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Office of Scientific and Technical Information
 

Horizon-scale variability of from 2017--2021 EHT observations

Journal Article · · Astronomy and Astrophysics
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  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); National Astronomical Observatory of Japan (NAOJ), Tokyo (Japan); Harvard Univ., Cambridge, MA (United States); Event Horizon Telescope (EHT) Collaboration. et al.
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Here, we report three epochs of polarized images of M87* at 230 GHz using data from the Event Horizon Telescope (EHT) taken in 2017, 2018, and 2021. The baseline coverage of the 2021 observations is significantly improved through the addition of two new EHT stations: the 12 m Kitt Peak Telescope and the Northern Extended Millimetre Array (NOEMA). All observations result in images dominated by a bright, asymmetric ring with a persistent diameter of 43.9 ± 0.6 µas, consistent with expectations for lensed synchrotron emission encircling the apparent shadow of a supermassive black hole. We find that the total intensity and linear polarization of M87* vary significantly across the three epochs. Specifically, the azimuthal brightness distribution of the total intensity images varies from year to year, as expected for a stochastic accretion flow. However, despite a gamma-ray flare erupting in M87 quasi-contemporaneously to the 2018 observations, the 2018 and 2021 images look remarkably similar. The resolved linear polarization fractions in 2018 and 2021 peak at ∼5%, compared to ∼15% in 2017. The spiral polarization pattern on the ring also varies from year to year, including a change in the electric vector position angle helicity in 2021 that could reflect changes in the magnetized accretion flow or an external Faraday screen. The improved 2021 coverage also provides the first EHT constraints on jet emission outside the ring, on scales of ≲ 1 mas. Overall, these observations provide strong proof of the reliability of the EHT images and probe the dynamic properties of the horizon-scale accretion flow surrounding M87*.
Research Organization:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), High Energy Physics (HEP); USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
89243024CSC000002; 89233218CNA000001; AC05-00OR22725
OSTI ID:
2998878
Report Number(s):
FERMILAB-PUB--25-0735-PPD; oai:inspirehep.net:2974630; arXiv:2509.24593
Journal Information:
Astronomy and Astrophysics, Journal Name: Astronomy and Astrophysics; ISSN 1432-0746; ISSN 0004-6361
Publisher:
EDP SciencesCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

accretion
accretion disks
black hole physics
galaxies: active
galaxies: individual: M87*
galaxies: jets
gravitation