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. 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. 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.”

CONTACT

Dr Stephan Rosswog
Department of Physics and Astronomy, University of Leicester
University Road, LE1 7RH, Leicester, UK
Tel. (+44 (0)116 223 1219
Fax (+44 (0) 116 252 2070
E-mail: sro@star.le.ac.uk