  The motion of knots in astrophysical jets is commonly interpreted as shock
waves moving along it. Observations of the HST-1 knot during extended periods
of time have produced complicated light curves on many wavelengths which are
difficult to account using standard hydrodynamical models. Here we reproduce
these light curves using the semi-analytical approach developed by Mendoza et
al. (2009), developed to reproduce light curves of working surfaces moving
along relativistic jets. These working surfaces are generated by periodic
oscillations of the injected flow velocity and discharge at the base of the
jet. In particular, we use this approach to reproduce the exotic observed
features of the light curves of the HST-1 knot in M87. We show that the
complicated fits to the light curves are reproduced with high accuracy in all
wavelengths. As a bonus, we show that this model is also able to reproduce the
light curve of the micro-qsr A06200-00 with high accuracy.
