2 General Relativity Measurements from Pulsars
59
Fig. 2.4 Graphical representation of the number of members of various classes of known pulsars.
The purple circle labelled PSR includes the entire pulsar population (as from the ATNF pulsar
catalogue v1.57). The blue circle labelled ExGal refers to pulsars discovered outside the Milky
Way (in the Magellanic Clouds). Binary pulsars are represented by the red circle labelled BIN.
Pulsars discovered in globular clusters are enclosed in the green circle labelled GC, whereas the
recycled pulsars are reported in the yellow MSP circle. Data are extracted from http://www.atnf.
csiro.au/research/pulsar/psrcat/ [1]
pulsars (see Sect. 2.3), located in the bottom-left corner of the P − ˙
P diagram
of Fig. 2.2, are of special interest: the short duration of their signals and the
extreme regularity of their pulsations, make them particularly useful for studying
the fundamental topics mentioned in Sect. 2.1.
2.2.2 Intermittent Pulsars
Among the NSs with pulsating radio emission, there is a well-known subclass:
the so-called nulling pulsars (first noticed by Backer [17]) in which the emission
appears to suddenly switch off for several pulse periods (e.g. the case displayed
in Fig. 2.5). The nulling fraction is very variable from pulsar to pulsar and the
mechanism beyond the disappearance of pulses is still a matter of debate.
In recent years, a handful of objects, dubbed intermittent pulsars, in a way similar
to nulling pulsars but more extreme, were discovered. These objects show a quite
peculiar behaviour: their pulsed radio emission, regular for intervals of time variable
59
Fig. 2.4 Graphical representation of the number of members of various classes of known pulsars.
The purple circle labelled PSR includes the entire pulsar population (as from the ATNF pulsar
catalogue v1.57). The blue circle labelled ExGal refers to pulsars discovered outside the Milky
Way (in the Magellanic Clouds). Binary pulsars are represented by the red circle labelled BIN.
Pulsars discovered in globular clusters are enclosed in the green circle labelled GC, whereas the
recycled pulsars are reported in the yellow MSP circle. Data are extracted from http://www.atnf.
csiro.au/research/pulsar/psrcat/ [1]
pulsars (see Sect. 2.3), located in the bottom-left corner of the P − ˙
P diagram
of Fig. 2.2, are of special interest: the short duration of their signals and the
extreme regularity of their pulsations, make them particularly useful for studying
the fundamental topics mentioned in Sect. 2.1.
2.2.2 Intermittent Pulsars
Among the NSs with pulsating radio emission, there is a well-known subclass:
the so-called nulling pulsars (first noticed by Backer [17]) in which the emission
appears to suddenly switch off for several pulse periods (e.g. the case displayed
in Fig. 2.5). The nulling fraction is very variable from pulsar to pulsar and the
mechanism beyond the disappearance of pulses is still a matter of debate.
In recent years, a handful of objects, dubbed intermittent pulsars, in a way similar
to nulling pulsars but more extreme, were discovered. These objects show a quite
peculiar behaviour: their pulsed radio emission, regular for intervals of time variable