docs: def dmag(self, band):
          """
          Difference in magnitudes between fainter and brighter components in band.
  
          :param band:
              Photometric bandpass.
  
          """
          m1 = self.stars['{}_mag_A'.format(band)]
          m2 = addmags(self.stars['{}_mag_B'.format(band)],
                       self.stars['{}_mag_C'.format(band)])
          return np.abs(m2-m1)