Pulsars and neutron stars/Neutron star properties

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Introduction[edit]

Neutron star masses[edit]

A catalogue of pulsar and companion masses is available. Below we list the pulsar masses for systems in which the mass is well determined:

Pulsar Mass (solar masses)
J0337+1715 1.4378(13)
J0348+0432 2.01(4)
J0437-4715 1.44(7)
J0453+1559 1.559(5)
J0621+1001 1.53 +0.10-0.20
J0737-3039A 1.3381(7)
J0737-3039B 1.2489(7)
J0751+1807 1.26(14)
J1012+5307 1.64(22)
J1141-6545 1.27(1)
B1534+12 1.3330(4)
J1614-2230 1.97(4)
J1713+0747 1.31(11)
J1738+0333 1.47+0.07-0.06
J1756-2251 1.341(7)
J1802-2124 1.24(11)
J1807-2500B 1.3655(21)
B1855+09 1.58+10-13
J1903+0327 1.667(21)
J1906+0746 1.291(11)
J1909-3744 1.47(3)
J1910-5958A 1.3(2)
B1913+16 1.4398(2)
B2127+11C 1.358(10)
J2222-0137 1.20(14)
B2303+46 1.24-1.44

Neutron star radii[edit]

It is very difficult to make a direct determination of a neutron star radius. One method is to study X-ray bursters - these are neutron stars that are still accreting material from a companion in a close orbit. It is thought that they can build up layers of material on their surface until it reaches a critical mass at which point it undergoes a thermonuclear explosion causing a burst of emission from the surface. From a knowledge of the distance to the neutron star it is possible to estimate the radius of the neutron star. Results are obtained of around 9.6 to 11km (see e.g., Fujimoto & Gottwald 1989). More recently model spectra of neutron star atmospheres is used to fit the thermal X-ray spectra of neutron stars. Suleimanov et al. (2015) obtain radii of around 12km.

The neutron star interior[edit]

Neutron star cross section

Types of neutron stars[edit]

There is a large zoology of different types of neutron star. They can be differentiated between radio loud and radio quiet sources. Some are rotationally-powered whilst others are accretion-powered. There are now sources that switch between the different types. For instance, Papitto et al. discuss a neutron star (IGR J18245-2452; PSR J1824-2452I located in the globular cluster M28) which accretes matter and angular momentum from its companion star (this system is a low-mass X-ray binary; LMXB). During this stage, bright X-ray emission is observed. However, the rate of mass transfer can decrease and a radio millisecond pulsar switches on - in this state the emission is powered by the neutron star's rotating magnetic field.

Types of neutron star include:

  • radio pulsars
    • recycled pulsars
      • millisecond pulsars
    • magnetar
      • soft gamma ray repeater
      • anomalous X-ray pulsar
  • Low-mass X-ray binaries (LMXB)
  • Intermediate-mass X-ray binaries (IMXB)
  • High-mass X-ray binaries (HMXB)
  • Accretion powered pulsar

Quark stars[edit]