1.3 The Name, Classification and Distribution
13
by the letter “B” and “J”; for the pulsars discovered after 1993, it is regulated that
only J2000.0 can be used to name the pulsars. In other words, the naming rule of
the pulsars discovered after 1993 is “PSR Jrrrrsdddd”, where the last two digits
“dd” are expressed in arc-minutes, and other signs are as same as the above. For
example, the first pulsar discovered in 1968 can be named PSR B1919+21 using
epoch B1950.0, and also PSR J1921+2153 using epoch J2000.0; it is worth noting
that PSR J1921+2153 stands for the right ascension of 19h21min and the declination
of +21º53
. In 1993, a nearby binary millisecond pulsar was discovered in the Parkes
70 m survey [12] and named PSR J0437–4715, where only epoch J2000.0 can be
used, the right ascension expressed as 4h37min and the declination as −47º15
. PSR
J0437–4715 is the brightest and most stable in all known millisecond pulsars.
The naming of X-ray sources or X-ray pulsars is not normalized like the above
radio pulsars. In 1948, X-rays radiated from the Sun was first discovered by the
sounding rocket; in 1962, the X-ray source outside the solar system was successfully
detected by the sounding rocket with an altitude of 230 km; and then, dozens of X-ray
sources were also detected successively by the sounding rockets and balloons outside
the dense atmosphere. For early discovered X-ray sources, they were named by their
constellations as well as their discovery sequence in the same constellation. The
first X-ray source outside the solar system came from the constellation of Scorpius,
and thereby it was named Scorpius X-1 (or simply Sco X-1). Moreover, other X-ray
sources are also named similarly, such as Cygnus X-1, Cygnus X-2, Hercules X-1,
Centaurus X-3, LMC X-4 and SMC X-3, where LMC and SMC are acronyms, and
respectively Large Magellanic Cloud and Small Magellanic Cloud.
The first dedicated X-ray astronomy satellite, Uhuru, was launched successfully
from the Italian San Marco launch platform near Mombasa in Kenya on December 12,
1970. “Uhuru” is the Swahili word for “Freedom”. The satellite had been operated
by the U.S. National Astronautics and Space Administration (NASA), and X-ray
sources had been explored using it on the Earth orbit from 1970 to 1973. After
launching Uhuru, X-ray sources have often been named by initials of the satellite’s
names first discovering them, as well as their position parameters in which the right
ascension is expressed with hours and the declination with degrees. For example, “A”
stands for the satellite Aril-5, “S” for SAS-3, “E” for Einstein, “EXO” for EXOSAT,
“V” for Vela, as well as “U” for Uhuru in which 3U and 4U respectively denote the
third and fourth X-ray source catalogues from the satellite Uhuru.
1.3.2 Fundamental Classification
Currently, the signals emitted from pulsars have been observed in the radio, infrared,
visible, ultraviolet, X-ray and gamma-ray bands of the electromagnetic spectrum.
However, it is shown from the actual observations that most of the pulsars radiate the
signals only in the radio and X-ray bands, while a few pulsars in the infrared, visible,
ultraviolet and gamma-ray bands. According to the different frequency band ranges
of the signals radiated from pulsars, the pulsars can be classified into radio, optical,
13
by the letter “B” and “J”; for the pulsars discovered after 1993, it is regulated that
only J2000.0 can be used to name the pulsars. In other words, the naming rule of
the pulsars discovered after 1993 is “PSR Jrrrrsdddd”, where the last two digits
“dd” are expressed in arc-minutes, and other signs are as same as the above. For
example, the first pulsar discovered in 1968 can be named PSR B1919+21 using
epoch B1950.0, and also PSR J1921+2153 using epoch J2000.0; it is worth noting
that PSR J1921+2153 stands for the right ascension of 19h21min and the declination
of +21º53
. In 1993, a nearby binary millisecond pulsar was discovered in the Parkes
70 m survey [12] and named PSR J0437–4715, where only epoch J2000.0 can be
used, the right ascension expressed as 4h37min and the declination as −47º15
. PSR
J0437–4715 is the brightest and most stable in all known millisecond pulsars.
The naming of X-ray sources or X-ray pulsars is not normalized like the above
radio pulsars. In 1948, X-rays radiated from the Sun was first discovered by the
sounding rocket; in 1962, the X-ray source outside the solar system was successfully
detected by the sounding rocket with an altitude of 230 km; and then, dozens of X-ray
sources were also detected successively by the sounding rockets and balloons outside
the dense atmosphere. For early discovered X-ray sources, they were named by their
constellations as well as their discovery sequence in the same constellation. The
first X-ray source outside the solar system came from the constellation of Scorpius,
and thereby it was named Scorpius X-1 (or simply Sco X-1). Moreover, other X-ray
sources are also named similarly, such as Cygnus X-1, Cygnus X-2, Hercules X-1,
Centaurus X-3, LMC X-4 and SMC X-3, where LMC and SMC are acronyms, and
respectively Large Magellanic Cloud and Small Magellanic Cloud.
The first dedicated X-ray astronomy satellite, Uhuru, was launched successfully
from the Italian San Marco launch platform near Mombasa in Kenya on December 12,
1970. “Uhuru” is the Swahili word for “Freedom”. The satellite had been operated
by the U.S. National Astronautics and Space Administration (NASA), and X-ray
sources had been explored using it on the Earth orbit from 1970 to 1973. After
launching Uhuru, X-ray sources have often been named by initials of the satellite’s
names first discovering them, as well as their position parameters in which the right
ascension is expressed with hours and the declination with degrees. For example, “A”
stands for the satellite Aril-5, “S” for SAS-3, “E” for Einstein, “EXO” for EXOSAT,
“V” for Vela, as well as “U” for Uhuru in which 3U and 4U respectively denote the
third and fourth X-ray source catalogues from the satellite Uhuru.
1.3.2 Fundamental Classification
Currently, the signals emitted from pulsars have been observed in the radio, infrared,
visible, ultraviolet, X-ray and gamma-ray bands of the electromagnetic spectrum.
However, it is shown from the actual observations that most of the pulsars radiate the
signals only in the radio and X-ray bands, while a few pulsars in the infrared, visible,
ultraviolet and gamma-ray bands. According to the different frequency band ranges
of the signals radiated from pulsars, the pulsars can be classified into radio, optical,