Eddie Gonzales Jr. – MessageToEagle.com – For the first time, astronomers at MIT and elsewhere have watched a black hole’s corona disappear, then reappear.
The cause of this dramatic transformation is unclear but a colliding star may have triggered the drastic transformation.
Like a pebble tossed into a gearbox, the star may have ricocheted through the black hole’s disk of swirling material, causing everything in the vicinity, including the corona’s high-energy particles, to suddenly plummet into the black hole.
The result, as the astronomers observed, was a precipitous and surprising drop in the black hole’s brightness, by a factor of 10,000, in under just one year.
“We expect that luminosity changes this big should vary on timescales of many thousands to millions of years,” says Erin Kara, assistant professor of physics at MIT, in a press release.
“But in this object, we saw it change by 10,000 over a year, and it even changed by a factor of 100 in eight hours, which is just totally unheard of and really mind-boggling.”
Astronomers continued to watch as the black hole began to slowly pull together material from its outer edges to reform its swirling accretion disk, which in turn began to spin up high-energy X-rays close to the black hole’s event horizon.
In just a few months, the black hole was able to generate a new corona, almost back to its original luminosity.
“This seems to be the first time we’ve ever seen a corona first of all disappear, but then also rebuild itself, and we’re watching this in real-time,” Kara says. “This will be really important to understanding how a black hole’s corona is heated and powered in the first place.”
With frequent observations, the researchers were able to catch the black hole as it precipitously dropped in brightness, in virtually all the wavebands they measured, and especially in the high-energy X-ray band — an observation that signaled that the black hole’s corona had completely and suddenly vaporized.
The researchers calculated that if a star indeed was the cause of the black hole’s missing corona, and if a corona were to form in a supermassive black hole of similar size, it would do so within a radius of about 4 light minutes — a distance that roughly translates to about 75 million kilometers from the black hole’s center.
“With the caveat that this event happened from a stellar tidal disruption, this would be some of the strictest constraints we have on where the corona must exist,” Kara says.
The findings are published in Astrophysical Journal Letters.
Written by Eddie Gonzales Jr. – MessageToEagle.com Staff