Detecting a Gravitational Wave Background using Angular Correlations in Millisecond Pulsar Timing Array Data
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**Session 36 -- Particle Astrophysics**
*Display presentation, Tuesday, 9:30-6:30, Pauley Room*

## [36.02] Detecting a Gravitational Wave Background using Angular Correlations in Millisecond Pulsar Timing Array Data

*Shauna Sallmen, D.C. Backer (Univ. of California at Berkeley), R. Foster (Naval Research Lab)*
A stochastic spectrum of gravitational wave background radiation (GBR) from
the early universe will produce unmodeled perturbations to the arrival
times of an array of millisecond pulsars. These perturbations will have
a set of distinct angular signatures that can be separated from other
effects such as clock noise and ephemeris errors.
We present a method for analyzing the angular correlations in pulsar timing
residuals in order to detect such radiation.

We construct a set of angular basis functions appropriate to the induced
angular correlations in pulsar timing residuals. Sinusoids are
used for the temporal basis functions. Using a simulated GBR
spectrum,
we artificially produce idealized timing residuals at the positions of pulsars,
including both the contributions at the solar system (correlated) and at
the individual pulsars (uncorrelated). Using our method, we consider the
success with which we can recover the input simulated GBR. The inevitable
noise due to the uncorrelated effects of the GBR at each pulsar limits this
method. In addition,
although there are only five instantaneous free parameters, we find that
${_>\atop^{\sim}} 9$ pulsars are required for reasonable results. The
choice of coordinate system orientation is a small effect. This method
is promising, but application to
unevenly sampled real data with uneven observational errors
will be complicated.

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