  Reliable low-latency gravitational wave parameter estimation is essential to
target limited electromagnetic followup facilities toward astrophysically
interesting and electromagnetically relevant sources of gravitational waves. In
this study, we examine the tradeoff between speed and accuracy. Specifically,
we estimate the astrophysical relevance of systematic errors in the posterior
parameter distributions derived using a fast-but-approximate waveform model,
SpinTaylorF2 (STF2), in parameter estimation with lalinference_mcmc. Though
efficient, the STF2 approximation to compact binary inspiral employs
approximate kinematics (e.g., a single spin) and an approximate waveform (e.g.,
frequency domain versus time domain). More broadly, using a large
astrophysically-motivated population of generic compact binary merger signals,
we report on the effectualness and limitations of this single-spin
approximation as a method to infer parameters of generic compact binary
sources. For most low-mass compact binary sources, we find that the STF2
approximation estimates compact binary parameters with biases comparable to
systematic uncertainties in the waveform. We illustrate by example the effect
these systematic errors have on posterior probabilities most relevant to
low-latency electromagnetic followup: whether the secondary is has a mass
consistent with a neutron star; whether the masses, spins, and orbit are
consistent with that neutron star's tidal disruption; and whether the binary's
angular momentum axis is oriented along the line of sight.
