Mathematicians Link Bright Flashes in Universe to "Parasitic" Black Holes

September 29, 2009

There's a new explanation for cosmic gamma-ray bursts, or intense electromagnetic beams produced by a collapsing star. The conventional model suggests that the source is plasma heated by neutrinos in a disk of matter forming around a black hole created when a star dies. But mathematicians at the University of Leeds hypothesize that the jets are a result of a black hole diving into a nearby star—and consuming it.

According to the research, when a star is invaded by a black hole in a binary system, the black hole acts like a parasite, spinning the star with gravitational forces on its way to the star's center. The star spins rapidly, which increases the duration of its demise. The central jet engine can last, according to sightings by the Swift satellite, about 3 minutes (or up to 10,000 seconds), which is longer than the neutrino model can explain. That would mean, instead, an electromagnetic origin of the jets.

"The neutrino model cannot explain very long gamma ray bursts and the Swift observations, as the rate at which the black hole swallows the star becomes rather low quite quickly, rendering the neutrino mechanism inefficient, but the magnetic mechanism can," said Serguei Komissarov. "Our knowledge of the amount of the matter that collects around the black hole and the rotation speed of the star allow us to calculate how long these long flashes will be—and the results correlate very well with observations from satellites."

The research, titled "Close Binary Progenitors of Long Gamma Ray Bursts," appeared in the Monthly Notices of the Royal Astronomical Society.

Source: University of Leeds, Sept. 18, 2009.