Centaurus X-3

It has been suggested that Krzeminski's Star be merged into this article or section. (Discuss)

Centaurus X-3 (4U 1118-60) is an X-ray pulsar with a period of 4.84 seconds. It was the first X-ray pulsar to be discovered, and the third X-ray source to be discovered in the constellation Centaurus.

History

Centaurus X-3 was first observed during experiments of cosmic X-ray sources made on May 18, 1967. These initial X-ray spectrum and location measurements were performed using a sounding rocket.^[1] In 1971, further observations were performed with the Uhuru satellite, in the form of twenty-seven 100-second duration sightings. These sightings were found to pulsate with an average period of 4.84 seconds, with a variation in the period of 0.02 seconds. Later, it became clear that the period variations followed a 2.09 day sinusoidal curve around the 4.84 second period. These variations in arrival time of the pulses were attributed to the Doppler effect caused by orbital motion of the source, and were therefore evidence for the binary nature of Centaurus X-3.^[2]

System

Centaurus X-3 is located in the galactic plane about 8 kiloparsecs away, towards the direction of the Carina Spiral Arm, and is a member of an occulting spectroscopic binary system. The visible component is Krzeminski's Star, a 20.5 solar mass slightly evolved supergiant with a radius of 11.8 solar radii; the X-ray component is a compact 1 solar mass degenerate object in the form of a rotating magnetized neutron star.

The X-ray emission is fueled by the accretion of matter from the distended atmosphere of the blue giant falling through the inner Lagrangian point, L1. The overflowing gas probably forms an accretion disc and ultimately spirals inwards and falls on to the neutron star, releasing tremendous gravitational potential energy. The magnetic field of the neutron star channels the inflowing gas onto localized hot spots on the neutron star surface where the X-ray emission occurs.

The neutron star is regularly eclipsed by its giant companion every 2.09 days; these regular X-ray eclipses last approximately 1/4 the orbital period. There are also sporadic X-ray off durations.

The spin period history of Centaurus X-3 shows an obvious spin-up trend that is very prominent in the long term decrease in its pulse period. This spin-up was first noted to occur in Centaurus X-3 and Hercules X-1 and is now noted in other X-ray pulsars. The most feasible way of explaining the origin of this effect is by a torque exerted on the neutron star by accreting material.

See also

• X-ray pulsar
• Krzeminski's Star
• List of X-ray pulsars

References

External links

• Spin frequency history of Cen X-3
• Cen+X-3

Coordinates: 11^h 21^m 15.78^s, −60° 37′ 22.7″