Pulsar Timing

Time of arrival

Pulsar Timing

Model for expected arrival times incorporates:

spin-down, solar system orbits, pulsar velocity, pulsar orbits

Timing Residuals = Measured – Expected Pulse Arrival Times

Pulsar Timing

One year from today, the spin period will be

5.75745194393018(1) milliseconds

On our 50th wedding anniversary, it will be

5.75745201913820(6) milliseconds

Today at 7:45 pm, the spin period is 5.75745194212336(1) milliseconds

Pulsar Timing

Applications

What are gravitational waves?

1993 Nobel Prize

Existence of Gravitational Waves

Laser Interferometer Gravitational Wave Observatory (LIGO)

f ~ 1/ms (100 – 1000 Hz)

How can we detect them with pulsars?

f ~ 1/yrs (10-8 – 10-9 Hz)

Earth

Pulsar

Effect of a gravitational wave on pulsar residuals

For a 50 billion solar mass black hole binary at a distance of 200 million light years.

A Pulsar Timing Array

The Expected Correlation

The Expected Correlation

The Expected Correlation

The Expected Correlation

NANOGrav (North American Nanohertz Observatory for Gravitational Waves)

22 members from North America nanograv.org

Current Observations

< 100 ns RMS!

26 pulsars being timed with the Green Bank and Arecibo telescopes. Root-mean-square residuals from 100 ns to 1.5 μs.

How close are we?

The International Pulsar Timing Array (IPTA)

What will we see?

Detection of gravitational waves will be transformational!

We will no longer be limited to photons!

NOAO/AURA/NSF NOAO/AURA/NSF

Cambridge Cosmology Group