EHT 2014

EHT 2014

 

 

Tuesday Nov 11, 2014
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Monday Nov 10, 2014
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Monday Nov 10, 2014
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The radio community pioneered the use of closure phases to allow interferometric imaging even when fringe phases are compromised by atmospheric turbulence or unstable reference clocks. Eventually, better receivers and observing methods allowed phase referencing to provide direct measures of complex visibilities and eased the uncertainties using Fourier inversions required for imaging.

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Monday Nov 10, 2014

The Event Horizon Telescope has measured compact emission in Sgr A* and M87 at resolutions comparable to their event horizons. Polarimetry with the EHT enables a powerful extension of this work, mapping magnetic field structures via the highly polarized synchrotron emission that is thought to dominate the compact emission. Sgr A* provides an especially attractive target for linear polarization studies with the EHT because it is unpolarized at the longer wavelengths where facility instruments are available.

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Monday Nov 10, 2014
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Closure phases measured on the Arizona-California-Hawaii triangle of the EHT over multiple years indicate that the 1.3 mm structure of Sgr A* is asymmetric on scales of a few Schwarzschild radii. The closure phase data provide new constraints on models of the quiescent emission from Sgr A*. Time variability in the closure provides evidence of structural changes on scales resolved by millimeter-wavelength VLBI.
We discuss these results as well as other implications of the data.

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Monday Nov 10, 2014
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Monday Nov 10, 2014
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I summarize several physical processes that can produce efficient particle acceleration in radiatively inefficient accretion flows. I then describe the implications for non-thermal emission and EHT observations of Sgr A*.

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Monday Nov 10, 2014
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Long wavelength measurements provide sensitive probes of the intrinsic structure of Sgr A* and of the scattering properties of the line-of-sight interstellar medium. At this wavelength, scattering dominates the apparent size of the source but careful closure amplitude techniques can provide highly accurate structural information. We present new results from the VLBA at 7mm wavelength that for the first time reveal two-dimensional intrinsic structure while also demonstrating the stability of the intrinsic size during periods of significant activity at NIR and X-ray wavelengths.

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Monday Nov 10, 2014
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Sgr A* is one of the few black holes whose capture radius is just resolvable with the

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Monday Nov 10, 2014
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Over the last 20 years, advances in high angular resolution imaging technology has enabled the motions of individual stars to be tracked at the Galactic Center.

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