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Neutron Stars/X-ray Binaries
Accretion-powered pulsars are produced by matter flowing onto the neutron star,
whereas rotation-powered pulsars produce an outflow of matter. (In some cases, a
significant contribution to the X-ray emission can be from polar caps heated by
"instreaming" particles.) For the latter, rapid rotation is required. For the
former, an abundant source of infalling gas, such as a companion star is needed.
(See Binary and Multiple Star
Systems)
Some of the strongest X-ray sources in our galaxy are accreting neutron stars in
binary star
systems. With Chandra, astronomers have detected hundreds of such objects in
other galaxies as well. Accreting neutron stars exhibit various behaviors thought
to be related to the details of how the matter falls onto the neutron star. Some
pulse steadily, some flicker in a quasi-periodic way, some burst explosively,
some eject jets of high-energy particles. If you have a java-enabled browser, you
can view our animation and discussion of X-ray pulsars.
A black hole in a
binary system could also produce an accretion-powered source. Since black holes
do not have a surface or a magnetic pole in the normal sense of the word, they
cannot produce regular X-ray pulses, though they may flicker.
More: SCO X-1
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