Difference in magnitudes between fainter and brighter components in band.

        :param band:
            Photometric bandpass.

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)