1.3 The Name, Classification and Distribution
19
there are 350 thousand radio pulsars whose radiation fluxes are more than 0.3 mJy, in
which if the radiating beams of 20% sweep across through the Earth, there would be
70 thousand pulsars to be found, while the total of pulsars in the Milky Way system
be more than 200 thousand. Certainly, if their radiating beams do not sweep across
nearby the Earth, the pulsars are unable to be discovered.
There are 759 X-ray sources catalogued in the Galactic coordinate system, where
population of the LMXB is 290, that of the HMXB is 152, that of Cataclysmic
Variable stars (CV) is 141, that of X-ray Neutron Stars (NS) is 95, that of Active
Galactic Nuclei (AGN) is 6 and that of other X-ray sources is 75 [19]. The Galactic
coordinate system is a celestial coordinate system in spherical coordinates, with the
Sun as its center, the primary direction aligned with the approximate center of the
Milky Way system, and the fundamental plane parallel to an approximation of the
Galactic plane but offset to its north. It uses the right-handed convention, meaning
that coordinates are positive toward the north and toward the east in the fundamental
plane. The Galactic longitude measures the angular distance of an object eastward
along the Galactic equator from the Galactic center. The Galactic latitude measures
the angle of an object north or south of the Galactic equator as viewed from the Earth,
and is positive to the north and negative to the south. Both the Galactic longitude
and latitude are measured in degrees. The X-ray sources exist throughout the X-ray
sky, as is evident from their space distributions, although the clustering near the
Galactic plane is clear. The 95 neutron stars include 68 RP pulsars, 11 AX pulsars,
3 Soft Gamma-ray Repeaters (SGR) and 13 other neutron stars, which are uniform
distribution relative to the Galactic plane. Most of the pulsars are located nearby in
the Galactic plane, and a few of the pulsars located in the region with high Galacticlatitude and relatively distant distance. In the international celestial reference system
at epoch J2000.0, distributions of the RP pulsars mostly concentrated on the region
with the declination from −60 to +60°.
The statistical results of the pulsars with remarkable features are listed in
Table 1.2, where SAX denotes an Italian-Dutch X-ray astronomy satellite launched
in 1996, named BeppoSAX. The names, distances and characteristic ages of the
pulsars with a distance of less than 300 parsecs are listed in Table 1.3. It can be
seen from Tables 1.2 and 1.3 that these catalogued pulsars are mostly located in the
Galactic System, their distance are from hundreds to tens of thousands of light years,
and their characteristic ages from tens of thousands to billions of years. Among
the discovered and catalogued pulsars, population of the pulsars with the emitting
signals in the optical or gamma-ray frequency bands is relatively few. There are
6 optical pulsars, including PSR B0531+21 (Crab Pulsar), PSR J0835–4510 (Vela
Pulsar), PSR B0540–69 (LMC), PSR B0656+14, PSR B0633+17 (Geminga) and
PSR B1509-58. There are around 100 gamma-ray pulsars, mostly discovered by the
Fermi Gamma-ray Space Telescope (FGST).
19
there are 350 thousand radio pulsars whose radiation fluxes are more than 0.3 mJy, in
which if the radiating beams of 20% sweep across through the Earth, there would be
70 thousand pulsars to be found, while the total of pulsars in the Milky Way system
be more than 200 thousand. Certainly, if their radiating beams do not sweep across
nearby the Earth, the pulsars are unable to be discovered.
There are 759 X-ray sources catalogued in the Galactic coordinate system, where
population of the LMXB is 290, that of the HMXB is 152, that of Cataclysmic
Variable stars (CV) is 141, that of X-ray Neutron Stars (NS) is 95, that of Active
Galactic Nuclei (AGN) is 6 and that of other X-ray sources is 75 [19]. The Galactic
coordinate system is a celestial coordinate system in spherical coordinates, with the
Sun as its center, the primary direction aligned with the approximate center of the
Milky Way system, and the fundamental plane parallel to an approximation of the
Galactic plane but offset to its north. It uses the right-handed convention, meaning
that coordinates are positive toward the north and toward the east in the fundamental
plane. The Galactic longitude measures the angular distance of an object eastward
along the Galactic equator from the Galactic center. The Galactic latitude measures
the angle of an object north or south of the Galactic equator as viewed from the Earth,
and is positive to the north and negative to the south. Both the Galactic longitude
and latitude are measured in degrees. The X-ray sources exist throughout the X-ray
sky, as is evident from their space distributions, although the clustering near the
Galactic plane is clear. The 95 neutron stars include 68 RP pulsars, 11 AX pulsars,
3 Soft Gamma-ray Repeaters (SGR) and 13 other neutron stars, which are uniform
distribution relative to the Galactic plane. Most of the pulsars are located nearby in
the Galactic plane, and a few of the pulsars located in the region with high Galacticlatitude and relatively distant distance. In the international celestial reference system
at epoch J2000.0, distributions of the RP pulsars mostly concentrated on the region
with the declination from −60 to +60°.
The statistical results of the pulsars with remarkable features are listed in
Table 1.2, where SAX denotes an Italian-Dutch X-ray astronomy satellite launched
in 1996, named BeppoSAX. The names, distances and characteristic ages of the
pulsars with a distance of less than 300 parsecs are listed in Table 1.3. It can be
seen from Tables 1.2 and 1.3 that these catalogued pulsars are mostly located in the
Galactic System, their distance are from hundreds to tens of thousands of light years,
and their characteristic ages from tens of thousands to billions of years. Among
the discovered and catalogued pulsars, population of the pulsars with the emitting
signals in the optical or gamma-ray frequency bands is relatively few. There are
6 optical pulsars, including PSR B0531+21 (Crab Pulsar), PSR J0835–4510 (Vela
Pulsar), PSR B0540–69 (LMC), PSR B0656+14, PSR B0633+17 (Geminga) and
PSR B1509-58. There are around 100 gamma-ray pulsars, mostly discovered by the
Fermi Gamma-ray Space Telescope (FGST).