Observational Properties Of Pulsars

N'Diaye Maxime L3-PS

Introduction What are pulsars? What could we learn thanks to

pulsars?

Discution Subject Description of pulsars The different classes of pulsars Young pulsars and supernova

remnants Pulsars are tools for investigations

Description of Pulsars

Description of Pulsars celestial objects with an high

periodic pulse rotating neutron stars formed in

supernova explosions pulse period very stable, but not

constant

Description of Pulsars Extremly strong magnetic fields (up

to 10^15 G, 1G=10^11 Tesla) Pulsars generate electric fields of

10^12 V/cm. The youngest pulsar known have

1700 years.

Description of Pulsars Pulsars are detectable at radio,

optical, x-ray, and gamma ray wavelenghts.

About 1500 pulsars are known. We estimated that there is more

than 25000 potentially observable pulsars in the Galaxy.

Description of Pulsars

The different classes of Pulsars The rate of period increase and the

spin-down rate can be used to estimate the pulsar age and the magnetic field strength.

for example:P=1s, deriv(P)=10^-15 => 10^6 to 10^7 years and 10^12G

The different classes of Pulsars MSPs are pulsars with periods less

than 20 ms. They are also characterised by

less spin-down rate than other pulsars.

MSPs have ages of 10^9 to 10^10 years and magnetic fields of 10^8 to 10^9 G.

The different classes of Pulsars MSPs are extremely good clocks,

with a period stability rivaling that of the best terrestrial atomic clocks.

Magnetars are pulsars with high magnetic fields and periods from 6 to 10s.

The different classes of Pulsars The plot of pulsar period P versus

period derivative deriv(P) distinguishes the different classes of pulsars.

Young pulsars and supernova remnants Widely distributed across the

Galaxy But pulsars are founded in SNR

often enough that no astronomer doubts that pulsars are the remnant star of supernova explosion.

Young pulsars and supernova remnants But why all pulsars are not

associated with SNR?

Pulsars associated with SNR have short periods.

They are young pulsars.

Young pulsars and supernova remnants A pulsar is given a strong kick at

birth that propels it with velocities of 400 to 500 km/s.

In several tens of thousands of years, the pulsar emerges from the supernova nebula.

Old pulsars have time to move far away from SNR.

Pulsars are tools for investigations Supernova explosion, who form

pulsars, generaly leaves a SNR.So pulsars help astronomers to investigate properties of SNR.

Many pulsars are in interstellar medium.So they can be used to investigate interstellar medium properties.

Summary MSPs can be used as a clock. Pulsars mark the end-point of the

evolution of massive stars. Pulsars can be used like tools to

investigate the Galaxy.