code: def nu_max(self, *args):
          
          return 3120.* (self.mass(*args) /
                          (self.radius(*args)**2 * np.sqrt(self.Teff(*args)/5777.)))
docs: Returns asteroseismic nu_max in uHz
  
          reference: https://arxiv.org/pdf/1312.3853v1.pdf, Eq (3)