Jodrell Bank astronomers find new type of star (Forwarded)

Jodrell Bank Observatory
University of Manchester
Macclesfield, U.K.

Further Information:

Professor Andrew Lyne, University of Manchester
+44 1477 571321

Dr Maura McLaughlin, University of Manchester
+44 1477 537751

Dr Michael Kramer, University of Manchester
+44 1477 571321

Dr Dick Manchester, CSIRO Australia Telescope National Facility
+61-2-9372-4313

Professor Nichi D'Amico, Cagliari Astronomical Observatory
+39-070-711-80-208

Dr Fernando Camilo, Columbia Astrophysics Laboratory, Columbia University
+1-212-854-2540

Dr Ingrid Stairs, University of British Columbia
+1-604-822-6796

Dr James Cordes, Cornell University
+1-607-255-0608

Ian Morison, University of Manchester (for media assistance)
+44 1477 571321

Embargoed until 18:00 GMT 15 February 2006

Jodrell Bank astronomers find new type of star

Astronomers of the University of Manchester's Jodrell Bank Observatory
(UK) have led an international team which used the Parkes radio telescope
in Australia to find a new kind of cosmic object which sends out radio
flashes. These flashes are very short and very ra one hundredth of a
second long, the total time the objects are visible amounts to only about
one tenth of a second per day.

The discovery will be published in this week's issue of the journal
Nature.

Eleven sources of flashes have been found in different parts of the plane
of the Milky Way in a survey for radio pulsars, which are small,
compressed, highly-magnetised, neutron stars that produce regular pulses
as they rotate, like cosmic light-houses. While that survey found over 800
pulsars and is the most successful in history, it also uncovered this new
type of star. Rather than searching only for the periodic trains of
pulses, the astronomers developed new techniques for detecting single
short bursts of radiation.

Dr Maura McLaughlin explained: "It was difficult to believe that the
flashes we saw came from outer space, because they looked very much like
man-made interference". The isolated flashes last for between 2 and 30
milliseconds. In between, for times ranging from 4 minutes to 3 hours, the
new stars are silent.

After confirmation of their celestial nature, studies over the next 3
years revealed that 10 of the 11 sources have underlying periods of
between 0.4 seconds and seven seconds.

"The periodicities found suggest that these new sources are also rotating
neutron stars, but different from radio pulsars", says Professor Andrew
Lyne. "It is for this reason that we call them Rotating Radio Transients
or RRATs. It's as if, following a flash, a RRAT has to gather its strength
during perhaps a thousand rotations before it can do it again!"

RRATs are a new flavour of neutron stars in addition to the conventional
radio pulsars and to the magnetars, which are also believed to be rotating
neutron stars and are known to give off powerful X-ray and gamma-ray
bursts. It is possible that RRATs represent a different evolutionary phase
of neutron stars to or from magnetars.

The new objects probably far outnumber both their cousins. "Because of
their ephemeral nature, RRATs are extremely difficult to find and so we
believe that there are about 4 RRATs for every pulsar," says Dr Richard
Manchester of the Australia Telescope National Facility. He is part of the
team which also includes astronomers from the US, Canada and Italy.

Publication

M.A. McLaughlin, A.G Lyne, D.R Lorimer, M. Kramer, A.J Faulkner, R.N
Manchester, J.M. Cordes, F. Camilo, A. Possenti, I.H. Stairs, G. Hobbs, N.
D'Amico, M. Burgay and J.T, O'Brien. "Transient radio bursts from rotating
neutron stars" 2006. Nature, 439, pp 817-820. Online at
http://xxx.lanl.gov/abs/astro-ph/0511587

Background Information

A pulsar is a neutron star, which is the collapsed core of a massive star
that has ended its life in a supernova explosion. Weighing more than our
Sun, yet only 20 kilometres across, these incredibly dense objects produce
a beam of radio waves which sweeps around the sky like a lighthouse, often
hundreds of times a second. Radio telescopes receive a regular train of
pulses as the beam repeatedly crosses the Earth so the object is observed
as a pulsating radio signal.

The Parkes survey which discovered 800 pulsars and the RRATs reported
here, uses a multi-beam system installed on the 64-metre Parkes Radio
Telescope in New South Wales, Australia. The powerful "multibeam" receiver
was built as a joint venture between engineers at the Australia Telescope
National Facility and the University of Manchester's Jodrell Bank
Observatory.

The receiver gives the telescope 13 beams capable of scanning the sky
simultaneously and, as Professor Andrew Lyne of the University of
Manchester explained, "It's like having over a dozen giant radio
telescopes operating at once". As a result, the system requires 13 sets of
sophisticated data acquisition systems, one for each beam, which were
largely developed and built by the UK and Italian groups.

The Jodrell Bank work was supported by funding from the UK Particle
Physics and Astronomy Research Council (PPARC).

Further information on pulsars can be found on the Jodrell Bank
Observatory Pulsar Group pages,
http://www.jb.man.ac.uk/research/pulsar/

Figures

[Image 1:
http://www.jb.man.ac.uk/news/rrats/virtual.jpg (550KB)]
Visualisation of a neutron star, showing the magnetic field lines (cut
away) and the radio beam (Credit: Russell Kightly Media).

[Image 2:
http://www.jb.man.ac.uk/news/rrats/RRATS.jpg (1.46MB)]
Visualisation of a neutron star, showing the magnetic field lines and the
radio beam emanating from a magnetic pole (Credit: Michael Kramer/Ian
Morison).

[Image 3:
http://www.jb.man.ac.uk/news/rrats/RRATSpulse.jpg (2.27MB)]
A flash from a RRAT, showing the sweep in radio frequency which is the
signature of a particular RRAT.

[Image 4:
http://www.jb.man.ac.uk/news/rrats/pksmultibeam.jpg (238KB)]
The multibeam receiver used in the discovery being installed on the 64
meter radiotelescope at Parkes, New South Wales, Australia.

[Image 5:
http://www.jb.man.ac.uk/news/rrats/Parkes.jpg (4.58MB)]
The 64 meter Parkes radiotelescope, New South Wales, Australia. (Credit:
Shaun Amy).