Spatially resolved polarization swings in the supermassive binary black hole candidate OJ 287 with first Event Horizon Telescope observations
Journal article, 2026
We present the first Event Horizon Telescope 1.3 mm observations of the supermassive binary black hole candidate OJ 287. The observations achieved an unprecedented angular resolution of 18 µas and reveal significant structural and polarization variability over just five days, marking the shortest timescale on which such changes have been directly imaged in this source. The inner jet exhibits a twisted ridgeline structure, with features displaying apparent superluminal motions up to about 22 c. The linear polarization maps reveal three main polarized features whose electric-vector position angles (EVPAs) change substantially over the time span of our observations, including a component with a radial polarization consistent with being produced by a recollimation shock. Most notably, we directly resolved two innermost jet components whose EVPAs rotate in opposite directions. The faster component, moving at 2.4 ± 0.9 µas/day (17.4 ± 6.5 c), exhibits counterclockwise EVPA swings of roughly 3.7◦ per day, while the slower component, with a proper motion of 1.4 ± 0.3 µas/day (10.2 ± 2.2 c), rotates clockwise at approximately 2.5◦ per day. Previous studies inferred helical magnetic fields in AGN jets from time-resolved or integrated polarization variability but lacked the angular resolution to directly image this effect. Our results provide spatially resolved evidence that a helical magnetic field threads the jet’s collimation and acceleration zone, ruling out models based on the superposition of unresolved components. Our analysis suggests that propagating shocks interact with a Kelvin-Helmholtz plasma instability, illuminating different phases of the helical magnetic field and producing the observed polarization spatial and temporal variability. Moreover, our model naturally accounts for the more rapid polarization rotation observed in the faster moving component. Our model predicts even more rapid swings in polarization, which could be tested with future observations featuring a more densely sampled time coverage.
instabilities
techniques: interferometric
galaxies: active
black hole physics
galaxies: individual: OJ 287
radiation mechanisms: non-thermal
Author
J. L. Gomez
Spanish National Research Council (CSIC)
I. Cho
Spanish National Research Council (CSIC)
E. Traianou
Spanish National Research Council (CSIC)
T.P. Krichbaum
Max Planck Society
G. Y. Zhao
Spanish National Research Council (CSIC)
R. Lico
Spanish National Research Council (CSIC)
Antonio Fuentes
Spanish National Research Council (CSIC)
Marianna Foschi
Spanish National Research Council (CSIC)
Rohan Dahale
Spanish National Research Council (CSIC)
Boris Georgiev
University of Arizona
Kotaro Moriyama
Goethe University Frankfurt
M. Wielgus
Spanish National Research Council (CSIC)
R. Gold
Heidelberg University
Dominic W. Pesce
Harvard University
Hendrik Müller
Max Planck Society
S.G. Jorstad
Boston University
Teresa Toscano
Spanish National Research Council (CSIC)
J. Röder
Spanish National Research Council (CSIC)
José M. Martí
Universitat de Valencia
M. Perucho
Universitat de Valencia
Yuri Y. Kovalev
Max Planck Society
S. Komossa
Max Planck Society
Achamveedu Gopakumar
Tata Institute of Fundamental Research
M. J. Valtonen
Tuorla Observatory
Gabriele Bruni
Istituto nazionale di astrofisica (INAF)
S. Chandra
Physical Research Laboratory
Kazunori Akiyama
Massachusetts Institute of Technology (MIT)
E. Albentosa-Ruiz
Universitat de Valencia
Antxon Alberdi
Spanish National Research Council (CSIC)
Walter Alef
Max Planck Society
Juan-Carlos Algaba
University of Malaya
Richard Anantua
Harvard University
K. Asada
Academia Sinica
R. Azulay
Max Planck Society
U. Bach
Max Planck Society
A. K. Baczko
Max Planck Society
David Ball
University of Arizona
Mislav Baloković
Yale University
Bidisha Bandyopadhyay
University of Concepcion
John Barrett
Massachusetts Institute of Technology (MIT)
M. Bauböck
Grainger College of Engineering
Bradford A. Benson
Fermi National Accelerator Laboratory
Dan Bintley
East Asian Observatory
Lindy Blackburn
Harvard University
R. Blundell
Harvard-Smithsonian Center for Astrophysics
K. L. Bouman
California Institute of Technology (Caltech)
G. C. Bower
East Asian Observatory
M. Bremer
Institut de Radioastronomie Millimétrique (IRAM)
Roger Brissenden
Harvard University
Silke Britzen
Max Planck Society
Avery E. Broderick
Perimeter Institute for Theoretical Physics
D. Broguière
Institut de Radioastronomie Millimétrique (IRAM)
Thomas Bronzwaer
Radboud University
Sandra Bustamente
University of Massachusetts
Douglas Ferreira Carlos
University of Sao Paulo (USP)
J. E. Carlstrom
University of Chicago
A. Chael
Princeton University
Chi Kwan Chan
University of Arizona
Dominic O. Chang
Harvard University
Koushik Chatterjee
Harvard University
S. Chatterjee
Cornell University
Ming Tang Chen
Academia Sinica
Yongjun Chen
Chinese Academy of Sciences
X. P. Cheng
Korea Astronomy and Space Science Institute
Pierre Christian
WattTime
Nicholas S. Conroy
Harvard-Smithsonian Center for Astrophysics
John Conway
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Thomas M. Crawford
University of Chicago
G. Crew
Massachusetts Institute of Technology (MIT)
Alejandro Cruz-Osorio
Universidad Nacional Autónoma de México
Yuzhu Cui
Huazhong Normal University
Brandon Curd
Harvard University
Jordy Davelaar
Princeton University
Mariafelicia De Laurentis
University of Naples Federico II
R. P. Deane
University of Witwatersrand
Jessica Dempsey
East Asian Observatory
Gregory Desvignes
Max Planck Society
Jason Dexter
JILA
Vedant Dhruv
Grainger College of Engineering
Indu K. Dihingia
Shanghai Jiao Tong University
S. Doeleman
Harvard University
Sergio A. Dzib
Max Planck Society
Ralph P. Eatough
Max Planck Society
Joseph R. Farah
Las Cumbres Observatory Global Telescope Network
V. Fish
Massachusetts Institute of Technology (MIT)
E. Fomalont
National Radio Astronomy Observatory
H.D. Falcke
University of Arizona
H.D. Falcke
Radboud University
R. Fraga-Encinas
Radboud University
William T. Freeman
Massachusetts Institute of Technology (MIT)
P. Friberg
East Asian Observatory
Christian M. Fromm
Max Planck Society
Peter Galison
Harvard University
Charles F. Gammie
Grainger College of Engineering
Roberto Garcia
Institut de Radioastronomie Millimétrique (IRAM)
Olivier Gentaz
Institut de Radioastronomie Millimétrique (IRAM)
Gertie Geertsema
Royal Netherlands Meteorological Institute
C. Goddi
University of Sao Paulo (USP)
Arturo I. Gómez-Ruiz
National Institute of Astrophysics, Optics and Electronics
Minfeng Gu
Chinese Academy of Sciences
K. Hada
University of Tokyo
Daryl Haggard
McGill University
R. Hesper
University of Groningen
Dirk Heumann
University of Arizona
Luis C. Ho
Beijing University of Technology
P. T. P. Ho
Academia Sinica
Mareki Honma
National Astronomical Observatory of Japan
Chih Wei L. Huang
Academia Sinica
Lei Huang
Chinese Academy of Sciences
D. Hughes
National Institute of Astrophysics, Optics and Electronics
Shiro Ikeda
National Astronomical Observatory of Japan
C. M. V. Impellizzeri
National Radio Astronomy Observatory
Makoto Inoue
Academia Sinica
S. Issaoun
Harvard-Smithsonian Center for Astrophysics
David J. James
ASTRAVEO
Buell T. Jannuzi
University of Arizona
Michael Janssen
Max Planck Society
Britton Jeter
Academia Sinica
Wu Jiang
Chinese Academy of Sciences
Alejandra Jimenez-Rosales
Radboud University
Michael D. Johnson
Harvard University
Adam C. Jones
University of Chicago
Abhishek V. Joshi
Grainger College of Engineering
Taehyun Jung
Korea Astronomy and Space Science Institute
R. Karuppusamy
Max Planck Society
Tomohisa Kawashima
University of Tokyo
G. Keating
Harvard-Smithsonian Center for Astrophysics
M. M. Kettenis
Joint Institute for VLBI in Europe (JIVE)
Dong-Jin Kim
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Jae-Young Kim
Max Planck Society
Jongsoo Kim
Korea Astronomy and Space Science Institute
M. Kino
National Astronomical Observatory of Japan
Jun Yi Koay
Academia Sinica
Prashant Kocherlakota
Goethe University Frankfurt
Yutaro Kofuji
National Astronomical Observatory of Japan
Patrick M. Koch
Academia Sinica
Shoko Koyama
Academia Sinica
C. Kramer
Institut de Radioastronomie Millimétrique (IRAM)
Joana A. Kramer
Max Planck Society
Junhan Kim
Max Planck Society
Junhan Kim
Korea Advanced Institute of Science and Technology (KAIST)
Sang Sung Lee
Korea Astronomy and Space Science Institute
Aviad Levis
California Institute of Technology (Caltech)
Zhiyuan Li
Nanjing University
Greg Lindahl
Academia Sinica
Greg Lindahl
Common Crawl Foundation
Michael Lindqvist
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Mikhail Lisakov
Pontificia Universidad Católica de Valparaíso
Jun Liu
Max Planck Society
Kuo Liu
Chinese Academy of Sciences
Elisabetta Liuzzo
Istituto di Radioastronomia
Wen-Ping Lo
Academia Sinica
A. P. Lobanov
Max Planck Society
L. Loinard
Harvard University
Colin Lonsdale
Massachusetts Institute of Technology (MIT)
Amy E. Lowitz
University of Arizona
R.S. Lu
Max Planck Society
N. R. Macdonald
Max Planck Society
Jirong Mao
Yunnan Observatories
Nicola Marchili
Max Planck Society
S. Markoff
Anton Pannekoek Institute for Astronomy
D. P. Marrone
University of Arizona
A. Marscher
Boston University
Ivan Marti-Vidal
Universitat de Valencia
S. Matsushita
Academia Sinica
Lynn D. Matthews
Massachusetts Institute of Technology (MIT)
Lia Medeiros
Princeton University
K. Menten
Max Planck Society
Izumi Mizuno
East Asian Observatory
Yosuke Mizuno
Goethe University Frankfurt
Joshua Montgomery
University of Chicago
James M. Moran
Harvard University
M. Mościbrodzka
Radboud University
Wanga Mulaudzi
Anton Pannekoek Institute for Astronomy
C. Müller
Max Planck Society
A. Mus
University of Cagliari
Gibwa Musoke
Radboud University
I. Myserlis
Institut de Radioastronomie Millimétrique (IRAM)
H. Nagai
National Astronomical Observatory of Japan
N. M. Nagar
University of Concepcion
Dhanya G. Nair
Max Planck Society
Masanori Nakamura
Academia Sinica
Gopal Narayanan
University of Massachusetts
Iniyan Natarajan
Harvard University
Antonios Nathanail
Goethe University Frankfurt
Santiago Navarro Fuentes
Institut de Radioastronomie Millimétrique (IRAM)
Joseph Neilsen
Villanova University
Chunchong Ni
Perimeter Institute for Theoretical Physics
Michael A. Nowak
Washington University in St. Louis
Junghwan Oh
Joint Institute for VLBI in Europe (JIVE)
Hiroki Okino
National Astronomical Observatory of Japan
Héctor Olivares
Centre For Research And Development In Mathematics And Applications (CIDMA)
Tomoaki Oyama
National Astronomical Observatory of Japan
Feryal Özel
Georgia Institute of Technology
Daniel C.M. Palumbo
Harvard University
Georgios Filippos Paraschos
Max Planck Society
Jongho Park
Academia Sinica
Harriet Parsons
East Asian Observatory
N. Patel
Harvard-Smithsonian Center for Astrophysics
U. L. Pen
Academia Sinica
Vincent Piétu
Institut de Radioastronomie Millimétrique (IRAM)
Aleksandar PopStefanija
University of Massachusetts
Oliver Porth
Goethe University Frankfurt
Ben Prather
Grainger College of Engineering
G. Principe
Istituto di Radioastronomia
Dimitrios Psaltis
Georgia Institute of Technology
Hung-Yi Pu
Academia Sinica
Venkatessh Ramakrishnan
University of Concepcion
R. Rao
Harvard-Smithsonian Center for Astrophysics
M.G. Rawlings
East Asian Observatory
Luciano Rezzolla
Goethe University Frankfurt
Angelo Ricarte
Harvard University
Bart Ripperda
Perimeter Institute for Theoretical Physics
Freek Roelofs
Radboud University
C. Romero-Cañizales
Academia Sinica
Eduardo Ros
Max Planck Society
Arash Roshanineshat
University of Arizona
H. Rottmann
Max Planck Society
A. Roy
Max Planck Society
Ignacio Ruiz
Institut de Radioastronomie Millimétrique (IRAM)
C. Ruszczyk
Massachusetts Institute of Technology (MIT)
Kazi L.J. Rygl
Istituto di Radioastronomia
S. Sanchez
Institut de Radioastronomie Millimétrique (IRAM)
David Sánchez-Arguelles
National Institute of Astrophysics, Optics and Electronics
M. Sánchez Portal
Institut de Radioastronomie Millimétrique (IRAM)
Mahito Sasada
National Astronomical Observatory of Japan
Kaushik Satapathy
University of Arizona
Saurabh
Max Planck Society
T. Savolainen
Max Planck Society
F. P. Schloerb
University of Massachusetts
Jonathan Schonfeld
Harvard-Smithsonian Center for Astrophysics
K. Schuster
Institut de Radioastronomie Millimétrique (IRAM)
Lijing Shao
Max Planck Society
Zhi Qiang Shen
Chinese Academy of Sciences
Sasikumar Silpa
University of Concepcion
Des Small
Joint Institute for VLBI in Europe (JIVE)
B. W. Sohn
Korea Astronomy and Space Science Institute
J. SooHoo
Massachusetts Institute of Technology (MIT)
León David Sosapanta Salas
Anton Pannekoek Institute for Astronomy
Kamal Souccar
University of Massachusetts
Joshua S. Stanway
University of Central Lancashire
He Sun
Beijing University of Technology
Fumie Tazaki
Tokyo Electron Technology Solutions Limited
Alexandra J. Tetarenko
University of Lethbridge
Paul Tiede
Harvard University
R. P. J. Tilanus
University of Arizona
M. Titus
Massachusetts Institute of Technology (MIT)
Kenji Toma
Tohoku University
Pablo Torne
Max Planck Society
Tyler Trent
University of Arizona
S. Trippe
Seoul National University
Matthew Turk
University of Illinois
I. van Bemmel
Netherlands Institute for Radio Astronomy (ASTRON)
H. J. van Langevelde
Leiden University
Daniel R. van Rossum
Radboud University
Jesse Vos
Radboud University
Jan Wagner
Max Planck Society
D. Ward-Thompson
University of Central Lancashire
John Wardle
Brandeis University
Jasmin E. Washington
University of Arizona
J. Weintroub
Harvard University
Robert Wharton
Max Planck Society
K. Wiik
University of Turku
Gunther Witzel
Max Planck Society
Michael F. Wondrak
Radboud University
George N. Wong
Princeton University
Qingwen Wu
Huazhong University of Science and Technology
Nitika Yadlapalli
California Institute of Technology (Caltech)
Paul Yamaguchi
Harvard-Smithsonian Center for Astrophysics
Aristomenis Yfantis
Radboud University
Doosoo Yoon
Anton Pannekoek Institute for Astronomy
A. Young
Radboud University
Ziri Younsi
Goethe University Frankfurt
Wei Yu
Harvard-Smithsonian Center for Astrophysics
Feng Yuan
Fudan University
Ye-Fei Yuan
University of Science and Technology of China
Ai Ling Zeng
Spanish National Research Council (CSIC)
A.J. Zensus
Max Planck Society
Shuo Zhang
Michigan State University
Shan-Shan Zhao
Chinese Academy of Sciences
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 705 A23Onsala space observatory infrastructure
Swedish Research Council (VR) (2017-00648), 2018-01-01 -- 2021-12-31.
RadioNet 4
European Commission (EC) (EC/H2020/730562), 2017-01-01 -- 2020-12-31.
Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202555831