Lab Scientists Present Cosmic Findings To Astronomical Society

Jan. 7, 2002

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Lab Scientists Present Cosmic Findings To Astronomical Society

LIVERMORE, Calif — Two researchers at Lawrence Livermore National Laboratory will present preliminary findings today that show the association of unique gas flows to rapidly rotating black holes. This research is of special interest to organizations like the National Aeronautics and Space Administration (NASA) because it may help explain unusual periodic timing properties seen in the X-rays being emitted near many suspected black holes.

P. Chris Fragile and James Wilson, both in the Defense and Nuclear Technology Division at LLNL, and Professor Grant Mathews of the University of Notre Dame, will present their findings at the American Astronomical Society annual meeting in Washington DC from Jan. 7-10. Their work has centered around a computer simulation of the way these unique gas flows act in the vicinity of black holes. "Much of what the NASA Observers look for are X-rays, and the black holes produce a lot of that," Fragile said. "We’re hoping to simulate a system similar to what a NASA Observer might see when it looks at a black hole."

The work is based in part on Einstein's Theory of General Relativity — that is, rotating black holes will "drag" space-time around them, much as a tornado funnel cloud would. Any material falling toward the black hole will be caught up in this space-time whirlwind as it spirals ever closer to the black hole. Fragile, Wilson and Mathews also relied on previous research that found that gas falling into a black hole from a companion star possesses angular momentum, making it orbit the black hole in a disk-like pattern.
Recent advances in X-ray astronomy, such as the Rossi X-ray Timing Explorer (RXTE) and Chandra X-ray Observatory missions, make this a particularly fruitful time for theoretical work in this field.

"Our present work is an attempt to gain a better understanding of the motion of gas in the vicinity of rotating black holes through the use of extensive computer simulations," Fragile said of the research. "Simulations such as ours are critical since these environments are too complicated to study by any other means."

In their previous work, Fragile, Mathews and Wilson have suggested the so-called quasi-periodic brightness oscillations (QPOs) seen in the X-ray emission of many black-hole candidates may be related to this disk-like orbiting. In particular, one black hole in the Galactic X-ray source GRO J1655-40 (also called X-ray Nova Scorpii 1994) appears to be spinning very rapidly and seems to have an outer disk that is tilted relative to the angular momentum of the black hole. The current simulations being done are a first attempt to model the complicated disk dynamics around this object.

"Eventually, we’d like to simulate something the observers can go out and test, but we’re not there yet," Fragile said. "We think that this simulation is the first step toward that."

This research was supported in part by the National Science Foundation and the United States Department of Energy.

An image from the research can be found at

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