  The detection of gravitational waves with Pulsar Timing Arrays (PTAs)
requires precise measurement of the difference between the pulsars' timing
models and their observed pulses, as well as dealing with numerous and
sometimes hard to diagnose sources of noise. Outliers may have an impact on
this already difficult procedure, especially if the methods used are not robust
to such anomalous observations. Until now, no complete and practical
quantification of their effects on PTA data has been provided. With this work,
we aim to fill this gap. We corrupt simulated datasets featuring an increasing
degree of complexity with varying percentages of uniformly distributed outliers
and investigate the impact of the latter on the recovery of the injected
gravitational wave signals and pulsar noise terms. We found that the
gravitational waves signal, due to its expected correlation, is more robust
against these anomalous observations when compared to the other injected
processes. This result is especially relevant in the context of the emerging
statistical evidence for the gravitational wave background in PTA datasets,
further strengthening those claims.
