Pulsars and relativity

1. Physics of neutron star interior 2. Radio pulsars a. Young pulsars b. Recycling pulsars c. Hulse-Taylor pulsar d. Double pulsar: probe of magnetosphere e. Double pulsar: relativity

3. Future prospects

Neutron stars: general-relativistic, super-magnetized, partly elastic giant nucleus containing several types of exotic quantum fluids.

First discovered neutron star: a radio pulsar.After 40 years, origin of the radio beam isnot understood. Hewish, Bell, et al 1968

Pulsars are excellent clocks… But only after averaging!

Credit: Ingrid Stairs

Magnetic field and period increase:

Pulsar spindownluminosity

(Spitkovsky 2007)

1 2

MagneticField (dipole)

Rotational phase

Dynamical simulations of the rotating magnetosphere

Spitkovsky 2007

Chandra image:

Crab nebula is powered by the pulsar spin-down.

Period vs Period derivative:

Normal pulsars

Recycled, millisecond pulsars

Period vs Period derivative:

Millisecond pulsars:

1. Spun up by accretion from companion. Highest spin 716 Hz (Hessel, et al 2006)

2. Accretion reduces magnetic field. B~100 million G.

Spin-up from a binary companion

• Low-mass x-ray binaries: Roche-Lobe overflow. Donor star is

a. Low-mass main-sequence star b. White dwarf c. Brown dwarf

• High-mass x-ray binaries: accretion from a fast wind of the high-mass companion.

Millisecond X-ray pulsar! Found by Wijnands & van der Klis 98.Spin-up by recycling prooved.

Using pulsars as Einstein clocks.

Hulse and Taylor found a binary NS, one of them a pulsar, in 1973.This Hulse-Taylor pulsar has been used for dramatic tests of GR.Nobel prize 1993.

ggg

Masses.

Shapiro delay

Gravitational Radiation. This is not a fit!Weisberg & Taylor 2004

Orbit shrinks due togravitational wave emission

Double pulsar, discovered in the Parkes Telescope multibeam survey.

Lyne et al. 03Icredibly lucky: edge on.Pulsar eclipses directly probe magnetosphere.New GR tests.

Double Pulsar: Tests of GR (courtesy M. Kramer)Kramer et al. in prep.

Slides on the double pulsar courtesy of Maxim Lyutikov.

Conclusions:

• Neutron stars show a variety of interesting phenomena, mostly related to its magnetic fields and environments

• Pulsars currently provide the most precise tests of GR

• Will discuss SKA later on.