Centaurus X-3
Encyclopedia
Centaurus X-3 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
.
sources made on May 18, 1967. These initial X-ray spectrum and location measurements were performed using a sounding rocket
. 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.
, 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.
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...
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
Centaurus
Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.-Stars:...
.
History
Centaurus X-3 was first observed during experiments of cosmic X-rayX-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
sources made on May 18, 1967. These initial X-ray spectrum and location measurements were performed using a sounding rocket
Sounding rocket
A sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The origin of the term comes from nautical vocabulary, where to sound is to throw a weighted line from a ship into...
. In 1971, further observations were performed with the Uhuru
Uhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
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
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
caused by orbital motion of the source, and were therefore evidence for the binary nature of Centaurus X-3.
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 StarKrzeminski's Star
Krzeminski's Star is a 20.5 solar mass slightly evolved blue supergiant with a radius of 11.8 solar radii and spectral type O6.5II. It is estimate to be 8 kpc distant...
, a 20.5 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
slightly evolved
Stellar evolution
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years to trillions of years .Stellar evolution is not studied by observing the life of a single...
supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
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
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...
.
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
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...
, L1. The overflowing gas probably forms an accretion disc
Accretion disc
An accretion disc is a structure formed by diffuse material in orbital motion around a central body. The central body is typically a star. Gravity causes material in the disc to spiral inward towards the central body. Gravitational forces compress the material causing the emission of...
and ultimately spirals inwards and falls on to the neutron star, releasing tremendous gravitational potential energy
Potential energy
In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
. 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
Neutron star spin-up
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 pulsars...
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
Hercules X-1
Hercules X-1 , also known as 4U1656+35, is a moderately strong X-ray binary source first studied by the Uhuru satellite.It is composed of a neutron star accreting matter from a normal star probably due to Roche lobe overflow....
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.