Scientists have used the world's largest robotic telescope to make the earliest-ever measurement of the optical polarisation* of a Gamma Ray Burst (GRB) just 203 seconds after the start of the cosmic explosion. This finding, which provides new insight into GRB physics, is published in Science today (15th March 2007).
The scientists from Liverpool John Moores University and colleagues in the UK, Italy, France and Slovenia used the Liverpool Telescope on the island of La Palma and its novel new polarimeter, RINGO, to perform the measurement following detection of the burst by NASA's Swift satellite.
Gamma Ray Bursts are the most instantaneously powerful explosions in the Universe and are identified as brief, intense and completely unpredictable flashes of high energy gamma rays on the sky. They are thought to be produced by the death throes of a massive star and signal the birth of a new black hole or neutron star (magnetar) and ejection of an ultra-high speed jet of plasma. Until now, the composition of the ejected material has remained a mystery and, in particular the importance of magnetic fields has been hotly debated by GRB scientists.
The Liverpool measurement was obtained nearly 100 times faster than any previously published optical polarisation measurement for a GRB afterglow and answers some fundamental questions about the presence of magnetic fields.
Principal author of the Science paper and GRB team leader Dr Carole Mundell of the Astrophysics Research Institute, Liverpool John Moores University, said "Our new measurements, made shortly after the Gamma Ray Burst, show that the level of polarisation in the afterglow is very low. Combined with our knowledge of how the light from this explosion faded, this rules-out the presence of strong magnetic fields in the emitting material flowing out from the explosion - a key element of some theories of GRBs."
The so-called optical afterglow is thought to originate from light emitted when this ejected material impacts the gas surrounding the star. In the first few minutes after the initial burst of gamma rays, the optical light carries important clues to the origin of these catastrophic explosions; capturing this light at the earliest possible opportunity and measuring its properties is ideally suited to the capabilities of large robotic telescopes like the Liverpool Telescope.
Lord Martin Rees, Astronomer Royal and President of the Royal Society said "We are still flummoxed about the underlying 'trigger' for gamma ray bursts, and why they sometimes emit bright flashes of light. Theorists have a lot of tentative ideas, and these observations narrow down the range of options."
Professor Keith Mason, CEO of the Particle Physics and Astronomy Council (PPARC) and UK lead investigator on Swift’s Ultra Violet/Optical Telescope, said, "This result demonstrates well the effectiveness of Swift’s rapid response alert system, allowing robotic telescopes, such as the Liverpool Telescope, to follow up gamma ray bursts within seconds, furthering our knowledge with each detection."
Contacts
Gill Ormrod – PPARC Press Office
Tel: +44 1793 442012.
Email: gill.ormrod@pparc.ac.uk
Shonagh Wilkie – Liverpool John Moores University Press Office
Tel: +44 151 231 3346. Mobile: 07968 422508
Email: s.wilkie@ljmu.ac.uk
Science Contact
Dr Carole Mundell – Liverpool John Moores University
Tel. +44 151 231 2917. Mobile: 07974 779923.
Email: cgm@astro.livjm.ac.uk
Images
The following images will be available from the following link
http://www.pparc.ac.uk/Nw/LT_grb.asp after the embargo has expired (6pm GMT).
Figure showing the links between the gamma ray burst detection and follow up observations.
Credit: Dr Carole Mundell, Liverpool John Moores University.
Figure caption:
(1) Gamma Ray Burst, GRB 060418, explodes and emits high-energy gamma rays
(2) and (3) Swift satellite detects gamma rays and sends notification of sky location to ground telescopes
(4) Liverpool Telescope (LT) on mountain top on Canary island of La Palma receives notification and immediately points to correct part of sky to begin to capture optical light from GRB afterglow.
(5) Polarisation image taken with LT polarimeter, RINGO, is transmitted to the Astrophysics Institute at Liverpool John Moores University for analysis by scientists.
Image of Liverpool Telescope
Credit: Liverpool Telescope/JMU
An artist’s impression of NASA’s Swift spacecraft with a gamma ray burst in the background. Credit: Spectrum and NASA E/PO, Sonoma State University.
Notes for Editors
*Optical polarisation - optical light is part of the electromagnetic spectrum and, as such is a wave with an electric vector, or vibration direction, that is usually randomly orientated relative to the direction of travel of the wave - this is unpolarised light. When the light is produced by electrons that travel in a well-ordered magnetic field, the electric vector of the emitted light keeps a preferred direction - this alignment causes the light to be polarised. Measuring the amount of polarisation of light therefore probes the presence and structure of any guiding magnetic field in the object that has emitted the light.
The Liverpool Telescope is a 2m optical and infrared robotic telescope that stands 2400m above sea level on a mountain top on the Canary Island of La Palma. It took its first images of the GRB’s in 2004 and is specially designed to respond very rapidly to notification of cosmic explosions by X-ray and gamma-ray satellites such as NASA's Swift satellite. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University at the Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
RINGO is a Liverpool Telescope fast-track instrument internally funded by the Astrophysics Research Institute of Liverpool John Moores University.
Liverpool team's discovery was made possible by the entire process of detection, identification and intensive follow-up monitoring being carried out automatically with no human intervention. This was possible thanks to the fully robotic nature of the telescope and its instrumentation, and the sophisticated object identification software developed by the Liverpool team.
The telescope was designed, constructed and commissioned by Telescope Technologies Limited, a subsidiary company of Liverpool John Moores University. The telescope is supported by the Particle Physics and Astronomy Research Council, making 40% of the observing time available to astronomers throughout the UK.
Link to previous PPARC release - http://www.pparc.ac.uk/nw/press/robotic_telescope.asp
The paper’s lead author, Dr Carole Mundell from Liverpool John Moores University, is funded by the Royal Society’s University Research Fellowship Scheme and is a RCUK academic fellow.
Websites
Liverpool Telescope - http://telescope.livjm.ac.uk/
Swift - http://www.nasa.gov/mission_pages/swift/main/index.html
Swift, a medium-class explorer mission, is managed by NASA Goddard. Swift is a NASA mission with participation of the Italian Space Agency and the Particle Physics and Astronomy Research Council in the United Kingdom. It was built in collaboration with national laboratories, universities and international partners, including Penn State University; Los Alamos National Laboratory in New Mexico; Sonoma State University, Rohnert Park, Calif.; Mullard Space Science Laboratory in Dorking, Surrey, England; the University of Leicester, England; the Brera Observatory in Milan; and ASI Science Data Center.
The Particle Physics and Astronomy Research Council (PPARC) is the UK’s strategic science investment agency. It funds research, education and public engagement in four areas of science - particle physics, astronomy, cosmology and space science.
PPARC is government funded and provides research grants and studentships to scientists in British universities, gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Laboratory for Particle Physics (CERN), and the European Space Agency. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at Jodrell Bank observatory.
PPARC is a partner in the British National Space Centre [BNSC] which coordinates the UK’s civil space activities.