• DOI:10.1088/0004-637X/807/2/150
• Corpus ID: 50953437

230 GHz VLBI OBSERVATIONS OF M87: EVENT‐HORIZON‐SCALE STRUCTURE DURING AN ENHANCED VERY‐HIGH‐ENERGY γ ?> ‐RAY STATE IN 2012

@article{Akiyama2015230GV,
  title={230 GHz VLBI OBSERVATIONS OF M87: EVENT‐HORIZON‐SCALE STRUCTURE DURING AN ENHANCED VERY‐HIGH‐ENERGY $\gamma$ ?> ‐RAY STATE IN 2012},
  author={Kazunori Akiyama and Ru-Sen Lu and Vincent L. Fish and Sheperd S. Doeleman and Avery E. Broderick and Jason Dexter and Kazuhiro Hada and Motoki Kino and Hiroshi Nagai and Mareki Honma and Michael D. Johnson and Juan Carlos Algaba and Keiichi Asada and Christiaan D. Brinkerink and Raymond Blundell and Geoffrey C. Bower and Roger J. Cappallo and Geoffrey B. Crew and Matt Dexter and Sergio A. Dzib and Robert W. Freund and Per Friberg and Mark A. Gurwell and Paul T. P. Ho and Makoto Inoue and Thomas P. Krichbaum and Laurent Loinard and David Macmahon and Daniel P. Marrone and James M. Moran and Masanori Nakamura and Neil M. Nagar and Gisela N. Ortiz-L{\'e}on and Richard L. Plambeck and Nicolas Pradel and Rurik A. Primiani and Alan E. E. Rogers and Alan L. Roy and Jason SooHoo and J. Le'on Tavares and Remo P. J. Tilanus and Michael Titus and Jan Wagner and Jonathan Weintroub and Paul Yamaguchi and K. H. Young and Anton Zensus and Lucy M Ziurys},
  journal={The Astrophysical Journal},
  year={2015},
  volume={807}
}

• K. Akiyama, R. Lu, +45 authors L. Ziurys
• Published 13 May 2015
• Physics
• The Astrophysical Journal

We report on 230 GHz (1.3 mm) very long baseline interferometry (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. For the first time, we have acquired 230 GHz VLBI interferometric phase information on M87 through measurement of the closure phase on the triangle of long baselines. Most of the measured closure phases are consistent with 0° as expected by physically motivated models for 230 GHz structure such as jet models and accretion disk models. The brightness temperature of the event-horizon-scale structure is ∼ 1 × 10 10 ?> K derived from the compact flux density of ∼1 Jy and the angular size of ∼40 &mgr; as ?> ∼ 5.5 R s ?> , which is broadly consistent with the peak brightness of the radio cores at 1–86 GHz located within ∼ 10 2 ?> R s ?> . Our observations occurred in the middle of an enhancement in very-high-energy (VHE) γ ?> -ray flux, presumably originating in the vicinity of the central black hole. Our measurements, combined with results of multi-wavelength observations, favor a scenario in which the VHE region has an extended size of ∼20–60 R s ?> .