  Fast Radio Bursts (FRBs) are extremely energetic pulses of millisecond
duration and unknown origin. In order to understand the phenomenon that emits
these pulses, targeted and untargeted searches have been performed for
multi-wavelength counterparts, including the optical. The objective of this
work is to search for optical transients at the position of 8 well-localized
FRBs, after the arrival of the burst on different time-scales (typically at one
day, several months, and one year after FRB detection) in order to compare with
known transient optical light curves. We used the Las Cumbres Observatory
Global Telescope Network (LCOGT), which allows us to promptly take images owing
to its network of twenty-three telescopes working around the world. We used a
template subtraction technique on all the images we collected at different
epochs. We have divided the subtractions into two groups, in one group we use
the image of the last epoch as a template and in the other group we use the
image of the first epoch as a template. We have searched for bright optical
transients at the localizations of the FRBs (<1 arcsec) in the template
subtracted images. We have found no optical transients, so we have set limiting
magnitudes of optical counterparts. Typical limiting magnitudes in apparent
(absolute) magnitudes for our LCOGT data are ~22 (-19) mag in the r-band. We
have compared our limiting magnitudes with light curves of superluminous
supernovae (SLSNe), type Ia supernovae (SNe), supernovae associated with
gamma-ray bursts (GRB SNe), a kilonova, and tidal disruption events (TDEs). We
rule out that FRBs are associated with SLSN at a confidence of ~99.9%. We can
also rule out the brightest sub-types of type Ia SNe, GRB SNe and TDEs (under
some conditions) at similar confidence, though we cannot exclude scenarios
where FRBs are associated with the faintest sub-type of each of these transient
classes.
