In a recent moderator's note, I wrote
[[about the Event Horizon Telescope announcement of the first
"picture of a black hole"]]
4. The first 5 research papers describing this are open-access at the
Astrophysical Journal Letters website: (There's mention of a paper 6
but I haven't found it yet)

First M87 Event Horizon Telescope Results.
I. The Shadow of the Supermassive Black Hole
https://iopscience.iop.org/article/1...41-8213/ab0ec7

First M87 Event Horizon Telescope Results.
II. Array and Instrumentation
https://iopscience.iop.org/article/1...41-8213/ab0c96

First M87 Event Horizon Telescope Results.
III. Data Processing and Calibration
https://iopscience.iop.org/article/1...41-8213/ab0c57

First M87 Event Horizon Telescope Results.
IV. Imaging the Central Supermassive
Black Hole
https://iopscience.iop.org/article/1...41-8213/ab0e85

First M87 Event Horizon Telescope Results.
V. Physical Origin of the Asymmetric Ring
https://iopscience.iop.org/article/1...41-8213/ab0f43

paper 6 (also Astrophysical Journal Letters open-access) is at
First M87 Event Horizon Telescope Results.
VI. The Shadow and Mass of the Central Black Hole
https://iopscience.iop.org/article/1...41-8213/ab0f43

and there's a very informative commentary/synopsis of all the results at
Focus on the First Event Horizon Telescope Results
https://iopscience.iop.org/journal/2...e/Focus_on_EHT

ciao,

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"He wakes me up every morning meowing to death because he wants to
go out, and then when I open the door he stays put, undecided, and
then glares at me when I put him out"
-- Nathalie Loiseau (French minister for European Affairs,
explaining why she named her cat "Brexit")