millisecond pulsars

millisecond pulsars

A class of pulsars that produce pulses with a period of only a few milliseconds, and are thus neutron stars rotating hundreds of times per second. Unlike the fast ‘normal’ pulsars (e.g. the Crab and Vela pulsars), the millisecond pulsars' fast rotation is not a result of youth; they have almost certainly been ‘spun up’ by mass transfer in a close binary star at an earlier evolutionary stage. Rapid rotation of a neutron star is normally slowed precipitously because the star's strong magnetic field radiates away the rotational energy, as with the Crab pulsar (see Crab nebula); the millisecond pulsars detected so far, however, have only a very gradual rate of slowing down, probably because their magnetic fields are comparatively weak (104–105 tesla).

PSR 1937+21 was the first millisecond pulsar to be found, 1982, and is currently the fastest known (period 1.56 ms, i.e. 642 rotations per second). The second to be found, PSR 1953+29 (6.1 ms), is a member of a binary pulsar system; it orbits its unseen companion in 120 days. The old but rapidly spinning binary pulsar PSR 1913+16 also belongs in this class, although its period is rather longer (59 ms).

Recent surveys have discovered large numbers of millisecond pulsars in globular clusters; more than half are close binary pulsars. It is generally believed that most of the single millisecond pulsars were initially members of binary systems, but lost their companion stars either because of a stellar collision (which is possible in globular clusters) or because the radiation emitted by the pulsars completely destroyed, or ‘evaporated’, the companion stars (see black-widow pulsars). One millisecond pulsar (PSR 1257+12) appears to be orbited by two planet-mass objects (see planet pulsar).

References in periodicals archive ?
A major goal for the new instrument is to find and monitor millisecond pulsars, whose minute variations help measure the low-frequency hum of gravitational waves suffusing the universe.
The new study is the work of researchers from the Australian National University (ANU), who had a working hypothesis 6 the signal came from millisecond pulsars, which are thousands of rapidly spinning neutron stars.
But some, called millisecond pulsars, rotate hundreds of times faster.
Taylor Jr., "Millisecond pulsars: Nature's most stable clocks," Proceedings of the IEEE, vol.
A population of gamma-ray millisecond pulsars seen with the Fermi Large Area Telescope.
Observations and modeling of the companions of short period binary millisecond pulsars: Evidence for high-mass neutron stars.
While young pulsars usually appear in isolation, more than half of millisecond pulsars occur in binary systems, which suggested an explanation for their rapid spin.
Their study can also help explain an increasing number of observed binary millisecond pulsars which seem to require a triple system origin.
[44], it can be clearly obtained that the noise level increases with the increasing of the pulsar period P, going from some nanoseconds for millisecond pulsars to few millisecond, for pulsars with periods of the order of a second or a bit less than one second.
Prof Lyne then considered the creation of binary pulsar systems and millisecond pulsars, objects rotating so rapidly that the pulse of radiation from the star occurs hundreds of times a second.
"We currently have about 20 millisecond pulsars, but only five of these can be timed to the needed precision," he notes.
Other such millisecond pulsars (those that turn in the range of a thousandth of a second) have been discovered since.