Astronomers Look Forward To ’Swift’ Studies Of Cataclysmic Explosions

Gamma ray bursts (GRBs) are the most powerful explosions in the Universe, yet it is only in the last few years that astronomers have started to understand them. This ongoing quest to solve the mysteries of gamma ray bursts will be boosted next September when a new US/UK/Italian space observatory, called Swift, will be launched.

Dr. Julian Osborne (University of Leicester) will describe this exciting mission and the discoveries that can be expected from Swift on Tuesday 30 March, during the RAS National Astronomy Meeting in Milton Keynes.

At present only one GRB is announced each month on average. Studies of these dramatic events are also complicated by their short duration and random location in the sky – GRBs typically last between less than 1 to around 100 seconds.

Although GRBs detected by orbiting spacecraft are now announced instantaneously, the delay in making observations with X-ray space observatories and optical telescopes often lasts many hours, by which time the ’afterglow’ of the explosion has faded to a shadow of its former self – many thousands of times fainter than it was initially. This makes it much more difficult to understand the processes that power these brief but cataclysmic explosions.

Dedicated to understanding these remarkable, transient events, Swift is quite unique in its ability to automatically respond as soon as a gamma ray burst appears. After launch in September, the large area Burst Alert Telescope (BAT) on Swift will detect around 10 GRBs a month.

When the BAT detects a GRB it will send a request to the onboard spacecraft control system to turn towards the burst. Within one minute the rapidly slewing spacecraft will be on-target, allowing its Ultraviolet-Optical Telescope and X-Ray Telescope to start collecting observations. For the first time, astronomers will be able to gather numerous observations of GRBs during their most energetic phase, with the promise of new insights into their nature.

The Ultraviolet-Optical and X-Ray Telescopes on Swift have major UK involvement. The Mullard Space Science Laboratory (MSSL) of University College London has provided the Ultraviolet-Optical telescope, a 30 cm image-intensified instrument with rapid readout. The X-Ray Telescope’s camera and other subsystems were provided by the University of Leicester.

These instruments make use of the designs and spare parts from the successful XMM-Newton observatory, ESA’s cornerstone X-ray facility for which these groups provided similar instruments. Both MSSL and the University of Leicester will continue to look after their instruments when Swift is in orbit, and a UK Swift data centre will be set up at Leicester. They will also be providing rapid alerts, checking the Swift results and alerting telescopes around the world so that astronomers will be able to respond as soon as a GRB is detected.

“It will be a very busy and exciting time when Swift starts finding GRBs,” said Dr. Osborne. “Swift will tell astronomers about the massive explosions and the death of stars, both important events in their own right.

“But because the GRBS are so very bright, Swift offers the tantalizing prospect of seeing the very first generation of stars and may even set the record for the most distant objects ever seen. Bright and distant GRBs will also allow astronomers to ‘X-ray’ all the matter between us and the GRB, providing important clues to the evolution of the universe.”