Fernando Camilo
Columbia Astrophysics
Laboratory
Columbia University, New York
City
Pulsars are
remarkable objects, which our group
studies using a variety of radio, X-ray, and optical telescopes. Some
examples of this work are shown below.
Young neutron stars
Approximately once per century a neutron star is born in our
Galaxy. Young ones are therefore rare, and located near the Galactic
plane where massive stars that undergo supernova explosions
reside.
Evidence of these neutron stars can be provided by X-ray and radio
study of their associated supernova
remnants or by detection of the strong pulsar winds confined by the
local environment.
Actual detection of the rotation period from the neutron stars
(usually at radio wavelengths) can be exceedingly maddening owing to
their faintness
(a high tolerance for boredom comes in handy when searching for them),
and only about a dozen such pulsars younger than 10000 years are
known.
Can you spot 5 such neutron stars in this montage of Chandra X-ray and VLA radio images?
Even rarer than these ordinary young neutron stars are the magnetars. These are
seen as bright X-ray sources, powered by the decay of stupendously
strong magnetic fields.
Magnetars don't emit radio waves — except when they
do. In that case, they can show rather surprising
behavior.
Globular clusters
The astonishingly dense central environments of some globular
clusters encourage the close interaction of stellar systems. One
outcome is a large incidence of tight binaries, and in particular a
variety of very old neutron stars.
This is the beautiful cluster 47 Tucanae, as
observed with the Chandra
X-ray observatory, in which we know of more than 20
millisecond pulsars.
Terzan 5 is another exceptional cluster, where more than 30
pulsars are now known, including one spinning 716
times every second. This is faster than most kitchen blenders —
with a mass larger than our Sun's, and an equatorial speed about 15%
that of light!
Surveys
In 1997-2002 we used the Parkes telescope to search
along the Galactic plane for distant radio pulsars with a sensitivity
nearly 10 times better than previous surveys. We did this at a
wavelength of 20 cm (1400 MHz) using the fabulous
13-beam receiver, and a data-acquisition system that we developed
at Jodrell Bank observatory and
ATNF. We discovered nearly 750
pulsars, doubling the known population, including very
unusual, young,
and binary
neutron stars.
In another such "undirected" survey we found an ultra-relativistic
binary that turned out to be the only-known and extraordinary double
pulsar.
We are now using a 7-beam receiver at the
Arecibo telescope to do an even deeper
census of the Galactic plane.
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