  The aim of the current paper is to apply the method of Bambi (Bambi, 2015) to
a source which contains two or more simultaneous triads of variability
components. The joint chi-square variable that can be composed in this case,
unlike some previous studies, allows the goodness of the fit to be tested. It
appears that a good fit requires one of the observation groups to be
disregarded. Even then, the model prediction for the mass of the neutron star
in the accreting millisecond pulsar IGR J17511-3057 is way too high to be
accepted.
