Gas Dynamical Black Hole Mass Measurements for M87

Wednesday Nov 12, 2014
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M87 is one of the most luminous nearby galaxies and hosts one of the most massive black holes known, making it a very important target for extragalactic studies. The supermassive black hole has been the subject of several stellar and gas dynamical mass measurements; however, the best current stellar dynamical black hole mass is larger than the gas dynamical determination by a factor of two, corresponding to a 2-sigma discrepancy.

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## Detecting gravitational waves from supermassive binary black holes with pulsar timing

Wednesday Nov 12, 2014
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I will discuss the current status of the NANOGrav pulsar timing array, and the prospects for a detection of the stochastic background produced by the mergers of supermassive black holes.

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## Advanced LIGO status and prospects to probe the strong gravity regime

Wednesday Nov 12, 2014
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Gravitational waves will allow scientists to test Einstein?s theory of General Relativity in the previously unexplored strong-field regime. Einstein?s theory of general relativity, as the most accepted theory of gravity, has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves may carry information about highly dynamical and strong-field gravity that is required to generate measurable waves.

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## Fuzzballs, Firewalls and all that

Wednesday Nov 12, 2014
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Some 40 years ago Hawking showed that if the black hole has a smooth horizon, then information will be lost when the black hole radiates. In string theory black holes appear to have a complete set of hair'; these black hole states are called fuzzballs, and they radiate like normal bodies with no information loss. It was recently argued that structure at the horizon will necessarily feel like a firewall' to an infalling observer.

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## Discussion 4

Tuesday Nov 11, 2014
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## Horizon Scale Lepton Acceleration in Jets: Explaining the Compact Radio Emission in M87

Tuesday Nov 11, 2014

It has now become clear that the radio jet in the giant elliptical galaxy M87 must turn on very close to the black hole. This implies the efficient acceleration of leptons within the jet at scales much smaller than feasible by the typical dissipative events usually invoked to explain jet synchrotron emission. Here we show that the stagnation surface, the separatrix between material that falls back into the black hole and material that is accelerated outward forming the jet, is a natural site of pair formation and particle acceleration.

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## LECTURES ON-DEMAND

### Gabriela González, Louisiana State University

Speaker: Gabriela Gonzalez