IVth School of Astroparticle Physics
May 27th - June 1st, 2013
OHP, Saint Michel l'Observatoire

Gravitational Waves

Pulsars as a tool for test of strong gravity

Jérôme PÉTRI
Observatoire Astronomique de Strasbourg

The aim of this lecture is to present our current understanding about the 2000 pulsars detected so far. We will mention in particular their application as very high precision cosmic clocks. Compact objects are of rich physical and astrophysical interest on their own, pulsars are useful tools to diagnose the galactic and interstellar medium. Although the origin of the pulsar emission mechanism remains largely unsolved, their impressive temporal stability enables us to use them as high precision clocks. This property is especially interesting for timing techniques opening the possibility to detect gravitational waves and more generally to test theories of gravity in the strong field regime.
  1. The pulsar phenomenon
    1. radio emission
    2. high energy emission
    3. orders of magnitude
    4. phenomenology
  2. The pulsar magnetosphere
    1. overview
    2. emission models
  3. Pulsars as a tool for detection
    1. survey of the Milky Way
    2. detection of planets
    3. equation of state of supra-nuclear matter
    4. detection of gravitational waves
  4. Tests of relativistic gravity
    1. timing relativistic binaries
    2. the binary pulsar PSR~B1913+16
    3. the double pulsar PSR~J0737-3039
  5. Perspectives


Although they have been discovered more than 40 years ago, pulsars remain enigmatic compact objects. This lecture summarizes our current knowledges about pulsars from an observational point of view as well as from a theoretical one.

In a first part, we remind some basic observational facts in order to fix the orders of magnitude (neutron star radius, rotation rate, magnetic field, spin down luminosity) and give some properties of their spectra, from the radio wavelengths to X-rays and gamma-rays.

In a second part, we review some models for pulsar magnetospheres which predict the launch of a relativistic wind. We will give an overview of the whole system, from the neutron star surface up to the surrounding nebula.

In a third part, we will show that pulsars help to map electrons in the Milky Way as well as the galactic magnetic field. The high precision pulsar timing allowed the detection of the first extrasolar planet around a pulsar and indirectly demonstrated the existence of gravitational waves.

In a last part, we show how to constrain theories of relativistic gravitation from the observation of neutron stars in binary systems containing one or even two pulsars. We will discuss in more details the exceptional case of the double pulsar PSR~J0737-3039 for which the masses of the two neutron stars have been measured with great accuracy. These observations agree with the predictions of general relativity.

  • Books
    • Theory of Neutron Star Magnetospheres, F.C. Michel, University of Chicago Press, 1991.
    •  Physics of the Pulsar Magnetosphere, A.V. Gurevich, V.S. Beskin & Ya.N. Istomin, Cambridge University Press, 2006.
    • Rotation and Accretion Powered Pulsars, Pranab Ghosh, World Scientific Publishing Company, 2007.
    • Pulsar Astronomy, A. Lyne & F. Graham-Smith, Cambridge University Press, 2006.
    • Handbook of Pulsar Astronomy, D. Lorimer & M. Kramer, Cambridge University Press, 2004.
  • Reviews
    • The Double Pulsar, M. Kramer & I. Stairs, ARA&A, 2008, 46, 541-572.
    • Testing General Relativity with Pulsar Timing, I. Stairs, Living Reviews in Relativity, 2003, 6, 5.
    • The double pulsar system: a unique laboratory for gravity, Kramer M. & Wex N., Classical and Quantum Gravity, 2009, 26, 073001.


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