Magnetism Of Colliding Neutron Stars Can Power Gamma-Ray Bursts

GAMMA RAY BURSTS

After four decades of intense research into these enigmatic gamma-ray flashes, scientists have a good idea about the objects that can provide the enormous amounts of energies required: giant stars, or colliding compact stars.

Dublin - Apr 09, 2003
Calculations on one of the world's fastest supercomputers have allowed UK astrophysicists to shed light on what triggers gamma-ray bursts, the most powerful explosions in the universe.

The problem now is how all that energy can escape in less than a second. On Tuesday 8 April at the UK/Ireland National Astronomy Meeting in Dublin, Stephan Rosswog from the University of Leicester will present an explanation for this enigma.

Dr Rosswog's computer simulations, performed on the United Kingdom Astrophysical Fluids Facility (UKAFF), have now shown that the rapidly-spinning remains of colliding neutron stars can generate enormously strong magnetic fields, much the same as any magnetic field on Earth but many billion times stronger.

These ultra-strong magnetic fields can carry energy away from the collapsed remains of the two stars where it can escape in the form of gamma rays. This process is similar to that powering pulsars but the enormous magnetic field and the extremely fast spin (thousands of times per second) allows the energy to escape in less than a second rather than over many million years as in the case of pulsars.

"It is probably the biggest mystery of modern astronomy," says Stephan Rosswog. "These beasts were discovered almost four decades ago, but it is only now that we are beginning to shed light on what is at the heart of these tremendous explosions".

"They come in two flavours," explains Cambridge Astronomer Enrico Ramirez-Ruiz. "Long bursts go on for several tens of seconds while a typical short burst is over in a fraction of a second".

"Recent observations seem to tell us that long bursts are the death throes at the end of the lifetime of very massive stars," adds Melvyn Davies, also based at Leicester University, "but these short bursts are still even more of a mystery."

GAMMA RAY BURSTS

Spinning Black Hole Clue In Gamma-Ray Burst Signatures

Dublin - Apr 01, 2003
Spinning black holes could be responsible for at least some of the immensely powerful gamma-ray bursts (GRBs) astronomers observe coming from distant galaxies. On Tuesday 8 April, Sheila McBreen of University College, Dublin, will tell the UK/Ireland National Astronomy Meeting in Dublin that her analysis of the way gamma-rays were emitted over the course of outbursts from a large sample of GRBs has revealed particular signatures, most likely to be those of a rotating black hole either being "spun up" or "spun down".

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