Neutron star spin-up
Encyclopedia
Neutron star spin up is the name given to the increase in rotational speed over time first noted in Cen X-3 and Her X-1 but now observed in other X-ray pulsar
s. In the case of Cen X-3, the pulse period is decreasing at the rate of (defined as
) is 3.4*10^3 years.
The change in rotational period of the neutron star
comes from the transition region between the magnetosphere and the plasma
flow from the companion star. In this context the magnetosphere is defined as the region of space surrounding the neutron star, in which the magnetic field
determines the motion of the plasma. Inside the magnetic field, the plasma will eventually co-rotate with the neutron star while in the transition region, angular momentum
from the accretion disk will be transferred via the magnetic field to the neutron star, leading to the spin-up.
X-ray pulsar
X-ray pulsars or accretion-powered pulsars are a class of astronomical objects that are X-ray sources displaying strict periodic variations in X-ray intensity...
s. In the case of Cen X-3, the pulse period is decreasing at the rate of (defined as
) is 3.4*10^3 years.The change in rotational period of the neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
comes from the transition region between the magnetosphere and the plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
flow from the companion star. In this context the magnetosphere is defined as the region of space surrounding the neutron star, in which the magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
determines the motion of the plasma. Inside the magnetic field, the plasma will eventually co-rotate with the neutron star while in the transition region, angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...
from the accretion disk will be transferred via the magnetic field to the neutron star, leading to the spin-up.