18
1 Introduction to the Pulsars
“Draugr” (PSR B1257+12A), “Poltergeist” (PSR B1257+12B) and “Phobetor” (PSR
B1257+12C), in which Draugr is the lowest mass planet, with a mass of 0.02 earthmasses, Poltergeist’s mass is 4.3 earth-masses, and Phobetor’s mass is 3.9 earthmasses. It is shown from theoretic analysis that these planets were formed by the
neutron star capturing matter from the remnants of the destroyed companion star.
Significance of PSR B1257+12 is not only to first discover pulsar’s planets, but also
the first planet system outside the solar system.
The millisecond pulsar, PSR B1937+21, is rotating roughly 641 times per second,
but another millisecond pulsar PSR J1748–2446ab, discovered in 2005, rotating 716
times a second. According to theories of neutron star structure and evolution, the
pulsars’ rotational speed limits can be estimated as follows:
(1) The spinning rates of pulsars would not be greater than 1500 cycles per second.
Otherwise, the pulsars would break apart [16].
(2) Pulsars would radiate the gravitational wave to further restrain their accelerated rotations before they spin at an extremely high speed. It is shown from
actual observational results that the spinning rates of pulsars seem to have been
controlled within 1000 cycles per second, corresponding a period of 1 ms.
By analyzing data from two spacecrafts, Rossi X-ray Timing Explorer (RXTE) and
International Gamma-Ray Astrophysics Laboratory (INTEGRAL), it was believed
in early 2007 that neutron star XTE J1739–285 was spinning at a rate of 1122 cycles
per second. However, this result is not statistically significant, only with a level
of 3 sigma significance, and has not also been obtained by other astronomers reanalyzing these data. Therefore, it is an interesting candidate for further observations,
but current results are inconclusive. Meanwhile, it is also believed that gravitational
radiation plays an import role in slowing down the rate of rotation. Additionally, the
accreting millisecond X-ray pulsar that spins at a rate of 599 cycles per second, IGR
J00291+5934 [17], will be a prime candidate for helping to detect the gravitational
waves in the future. Generally, most of such X-ray pulsars only spin at a rate of
around 300 cycles per second.
1.3.3 Spatial Distribution
With successfully launching a series of astronomical satellites in 1970s, the observational means of pulsars have been extended from the radio to infrared, visible,
ultraviolet, X-ray and gamma-ray bands of electromagnetic spectrum. As of 2020, a
population of the catalogued pulsars has gotten to 2811, in which most of pulsars are
the radio pulsars and concentrate on around the Galactic plane, and there are only
dozens of pulsars in the globular cluster. Although the pulsars located in out of the
Milky Way system have always been searched for a long time, there are only about
45 pulsars discovered in the LMC and SMC up to now [18]. Wherever pulsars are
in the Milky Way system or out, population of the discovered pulsars is far less than
that of the theoretically predicted ones. It is shown from theoretical estimations that
1 Introduction to the Pulsars
“Draugr” (PSR B1257+12A), “Poltergeist” (PSR B1257+12B) and “Phobetor” (PSR
B1257+12C), in which Draugr is the lowest mass planet, with a mass of 0.02 earthmasses, Poltergeist’s mass is 4.3 earth-masses, and Phobetor’s mass is 3.9 earthmasses. It is shown from theoretic analysis that these planets were formed by the
neutron star capturing matter from the remnants of the destroyed companion star.
Significance of PSR B1257+12 is not only to first discover pulsar’s planets, but also
the first planet system outside the solar system.
The millisecond pulsar, PSR B1937+21, is rotating roughly 641 times per second,
but another millisecond pulsar PSR J1748–2446ab, discovered in 2005, rotating 716
times a second. According to theories of neutron star structure and evolution, the
pulsars’ rotational speed limits can be estimated as follows:
(1) The spinning rates of pulsars would not be greater than 1500 cycles per second.
Otherwise, the pulsars would break apart [16].
(2) Pulsars would radiate the gravitational wave to further restrain their accelerated rotations before they spin at an extremely high speed. It is shown from
actual observational results that the spinning rates of pulsars seem to have been
controlled within 1000 cycles per second, corresponding a period of 1 ms.
By analyzing data from two spacecrafts, Rossi X-ray Timing Explorer (RXTE) and
International Gamma-Ray Astrophysics Laboratory (INTEGRAL), it was believed
in early 2007 that neutron star XTE J1739–285 was spinning at a rate of 1122 cycles
per second. However, this result is not statistically significant, only with a level
of 3 sigma significance, and has not also been obtained by other astronomers reanalyzing these data. Therefore, it is an interesting candidate for further observations,
but current results are inconclusive. Meanwhile, it is also believed that gravitational
radiation plays an import role in slowing down the rate of rotation. Additionally, the
accreting millisecond X-ray pulsar that spins at a rate of 599 cycles per second, IGR
J00291+5934 [17], will be a prime candidate for helping to detect the gravitational
waves in the future. Generally, most of such X-ray pulsars only spin at a rate of
around 300 cycles per second.
1.3.3 Spatial Distribution
With successfully launching a series of astronomical satellites in 1970s, the observational means of pulsars have been extended from the radio to infrared, visible,
ultraviolet, X-ray and gamma-ray bands of electromagnetic spectrum. As of 2020, a
population of the catalogued pulsars has gotten to 2811, in which most of pulsars are
the radio pulsars and concentrate on around the Galactic plane, and there are only
dozens of pulsars in the globular cluster. Although the pulsars located in out of the
Milky Way system have always been searched for a long time, there are only about
45 pulsars discovered in the LMC and SMC up to now [18]. Wherever pulsars are
in the Milky Way system or out, population of the discovered pulsars is far less than
that of the theoretically predicted ones. It is shown from theoretical estimations that