Finding sound shells in LISA mock data using likelihood sampling
  We study to what extend LISA can observe features of gravitational wave
spectra originating from cosmological first-order phase transitions. We focus
on spectra which are of the form of double-broken power laws. These spectra are
predicted by hydrodynamic simulations and also analytical models such as the
sound shell model. We argue that the ratio of the two break frequencies is an
interesting observable since it can be related to the wall velocity while
overall amplitude and frequency range are often degenerate for the numerous
characteristics of the phase transition. Our analysis uses mock data obtained
from the power spectra predicted by the simplified simulations and the sound
shell model and analyzes the detection prospects using $\chi^2$-minimization
and likelihood sampling. We point out that the prospects of observing two break
frequencies from the electroweak phase transition is hindered by a shift of the
spectrum to smaller frequencies for strong phase transitions. Finally, we also
highlight some differences between signals from the sound shell model compared
to simulations.
