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Abstract

We anticipate noise from the Laser Interferometer Space Antenna (LISA) will
exhibit nonstationarities throughout the duration of its mission due to factors
such as antenna repointing, cyclostationarities from spacecraft motion, and
glitches as highlighted by LISA Pathfinder. In this paper, we use a surrogate
data approach to test the stationarity of a time series, with the goal of
identifying noise nonstationarities in the future LISA mission. This will be
necessary for determining how often the LISA noise power spectral density (PSD)
will need to be updated for parameter estimation routines. We conduct a
thorough simulation study illustrating the power/size of various versions of
the hypothesis tests, and then apply these approaches to differential
acceleration measurements from LISA Pathfinder. We also develop a data analysis
strategy for addressing nonstationarities in the LISA PSD, where we update the
noise PSD over time, while simultaneously conducting parameter estimation, with
a focus on planned data gaps. We show that assuming stationarity when noise is
nonstationary leads to systematic biases and large posterior variances in
parameter estimates for galactic white dwarf binary gravitational wave signals.