  Ultralight bosons are a class of hypothetical particles that could
potentially solve critical problems in fields ranging from cosmology to
astrophysics and fundamental physics. If ultralight bosons exist, they form
clouds around spinning black holes with sizes comparable to their particle
Compton wavelength through superradiance, a well-understood classical wave
amplification process that has been studied for decades. After these clouds
form, they dissipate and emit continuous gravitational waves through the
annihilation of ultralight bosons into gravitons. These gravitons could be
detected with ground-based gravitational-wave detectors using continuous-wave
searches. However, it is conceivable for other continuous-wave sources to mimic
the emission from the clouds, which could lead to false detections. Here we
investigate how one can use continuous waves from clouds formed around known
merger remnants to alleviate this problem. In particular, we simulate a
catalogue of merger remnants that form clouds around them and demonstrate with
select "golden" merger remnants how one can perform a Bayesian
cross-verification of the ultralight boson hypothesis that has the potential to
rule out alternative explanations. Our proof-of-concept study suggest that, in
the future, there is a possibility that a merger remnant exists close enough
for us to perform the analysis and test the boson hypothesis if the bosons
exist in the relevant mass range. Future research will focus on building more
sophisticated continuous-wave tools to perform this analysis in practice.
