New-Found Pulsars Start to Crack Gamma-Ray Source Mystery
Jodrell Bank Observatory
University of Manchester, UK.
10 April 2001 – For immediate release
Astronomers from the University of Manchester and other members of an
international team using the Parkes 64-m radio telescope in Australia have
found about 30 young, energetic pulsars, which may be the counterparts of
otherwise unidentified Galactic gamma-ray sources. The positions of these
sources can be uncertain by as much as a degree so making it difficult to
identify their origin. Two of the newly discovered pulsars have positions
which coincide within the positional uncertainties to hitherto unidentified
gamma-ray sources detected by the EGRET (Energetic Gamma Ray Experiment)
instrument on the Compton Gamma Ray Observatory satellite.
Young pulsars have long been favoured as potential counterparts – the two
most powerful gamma-ray sources in the sky are the Crab and Vela pulsars –
and both of these new pulsars linked to gamma-ray positions are young and
energetic. PSR J1420-6048, with a period of 68 ms, appears to be 13,000
years old. PSR J1837-0604, with a period of 96 ms, is estimated to be 34,000
years old. The increasing rotation periods observed for both pulsars
indicates that they are losing energy at a significant rate. “For this
reason alone one would expect that they should be observable as gamma-ray
sources,” said Dr. Nichi D’Amico of the Osservatorio Astronomico di Bologna,
Italy, as he presented the results at the “Gamma-Ray Astrophysics 2001”
Symposium in Baltimore.
Gamma-ray observations were pioneered in the 1970s by the SAS-2 and COS-B
satellites, launched by NASA and ESA respectively. But three decades later
many gamma-ray sources still defy identification. To date, less than half of
the gamma-ray sources observed with EGRET have been identified. Seven
gamma-ray sources near the Galactic plane have previously been identified as
pulsars. “We’ve now found a further two pulsars that coincide with
unidentified EGRET sources, within the positional uncertainties,” added Dr.
D’Amico.
Pulsars are neutron stars formed in the collapse of massive stars in
supernova explosions. As Professor Andrew Lyne of the University of
Manchester explains: “their intense magnetic fields are expected to make
them profilic sources of high-energy radiation.”
The pulsars were found in the Parkes multibeam survey using a 13-beam,
1400-MHz receiver on the Parkes radio telescope to search for young, distant
pulsars within five degrees of the Galactic Plane. Although not yet
complete, this survey is already the most successful survey for radio
pulsars ever made, having found more than 600 previously unknown pulsars,
nearly doubling the number previously found in 30 years of observations.
The Parkes survey has found 30 radio pulsars with ages less than 100,000
years. The survey team will now do precise, long-term timing of their
periods in order to help future gamma-ray observatories detect any gamma-ray
pulses from these objects.
“The Parkes multibeam pulsar survey has been very good at finding faint,
fast pulsars,” said Professor Victoria Kaspi of McGill University. “It
turned up these two energetic young objects even without deliberately
targeting the gamma-ray-source error boxes.” With this encouragement the
team plans to use the multibeam system to target more of these sources with
even higher sensitivity and will expect to find many more gamma-ray emitting
pulsars. If so, the nature of these mysterious galactic gamma-ray sources
may soon be solved.
The members of the research team are Dr. D’Amico, Professor Victoria Kaspi
(McGill University, Canada), Dr. Richard Manchester (Australia Telescope
National Facility, Australia), Dr. Fernando Camilo (Columbia University,
USA), Professor Andrew Lyne (University of Manchester, Jodrell Bank
Observatory), Dr. Andrea Possenti (Osservatorio Astronomico di Bologna,
Italy), Dr. Ingrid Stairs (National Radio Astronomy Observatory, USA), Dr.
Michael Kramer and Mr George Hobbs (University of Manchester, Jodrell Bank
Observatory), and Dr. Jon Bell (Australia Telescope National Facility,
Australia).
The text of this release and two supporting images can be found at:
http://www.jb.man.ac.uk/news/newpulsars/
CONTACTS:
Prof. Andrew Lyne, University of Manchester, Jodrell Bank Observatory
phone +44-1477-572-640 e-mail agl@jb.man.ac.uk
Dr. Nichi D’Amico, Osservatorio Astronomico di Bologna, Italy
phone +39-051-209-5719 e-mail DAMICO@astbo3.bo.astro.it
Prof. Victoria Kaspi, McGill University, Canada
phone +1-514-398-6412 e-mail vkaspi@physics.mcgill.ca
Dr. Richard Manchester, Australia Telescope National Facility
phone +61-2-9372-4313 e-mail rmanches@atnf.csiro.au
Dr. Ingrid Stairs, National Radio Astronomy Observatory, U.S.A.
phone +1-304-456-2213 e-mail istairs@nrao.edu
Background Information:
The Parkes radio telescope is part of the Australia Telescope, which is
funded by the Commonwealth of Australia for operation as a National
Facility managed by CSIRO (Commonwealth Scientific and Industrial Research
Organisation). Nichi D’Amico and Andrea Possenti received support from the
Italian Space Agency and from the Italian Minister of the University and
Technological and Scientific Research (MURST). Victoria Kaspi is an Alfred
P. Sloan Research Fellow and received support from an NSF CAREER award
(AST-9875897) and an NSERC grant (RGPIN228738-00). Fernando Camilo is
supported by NASA grant NAG 5-3229. Ingrid Stairs received support from
NSERC and Jansky postdoctoral fellowships.
