%0 Electronic Article %A Fish, Vincent L. and Johnson, Michael D. and Doeleman, Sheperd S. and Broderick, Avery E. and Psaltis, Dimitrios and Lu, Ru-Sen and Akiyama, Kazunori and Alef, Walter and Algaba, Juan Carlos and Asada, Keiichi and Beaudoin, Christopher and Bertarini, Alessandra and Blackburn, Lindy and Blundell, Ray and Bower, Geoffrey C. and Brinkerink, Christiaan and Cappallo, Roger and Chael, Andrew A. and Chamberlin, Richard and Chan, Chi-Kwan and Crew, Geoffrey B. and Dexter, Jason and Dexter, Matt and Dzib, Sergio A. and Falcke, Heino and Freund, Robert and Friberg, Per and Greer, Christopher H. and Gurwell, Mark A. and Ho, Paul T. P. and Honma, Mareki and Inoue, Makoto and Johannsen, Tim and Kim, Junhan and Krichbaum, Thomas P. and Lamb, James and León-Tavares, Jonathan and Loeb, Abraham and Loinard, Laurent and MacMahon, David and Marrone, Daniel P. and Moran, James M. and Mościbrodzka, Monika and Ortiz-León, Gisela N. and Oyama, Tomoaki and Özel, Feryal and Plambeck, Richard L. and Pradel, Nicolas and Primiani, Rurik A. and Rogers, Alan E. E. and Rosenfeld, Katherine and Rottmann, Helge and Roy, Alan L. and Ruszczyk, Chester and Smythe, Daniel L. and SooHoo, Jason and Spilker, Justin and Stone, Jordan and Strittmatter, Peter and Tilanus, Remo P. J. and Titus, Michael and Vertatschitsch, Laura and Wagner, Jan and Wardle, John F. C. and Weintroub, Jonathan and Woody, David and Wright, Melvyn and Yamaguchi, Paul and Young, André and Young, Ken H. and Zensus, J. Anton and Ziurys, Lucy M. %I American Astronomical Society %D 2016 %D 2016 %G Undetermined %@ 0004-637X %@ 1538-4357 %~ Katalog UB TU-Chemnitz %T PERSISTENT ASYMMETRIC STRUCTURE OF SAGITTARIUS A* ON EVENT HORIZON SCALES %V 820 %J The Astrophysical Journal %V 820 %N 2 %P 90 %U http://dx.doi.org/10.3847/0004-637x/820/2/90 %X ABSTRACT 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 angular scales comparable to that of the general relativistic shadow. Previous EHT observations have used visibility amplitudes to infer the morphology of the millimeter-wavelength emission. Potentially much richer source information is contained in the phases. We report on 1.3 mm phase information on Sgr A* obtained with the EHT on a total of 13 observing nights over four years. Closure phases, which are the sum of visibility phases along a closed triangle of interferometer baselines, are used because they are robust against phase corruptions introduced by instrumentation and the rapidly variable atmosphere. The median closure phase on a triangle including telescopes in California, Hawaii, and Arizona is nonzero. This result conclusively demonstrates that the millimeter emission is asymmetric on scales of a few Schwarzschild radii and can be used to break 180° rotational ambiguities inherent from amplitude data alone. The stability of the sign of the closure phase over most observing nights indicates persistent asymmetry in the image of Sgr A* that is not obscured by refraction due to interstellar electrons along the line of sight. %Z https://katalog.bibliothek.tu-chemnitz.de/Record/ai-49-aHR0cDovL2R4LmRvaS5vcmcvMTAuMzg0Ny8wMDA0LTYzN3gvODIwLzIvOTA %U https://katalog.bibliothek.tu-chemnitz.de/Record/ai-49-aHR0cDovL2R4LmRvaS5vcmcvMTAuMzg0Ny8wMDA0LTYzN3gvODIwLzIvOTA