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Gamma-ray burst identification earns top prize

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Gamma-ray burst identification earns top prize


January 12, 1998: Dr. Jan van Paradijs of the University of Alabama in Huntsville and The University of Amsterdam last week shared in the Bruno Rossi prize awarded annually by the American Astronomical Society "for a significant contribution to High Energy Astrophysics, with particular emphasis on recent, original work."

Van Paradijs led a team that identified the first known optical counterpart for a gamma-ray burster in February 1997. He shares the award with the team that operates the Dutch-Italian BeppoSAX X-ray astronomy satellite which discovered the burst.

NASA/Marshall's Dr. Gerald Fishman, principal investigator for the Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma-Ray Observatory, won in 1994 "for his signal contributions" to that project and to solving "the continuing puzzle of the Gamma-ray Bursts."

Van Paradijs is the Pei-Ling Chan eminent scholar in astrophysics at UAH works on several BATSE research projects. One of the world's leading astrophysicists, van Paradijs was appointed to fill UAH's eminent scholar chair in astrophysics in 1993. He is a professor of astronomy, and splits his time between Amsterdam and Huntsville, where he collaborates with the BATSE team.

"We are extremely pleased that a person associated with the BATSE research team has won this prestigious prize," Fishman said.

Since the 1970s astrophysicists have been baffled by bursts of gamma radiation which appear at random times and locations in the sky. The BATSE instrument on the Compton Observatory was expected to show that the bursts come from within our own Milky Way galaxy. Instead, BATSE observations showed that the bursts most likely originate near the "edge" of the observable universe.

This only deepened the mystery of where gamma-ray bursts occur. Until early 1997, no counterpart had been seen in X-rays, visible light, or radio waves.

That changed when BeppSAX observed a burst - GRB970228 - on Feb. 28, 1997. The BeppoSAX team was able to narrow the possible location, and van Paradijs, using optical and radio telescopes on Earth, found a brilliant object in the location box just 21 hours later. The object was not in previous images of the area. A week later, the object had faded, and the Hubble Space Telescope soon confirmed that the source was fading. It also faded below BeppoSAX's sensitivity, from 1/5,000th the brightness of the Crab Nebula to nothing in just three days.

Hubble Images of GRB 970228

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The Wide-field Planetary Camera Image from Hubble of the burst region in the Visual band. The optical source believed to be the home of the gamma-ray burst is at the center of the photograph.

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A Close-Up of the Optical Transient taken not long after the burst shows both a point-like source (the bright emission) plus the extended emission (below and to the right) from what may be the distant host-galaxy.

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A later Hubble image taken in September reveals that the optical counterpart to the gamma-ray burst is still visible, indicating to astronomers that these objects are indeed from the most distant parts of the Universe.

"To me, this is fairly convincing evidence that the transient X-ray and optical sources are the same, and that both are associated with the gamma-ray burst," van Paradijs said at UAH. "If these transients are from the distant galaxy, we have, for the first time, found the site of a gamma-ray burst."

The discovery also supports theories that gamma-ray bursts happen at great distances - and thus, very early in the history of the universe. The mystery continues, though. While we have a better idea of where to look, the counterparts that have been observed still are too faint to let astronomers pin down the source (or sources).

Gamma-ray burst also took center stage earlier at the AAS conference. This story links to earlier NASA/Marshall coverage of gamma-ray bursts and a recent symposium on the subject.


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Author: Dave Dooling
Curator: Bryan Walls
NASA Official: John M. Horack