In the first, astronomers see the corona of a black hole disappear, then appear

There seems to be a strange sense of humor in the universe. While a crown-enclosed virus has gone rough around the world, the corona, which is completely isolated about 100 million light years from Earth, has mysteriously disappeared.

For the first time, astronomers at MIT and elsewhere saw as their corona a supermassive black hole, the ultrabright, billion-degree ring of high-energy particles encircling the event horizon of a black hole, was suddenly destroyed.

The reason for this dramatic change is not clear, although researchers speculate that the source of the disaster may have been the star caught in the gravitational pull of the black hole. Like throwing a pebble into a gearbox, the star may have recirculated through a disk of black hole’s rotating material, causing the corona’s high-energy particles to suddenly submerge everything nearby.

As a result, astronomers observed, within just one year, there was an initial and surprising drop in the brightness of the black hole by a factor of 10,000.

“We expect this major change to change over several thousands to millions of years in time,” says Erin Kara, assistant professor of physics at MIT. “But in this item, we replaced it with 10,000 in a year, and it also changed by a factor of 100 in eight hours, which is completely unheard of and is really mind-boggling.”

After the disappearance of the corona, astronomers continued to observe that the black hole began to slowly pull together material from its outer edges to improve its rotating accretion disk, allowing the black-hole’s event horizon High-energy X-rays began to spin around. . In this way, in just a few months, the black hole was able to generate a new corona, almost to its original brightness.

“This seems to be the first time we’ve ever seen a corona disappear first, but then recreate itself, and we’re seeing it in real time,” Kara says. “It will be really important to understand how the corona of a black hole is heated and operated in the first place.”

Kara and her co-authors, including lead author Claudio Ricci of Universidad Diego Portals in Santiago, Chile, have published their findings today Astrophysical Journal Letters. MIT co-authors include Ron Remillard, and Dheeraj Pasam.

A Spry Washing Machine

In March 2018, there was an unexpected explosion of the all-sky automated survey ASSASN for Super-Nova, which surveys the entire night sky for supernova activity. The survey recorded 1ES 1927 + 654, a flash from an active galactic nucleus or AGN, a type of supermassive black hole with high-to-normal brightness at the center of a galaxy. ASSASN found that the object’s brightness was about 40 times greater than its normal brightness.

“It was an AGN we knew about, but it wasn’t very special,” Kara says. “They then noticed that this run-of-the-mill AGN suddenly brightened, which caught our attention, and we started pointing to a lot of other telescopes of other wavelengths to see it.”

The team used several telescopes to observe black holes in X-ray, optical, and ultraviolet wave bands. Most of these telescopes were periodically pointed into black holes, for example, observations are recorded for a full day every six months. The team looked at the black hole daily with NASA’s NICER, a very small X-ray telescope that was mounted on the International Space Station, with detectors developed and built by researchers at MIT.

“NICER is great because it’s very agile,” Kara says. “It is a small washing machine bouncing around the ISS, and it can collect a ton of X-ray photons. Every day, NICER can take a short look at this AGN, then go out and do something else. “

With frequent observations, researchers were able to catch the black hole as it dropped rapidly in brightness, virtually all the wave bands they measured, and especially in the high-energy X-ray band – an observation that would indicate The corona of the black hole had completely and suddenly evaporated.

Kara recalls, “After ASSASN left we went through this huge mad attack, we saw the disappearance of Corona.” “It became undesirable, something we had never seen before.”

A jerk flash

Physicists figure out exactly what causes the corona to form, but they believe it has nothing to do with the configuration of the magnetic field lines that run through the accretion disk of the black hole. In the outer regions of a disk rotating around the contents of a black hole, the magnetic field lines are more or less in a straight configuration. Near and especially near the event horizon, reconcile material circles with more energy, in a way that can cause magnetic field lines to bend and break. This entanglement of magnetic energy can spin particles moving close to the black hole to the level of high-energy X-rays, forming a corona like crown that surrounds the black hole.

Kara and her co-workers believe that if a wayward star was in fact the culprit for Corona’s disappearance, it would first be separated from the black hole’s gravitational bridge, scattering the stellar debris into the acceleration disk. This may be the cause of the temporary flash in brightness that ASSASN has captured. This “tide-reflux disruption”, as astronomers called such a shocking event, would have triggered a lot of material in the disk to suddenly collapse into a black hole. This may have thrown out the magnetic field lines of the disc in such a way that it can no longer generate and support high-energy corona.

This last point is a potentially important one for understanding how the coronus is first formed. Depending on the mass of a black hole, there is a fixed radius within which a star will certainly be drawn by the gravity of a black hole.

“Which tells us that if all the action is taking place within that tidal range, it means that the magnetic field configuration that the corona is supporting must be within that scope,” says Kara. “This means that for any normal corona, the magnetic fields within that radius are responsible for forming a corona.”

Researchers calculated that if indeed a star was the cause of the missing corona of a black hole, and if a corona formed into a supermassive black hole of similar size, it would do so within a radius of about 4 light minutes – a distance of the black hole. About 75 million kilometers have been translated from the center.

“With the event that the event was caused by the disintegration of a stellar tide, these would be some of the most difficult obstacles where the corona should be present,” says Kara.

Corona highlighted in high-energy X-rays since the reform, which the team was also able to see. It is not as bright as it once was, but researchers have continued to monitor it, albeit less frequently, to see what is more in this system.

“We want to keep an eye on it,” Kara says. “It’s still in this unusual high flow state, and maybe it will drive something crazy again, so we don’t want to miss it.”

This research was funded, in part, by NASA.