The source of the X-ray emissions is thought to be ultrahot material in the innermost regions of the accretion disk, which is just about to fall into the black hole. Scientists have observed these bursts in the optical, ultraviolet, and X-ray bands, and also occasionally in the radio end of the spectrum. This entire process generates colossal bursts of energy across the electromagnetic spectrum. In the aftermath, a shower of stellar debris rains down and gets caught up in an accretion disk - a swirl of cosmic material that eventually funnels into and feeds the black hole. However, a black hole's gravitational forces are so immense that they can disrupt the star, stretching and flattening it like a pancake and eventually shredding the star to pieces. Pasham and his collaborator, Sjoert van Velzen of Johns Hopkins University, report their results in a paper published this week in the Astrophysical Journal.īased on theoretical models of black hole evolution, combined with observations of distant galaxies, scientists have a general understanding for what transpires during a tidal disruption event: As a star passes close to a black hole, the black hole's gravitational pull generates tidal forces on the star, similar to the way in which the moon stirs up tides on Earth. "That's the perfect opportunity to study such things from scratch, essentially." "You can do this only with these special events where the black hole is just sitting there doing nothing, and then suddenly along comes a star, giving it a lot of fuel to power itself," Pasham says. Pasham says scientists have suspected that black hole jets are powered by their accretion rate, but they have never been able to observe this relationship from a single event. This is the first time we've seen a jet that's controlled by a feeding supermassive black hole." "A well-fed black hole produces a strong jet, while a malnourished black hole produces a weak jet or no jet at all. "This is telling us the black hole feeding rate is controlling the strength of the jet it produces," Pasham says. Instead, they appear to be evidence of a giant jet of highly energetic particles streaming out from the black hole as stellar material is falling in.ĭheeraj Pasham, a postdoc in MIT's Kavli Institute for Astrophysics and Space Research, says the highly similar patterns suggest that the power of the jet shooting out from the black hole is somehow controlled by the rate at which the black hole is feeding on the obliterated star. They believe these radio "echoes," which are more than 90 percent similar to the event's X-ray emissions, are more than a passing coincidence. Scientists from MIT and Johns Hopkins University have now detected radio signals from the event that match very closely with X-ray emissions produced from the same flare 13 days earlier.
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