X-ray burst creates concentric rings – a pulse of radiation from a black hole that makes light echoes from galactic dust clouds visible

Astronomers have captured an astonishing array of concentric rings of X-rays. This light echo was created when clouds of galactic dust smashed into a burst of rays from the black hole V404 Cygni, 7800 years away. The resulting eight beam rings now provide valuable information about the nature and distribution of dust in the Milky Way.

For decades, V404 Cygni’s double system, about 7,800 light-years away, has been quiet and inconspicuous. Inside it, a small star orbits a stellar black hole of about ten solar masses. indeed in June 2015 Suddenly changed: the black hole experienced a series of intense bursts of rays that temporarily made the system the brightest source of X-rays in the sky. At the same time, very short spasms frequently Reddish flashes of light A thousand suns card.

How are rings of rays created?

Astronomers working with Sebastian Heinz of the University of Wisconsin-Madison have deciphered another phenomenon associated with this radiation outbreak. It’s a scattering effect that frames a black hole’s X-rays into stunning rings of radiation. This phenomenon is caused by dust clouds scattered in the Milky Way, which refract and collect radiation on its way to Earth.

“With stationary X-ray sources, this scattering only leads to the formation of a diffuse halo around the radiation source,” Hines and his team explain. “But if the source generates well-defined flares followed by recesses, then the scattered radiation takes the form of separate rings.” The thickness, number, and intensity of radiation rings provide valuable information about the distribution and type of galactic dust.

So Hines and his team reconstructed the shape of V404 Cygni’s radiation rings in detail using data from the Chandra and Swift X-ray observatories.

Eight concentric rings

The result: astronomers have succeeded in showing other light echoes in addition to the four known rays. “We identified a total of eight separate episodes in the Swift photos,” the team reports. It can also be found in fragments in the images of the Chandra X-ray telescope. The brightness of the concentric rings decreases from the inside out. Some inner rings also show bar-like fluctuations in brightness.

The four inner rings are very sharp and clearly defined. “This suggests that highly concentrated dust clouds are responsible for these radiation rings,” the astronomers reported. A slight lateral deflection of some of the rings also indicates that these individual dust clouds are not directly behind each other in line-of-sight to the V404 Cygni.

Information about galactic dust clouds

Through these features combined with the diameter of the X-ray rings, the team was able to determine the approximate location and size of the dust clouds. Accordingly, the X-ray pulses from the outbreak passed through eight different dust clouds on their way to Earth. These are between 6800 and about 3300 light-years away from us and have different densities and sizes. The cloud closest to us is the largest, being about 185 light-years thick, while the smallest is about twelve light-years thick.

X-ray spectra of the rings and additional model analyzes also show that dust clouds consist primarily of graphite and silicate grains. As previously predicted in theoretical models, these grains are not evenly distributed in the clouds. Instead, the dense center of all clouds is shifted toward the galactic plane, Haynes and colleagues report.

This is how galactic dust scatters X-rays from a black hole.© Chandra X-ray Observatory

Taken together, our observations show that a combination of high-resolution Chandra images and low-resolution but more frequent Swift data is a powerful tool for studying the echoes of galactic dust radiation! (Astrophysical Journal, 2021; doi: 10.3847/0004-637X/825/1/15)

Coyle: NASA, Chandra X-ray Observatory

10. August 2021

– Nadia Podebrigar