First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration

Kazunori Akiyama , Antxon Alberdi , Walter Alef , Juan Carlos Algaba , Richard Anantua , Keiichi Asada , Rebecca Azulay , Uwe Bach , Anne-Kathrin Baczko , David Ball , Mislav Baloković , John Barrett , Michi Bauböck , Bradford A. Benson , Dan Bintley , Lindy Blackburn , Raymond Blundell , Katherine L. Bouman , Geoffrey C. Bower , Hope Boyce , Michael Bremer , Christiaan D. Brinkerink , Roger Brissenden , Silke Britzen , Avery E. Broderick , Dominique Broguiere , Thomas Bronzwaer , Sandra Bustamante , Do-Young Byun , John E. Carlstrom , Chiara Ceccobello , Andrew Chael , Chi-Kwan Chan , Koushik Chatterjee , Shami Chatterjee , Ming-Tang Chen , Yongjun Chen , Xiaopeng Cheng , Ilje Cho , Pierre Christian , Nicholas S. Conroy , John E. Conway , James M. Cordes , Thomas M. Crawford , Geoffrey B. Crew , Alejandro Cruz-Osorio , Yuzhu Cui , Jordy Davelaar , Mariafelicia de Laurentis , Roger Deane , Jessica Dempsey , Gregory Desvignes (1) , Jason Dexter , Vedant Dhruv , Sheperd S. Doeleman , Sean Dougal , Sergio A. Dzib , Ralph P. Eatough , Razieh Emami , Heino Falcke , Joseph Farah , Vincent L. Fish , Ed Fomalont , H. Alyson Ford , Raquel Fraga-Encinas , William T. Freeman , Per Friberg , Christian M. Fromm , Antonio Fuentes , Peter Galison , Charles F. Gammie , Roberto García , Olivier Gentaz , Boris Georgiev , Ciriaco Goddi , Roman Gold , Arturo I. Gómez-Ruiz , José L. Gómez , Minfeng Gu , Mark Gurwell , Kazuhiro Hada , Daryl Haggard , Kari Haworth , Michael H. Hecht , Ronald Hesper , Dirk Heumann , Luis C. Ho , Paul Ho , Mareki Honma , Chih-Wei L. Huang , Lei Huang , David H. Hughes , Shiro Ikeda , C. M. Violette Impellizzeri , Makoto Inoue , Sara Issaoun , David J. James , Buell T. Jannuzi , Michael Janssen , Britton Jeter , Wu Jiang , Alejandra Jiménez-Rosales , Michael D. Johnson , Svetlana Jorstad , Abhishek V. Joshi , Taehyun Jung , Mansour Karami , Ramesh Karuppusamy , Tomohisa Kawashima , Garrett K. Keating , Mark Kettenis , Dong-Jin Kim , Jae-Young Kim , Jongsoo Kim , Junhan Kim , Motoki Kino , Jun Yi Koay , Prashant Kocherlakota , Yutaro Kofuji , Patrick M. Koch , Shoko Koyama , Carsten Kramer , Michael Kramer , Thomas P. Krichbaum , Cheng-Yu Kuo , Noemi La Bella , Tod R. Lauer , Daeyoung Lee , Sang-Sung Lee , Po Kin Leung , Aviad Levis , Zhiyuan Li , Rocco Lico , Greg Lindahl , Michael Lindqvist , Mikhail Lisakov , Jun Liu , Kuo Liu , Elisabetta Liuzzo , Wen-Ping Lo , Andrei P. Lobanov , Laurent Loinard , Colin J. Lonsdale , Ru-Sen Lu , Jirong Mao , Nicola Marchili , Sera Markoff , Daniel P. Marrone , Alan P. Marscher , Iván Martí-Vidal , Satoki Matsushita , Lynn D. Matthews , Lia Medeiros , Karl M. Menten , Daniel Michalik , Izumi Mizuno , Yosuke Mizuno , James M. Moran , Kotaro Moriyama , Monika Moscibrodzka , Cornelia Müller , Alejandro Mus , Gibwa Musoke , Ioannis Myserlis , Andrew Nadolski , Hiroshi Nagai , Neil M. Nagar , Masanori Nakamura , Ramesh Narayan , Gopal Narayanan , Iniyan Natarajan , Antonios Nathanail , Santiago Navarro Fuentes , Joey Neilsen , Roberto Neri , Chunchong Ni , Aristeidis Noutsos , Michael A. Nowak , Junghwan Oh , Hiroki Okino , Héctor Olivares , Gisela N. Ortiz-León , Tomoaki Oyama , Feryal Özel , Daniel C. M. Palumbo , Georgios Filippos Paraschos , Jongho Park , Harriet Parsons , Nimesh Patel , Ue-Li Pen , Dominic W. Pesce , Vincent Piétu , Richard Plambeck , Aleksandar Popstefanija , Oliver Porth , Felix M. Pötzl , Ben Prather , Jorge A. Preciado-López , Dimitrios Psaltis , Hung-Yi Pu , Venkatessh Ramakrishnan , Ramprasad Rao , Mark G. Rawlings , Alexander W. Raymond , Luciano Rezzolla , Angelo Ricarte , Bart Ripperda , Freek Roelofs , Alan Rogers , Eduardo Ros , Cristina Romero-Cañizales , Arash Roshanineshat , Helge Rottmann , Alan L. Roy , Ignacio Ruiz , Chet Ruszczyk , Kazi L. J. Rygl , Salvador Sánchez , David Sánchez-Argüelles , Miguel Sánchez-Portal , Mahito Sasada , Kaushik Satapathy , Tuomas Savolainen , F. Peter Schloerb , Jonathan Schonfeld , Karl-Friedrich Schuster , Lijing Shao , Zhiqiang Shen , Des Small , Bong Won Sohn , Jason Soohoo , Kamal Souccar , He Sun , Fumie Tazaki , Alexandra J. Tetarenko , Paul Tiede , Remo P. J. Tilanus , Michael Titus , Pablo Torne , Efthalia Traianou , Tyler Trent , Sascha Trippe , Matthew Turk , Ilse van Bemmel , Huib Jan van Langevelde , Daniel R. van Rossum , Jesse Vos , Jan Wagner , Derek Ward-Thompson , John Wardle , Jonathan Weintroub , Norbert Wex , Robert Wharton , Maciek Wielgus , Kaj Wiik , Gunther Witzel , Michael F. Wondrak , George N. Wong , Qingwen Wu , Paul Yamaguchi , Doosoo Yoon , André Young , Ken Young , Ziri Younsi , Feng Yuan , Ye-Fei Yuan , J. Anton Zensus , Shuo Zhang , Guang-Yao Zhao , Shan-Shan Zhao , Claudio Agurto , Juan Pablo Araneda , Oriel Arriagada , Alessandra Bertarini , Ryan Berthold , Jay Blanchard , Ken Brown , Mauricio Cárdenas , Michael Cantzler , Patricio Caro , Tim C. Chuter , Miroslaw Ciechanowicz , Iain M. Coulson , Joseph Crowley , Nathalie Degenaar , Sven Dornbusch , Carlos A. Durán , Karl Forster , Gertie Geertsema , Edouard González , Dave Graham , Frédéric Gueth , Chih-Chiang Han , Cristian Herrera , Ruben Herrero-Illana , Stefan Heyminck , James Hoge , Yau-De Huang , Homin Jiang , David John , Thomas Klein , Derek Kubo , John Kuroda , Caleb Kwon , Robert Laing , Ching-Tang Liu , Kuan-Yu Liu , Felipe Mac-Auliffe , Pierre Martin-Cocher , Callie Matulonis , Hugo Messias , Zheng Meyer-Zhao , Francisco Montenegro-Montes , William Montgomerie , Dirk Muders , Hiroaki Nishioka , Timothy J. Norton , Rodrigo Olivares , Juan Pablo Pérez-Beaupuits , Rodrigo Parra , Michael Poirier , Nicolas Pradel , Philippe A. Raffin , Jorge Ramírez , Mark Reynolds , Alejandro F. Saez-Madain , Jorge Santana , Kevin M. Silva , Don Sousa , William Stahm , Karl Torstensson , Paulina Venegas , Craig Walther , Gundolf Wieching , Rudy Wijnands , Jan G. A. Wouterloot

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ~50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.

Mots clés: Black holes

Domaines: Planète et Univers [physics]; Astrophysique [astro-ph]

Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, et al.. First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration. The Astrophysical journal letters, 2022, 930, ⟨10.3847/2041-8213/ac6675⟩. ⟨insu-03713316⟩