1.4 The Physical Mechanisms and Characteristics
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1.4.5 Formation Processes
On the formation processes of pulsars, it is generally accepted that the solid supernova
remnants are produced by the supernova explosions of massive stars, and thus the
proto neutron stars will be formed in the centers of these remnants. The proto neutron
stars bring up gradually the theoretically predicted neutron stars after they undergo
the gravitational collapses and the phase transitions. However, by comparing the
discovered more than 200 supernova remnants with the catalogued more than 2800
pulsars, it is shown that there are only tens of the counterparts each other. And thus,
the above interpretation on the formation processes of pulsars will be suspected
inevitably.
At present, most scholars still insist that pulsars result from the supernova explosions. Their reasons are: on the one hand, the pulsars corresponding to the supernova
remnants can not be observed as their radiation beams do not sweep through the nearEarth space; on the other hand, all remnants of the supernova explosions are spread
so rapidly out space that their spatial densities are too low to have been observed,
and thereby the pulsars whose counterparts of the supernova explosion remnants is
not found, are actually the counterparts of the diffused remnants.
Meanwhile, some scholars also believe that the supernova explosion is not unique
approach to bring up neutron stars. For example, when the mass of a white dwarf by
accreting matter is more than the Chandrasekhar limit, the white dwarf will gradually
form a neutron star by the gravitational collapse and the phase transition. Obviously,
the formation processes of pulsars still need to be studied further.
1.5 The Observational Features
1.5.1 Pulse Profiles
Pulse profile is a periodic change curve that the intensity of the signals emitted from
the pulsar varies with time, also called light curve. The profile of each pulsar is
unique identifier, a representation of the features of pulsars, which is determined by
the internal mechanism of pulsars and the external space environment. The pulse
profiles vary in terms of shape, size, cycle’s length, and intensity. Some basic physical parameters can be obtained by the pulse profiles, such as pulse period, pulse
amplitude, total number of pulse peaks, and stability of pulse period. Most of the
discovered pulsars emit the periodic pulsation signals in the wider bands of radio
frequencies; the pulse widths are about one thirtieth of the entire periods; the pulse
shapes in millisecond timescale are very complicated. A typical pulse profile usually
includes one main pulse signal, as well as one or more sub-pulse signals. The structures of the sub-pulse signals are more complex and their timescales even get to
an order of microseconds. In other words, the single pulse radiation of pulsars has
very high polarization characteristics; the pulse intensities and shapes are different
29
1.4.5 Formation Processes
On the formation processes of pulsars, it is generally accepted that the solid supernova
remnants are produced by the supernova explosions of massive stars, and thus the
proto neutron stars will be formed in the centers of these remnants. The proto neutron
stars bring up gradually the theoretically predicted neutron stars after they undergo
the gravitational collapses and the phase transitions. However, by comparing the
discovered more than 200 supernova remnants with the catalogued more than 2800
pulsars, it is shown that there are only tens of the counterparts each other. And thus,
the above interpretation on the formation processes of pulsars will be suspected
inevitably.
At present, most scholars still insist that pulsars result from the supernova explosions. Their reasons are: on the one hand, the pulsars corresponding to the supernova
remnants can not be observed as their radiation beams do not sweep through the nearEarth space; on the other hand, all remnants of the supernova explosions are spread
so rapidly out space that their spatial densities are too low to have been observed,
and thereby the pulsars whose counterparts of the supernova explosion remnants is
not found, are actually the counterparts of the diffused remnants.
Meanwhile, some scholars also believe that the supernova explosion is not unique
approach to bring up neutron stars. For example, when the mass of a white dwarf by
accreting matter is more than the Chandrasekhar limit, the white dwarf will gradually
form a neutron star by the gravitational collapse and the phase transition. Obviously,
the formation processes of pulsars still need to be studied further.
1.5 The Observational Features
1.5.1 Pulse Profiles
Pulse profile is a periodic change curve that the intensity of the signals emitted from
the pulsar varies with time, also called light curve. The profile of each pulsar is
unique identifier, a representation of the features of pulsars, which is determined by
the internal mechanism of pulsars and the external space environment. The pulse
profiles vary in terms of shape, size, cycle’s length, and intensity. Some basic physical parameters can be obtained by the pulse profiles, such as pulse period, pulse
amplitude, total number of pulse peaks, and stability of pulse period. Most of the
discovered pulsars emit the periodic pulsation signals in the wider bands of radio
frequencies; the pulse widths are about one thirtieth of the entire periods; the pulse
shapes in millisecond timescale are very complicated. A typical pulse profile usually
includes one main pulse signal, as well as one or more sub-pulse signals. The structures of the sub-pulse signals are more complex and their timescales even get to
an order of microseconds. In other words, the single pulse radiation of pulsars has
very high polarization characteristics; the pulse intensities and shapes are different