X-Ray pulsar
Although all pulsars are neutron stars,
not all pulsars shine in the same way.
X-ray pulsars in particular illustrate
several ways in which pulsar emission
can originate.
Contents
Types of X-Ray Pulsars
Magnetospheric Emission
Like gamma-ray pulsars, X-ray pulsars can be
produced when high-energy electrons
interact in the magnetic field regions
above the neutron star magnetic poles.
Pulsars seen this way, whether in the
radio, optical, X-ray, or gamma-ray,
are often referred to as "spin-powered
pulsars," because the ultimate source of
energy comes from the gradual slowing
down of the neutron star rotation.
Cooling Neutron Stars
When a neutron star is first formed in a supernova, its surface is extremely hot (more
than 1,000,000,000 degrees). Over time,
the surface cools. While the surface is
still hot enough, it can be seen with X-ray telescopes. If some parts of the
neutron star are hotter than others
(such as the magnetic poles), then
pulses of thermal X-rays from the
neutron star surface can be seen as the
hot spots pass through our line of sight.
Some pulsars, including Geminga, show
both thermal and magnetospheric pulses.
Accretion
If a neutron star is
in a binary system with a normal star,
the powerful gravitational field of the
neutron star can pull material from the
surface of the normal star. As this
material spirals around the neutron
star, it is funneled by the magnetic
field toward the neutron star magnetic
poles. In the process, the material
is heated until it becomes hot enough to
radiate X-rays. As the neutron star
spins, these hot regions pass through
our line of sight and X-ray telescopes see these as X-ray
pulsars. Because the gravitational pull
on the material is the basic source of
energy for this emission, these are
often called "accretion powered
pulsars."
See also
