Astronomers have studied the X-ray echo of black holes in the Milky Way

(ORDO NEWS) — Scientists have described how the surroundings of a black hole change in the process of absorbing matter from a neighboring star.

It turned out that the corona of the hole expands briefly during the final ejection of high-energy particles. And this may explain the influence of outbursts of supermassive black holes on the evolution of the galaxies surrounding them.

Studying black holes is not an easy task, because these deep “wells” in the fabric of space-time attract even particles of light. But during the absorption of matter, black holes sometimes flare up with X-ray radiation, which is reflected from the matter falling into the hole and briefly illuminates the surrounding space.

By studying “X-ray echoes” in eight systems, a team of astronomers at the Massachusetts Institute of Technology have been able to describe the neighborhoods of black holes.

The study began with the search for suitable objects. The team developed an algorithm that walked through observations from NICER , a high-resolution X-ray telescope aboard the ISS.

The algorithm found 26 black hole binaries that had previously flared with X-rays. From these, the team selected ten systems that were suitable in terms of brightness and distance for further X-ray echo analysis.

After analyzing the signals, the scientists divided the systems into groups with similar delays between two types of X-ray radiation: coming from the corona and reflected from the accretion disk.

This delay can be used to estimate the distance between them. By comparing X-ray echoes at different stages of the flare, the scientists were able to assess how the corona changes and how the disk moves.

The corona of a black hole is a region of high-energy plasma near the event horizon. Scientists have found that during the absorption of matter, it changes the most. The two states through which the object passes in this case are called “hard” and “soft” by physicists.

First, the hole enters a “hard” state, in which delays last for milliseconds: a corona saturated with high-energy photons flashes, and a relatively weak uniform stream of particles flies out. This state lasts for several weeks.

Then, in a few days, the hole flares for the last time and goes into a “soft” low-energy state. During this period, the signal delay increases for a short time, that is, the distance between the corona and the disk increases.

It is likely that the corona expands significantly and stretches upward relative to the hole. At the same time, a huge and powerful jet of high-energy particles escapes from the pole, and the uniform flow fades.

The described process will help to understand how supermassive black holes in the centers of galaxies are able to throw particles into intergalactic space over vast distances.

Tens of millions of relatively small black holes fly in the stellar systems of our Galaxy. “The role of these black holes in the evolution of the Galaxy remains an open question in modern astrophysics,” commented Erin Kara , one of the authors of the new work.

“Remarkably, the black holes in these binary systems behave like miniature supermassive black holes. So by studying outbursts in small neighboring systems, we can understand how similar outbursts from supermassive black holes affect their surrounding galaxies.”


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