|
Topic Name: New insight into GRB physics by using world largest telescopes
Category: Aeronautical
Research persons: Liverpool John Moores University and colleagues in the UK, Italy, France and Slovenia
Location: Astrophysics Research Institute,
Liverpool John Moores University,,Twelve Quays House,Egerton Wharf,,Birkenhead,,CH41 1LD, United Kingdom
Details
Gamma Ray Bursts (GRBs) are the most luminous, transient objects in the
Universe and represent the most significant new astrophysical phenomenon since
the discovery of quasars and pulsars. The discovery of X-ray and optical
transient sources associated with GRBs and the subsequent detection of
absorption lines in an optical afterglow that led to the first direct GRB
redshift measurement, have revolutionised our understanding of the GRB
phenomenon. X-ray transients are now observed for all long-duration GRBs but
optical afterglows have so far been detected in only 50% of these. Whether these
missing optical afterglows are inherently dark, dust absorbed, at high redshift
or just observationally overlooked is an open question. Similarly, there have
been few detections or well-sampled light curves of optical afterglows of
elusive short-duration GRBs.
Astrophysics Research Institute Scientists & some othersScientist 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.”
About
researcher:
David Bersier
Astrophysics Research Institute
Liverpool John Moores University
Twelve Quays House
Egerton Wharf
Birkenhead
CH41 1LD
United Kingdom
office: 7a
phn: +44 151 231 2939
fax: +44 151 231 2921
email: dfb "at" astro.livjm.ac.uk
(replace "at" by @ if you want to send me an email)
Mike Bode: Professor of Astrophysics PPARC
Senior Research Fellow
Dave Carter: Professor of Observational
Astronomy
Shiho Kobayashi :
Andrea Melandri :Group Secretary
Dr Carole G. Mundell
Astrophysics Research Institute,
Liverpool John Moores University,
12 Quays House,
Egerton Wharf,
Birkenhead, CH41 1LD cgm at astro livjm ac uk
Tel: +44 151 231 2917
Fax: +44 151 231 2921/2926
Andy Newsam
Robert Smith Astrophysics
Research Institute
Liverpool John Moores University
Twelve Quays House
Egerton Wharf
Birkenhead
CH41 1LD
UK
Tel: +44 151 2312903
Fax: +44 151 2312921
email:
rjs@astro.livjm.ac.uk
Iain Steele :Reader in Astronomical Techniques
Telescope Development Manager
Stephen Fraser :
Chris Mottram : Telescope Software Engineer
Andreja Gomboc (now at University of Ljubljana)
Cristiano Guidorzi (now at INAF, Osservatorio Astronomico di Brera)
Alessandro Monfardini (now at ITC-IRST and INFN, Trento)
Funding:
Funding for the LT has come from a variety of sources including
Liverpool John Moores University, the UK
Particle Physics and Astronomy Research
Council, the EU European
Regional Development Fund, and the generous benefaction of Mr Aldham Robarts.
The telescope is run as a UK National Facility for research on behalf of PPARC.
|
