Observational Properties Of Pulsars N'Diaye Maxime L3-PS

Introduction n What are pulsars? n What could we learn thanks to pulsars?

Discution Subject n Description of pulsars n The different classes of pulsars n Young pulsars and supernova remnants n Pulsars are tools for investigations

Description of Pulsars

n celestial objects with an high periodic pulse n rotating neutron stars formed in supernova explosions n pulse period very stable, but not constant

Description of Pulsars n Extremly strong magnetic fields (up to 10^15 G, 1G=10^11 Tesla) n Pulsars generate electric fields of 10^12 V/cm. n The youngest pulsar known have 1700 years.

Description of Pulsars n Pulsars are detectable at radio, optical, x-ray, and gamma ray wavelenghts. n About 1500 pulsars are known. n We estimated that there is more than potentially observable pulsars in the Galaxy.

Description of Pulsars

The different classes of Pulsars n The rate of period increase and the spin-down rate can be used to estimate the pulsar age and the magnetic field strength. n for example: P=1s, deriv(P)=10^-15 => 10^6 to 10^7 years and 10^12G

The different classes of Pulsars n MSPs are pulsars with periods less than 20 ms. n They are also characterised by less spin-down rate than other pulsars. n 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 n MSPs are extremely good clocks, with a period stability rivaling that of the best terrestrial atomic clocks. n Magnetars are pulsars with high magnetic fields and periods from 6 to 10s.

The different classes of Pulsars n The plot of pulsar period P versus period derivative deriv(P) distinguishes the different classes of pulsars.

Young pulsars and supernova remnants n Widely distributed across the Galaxy n 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 n But why all pulsars are not associated with SNR? n Pulsars associated with SNR have short periods. n They are young pulsars.

Young pulsars and supernova remnants n A pulsar is given a strong kick at birth that propels it with velocities of 400 to 500 km/s. n In several tens of thousands of years, the pulsar emerges from the supernova nebula. n Old pulsars have time to move far away from SNR.

Pulsars are tools for investigations n Supernova explosion, who form pulsars, generaly leaves a SNR. So pulsars help astronomers to investigate properties of SNR. n Many pulsars are in interstellar medium. So they can be used to investigate interstellar medium properties.

Summary n MSPs can be used as a clock. n Pulsars mark the end-point of the evolution of massive stars. n Pulsars can be used like tools to investigate the Galaxy.