Artist's sketch of accreting neutron star, a possible source of gravitational waves. Image: NASA.
Millisecond pulsars are old neutron stars that has been spun up to a rotation period on the order of a millisecond. It is assumed that the spin-up mechanism can be an accretion of matter. Another fact is that millisecond pulsars are not spinning down very much, comparing to other pulsars, according to p-pdot diagram. Timing of radio-pulsars from these neutron stars is very precice. Pulsar Timing Arrays (PTAs) are setups of radio-observatories recording residuals from timing models of millisecond pulars. Cross-correlated timing residuals may indicate a presense of a stochastic gravitaitonal-wave background in the nHz band, and should include the gravitational-wave background from merging galaxies in the observable Universe.
This is short note about noise properties of PTA, and it will probably expand in the future.
|Measured "white" noise parameters of pulsars||Phenomenological "white" noise parameters|
|The above are factors that should be applied to uncertainty of arrival times (sigma_toa) in order to obtain a total white noise.||The above factors are physical sources of noise in PTA experiments.|
Useful dimensional relations in PTA
Strain power spectral density PSD ~ [s^3]*[strain^2]
Artist's representation of a GRB jets (NASA), and a 3D model of the Lomonosov satellite (MSU).