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Appendix A: Comparison with HiCIAO data

Figure A.1 shows the comparison between the azimuthally averaged radial profile of the polarised surface brightness at R′ and H band. The data are normalised to the maximum value at r> 0.2′′. By fitting a Gaussian profile to the ring emission (aexp [−(x − b)²/2c²] + d), the centre of the Gaussian is at ~61.5 ± 0.3 and ~64.8 ± 0.2 AU (for 145 pc distance) for R′ and H band, respectively. The width of the Gaussian is ~8.5 ± 0.4 and ~10.6 ± 0.9 AU for R′ and H band respectively. The errors are from the χ² minimisation and are much smaller than the spatial uncertainty from the observations (1 pixel size ~2 AU). Fitting a power-law to the brightness profile beyond the location of the peak, the emission drops as ∝ r^{− 2.92 ± 0.03} and ∝ r^{− 4.70 ± 0.06} for R′ and H band, respectively.

	Fig. A.1 Comparison between the azimuthally averaged radial profile of the polarised surface brightness at R′ and H band. The data are normalised to the maximum value at r> 0.2′′. Error bars are omitted for better readability; typical values are 40% and 30% of the mean value for R′ and H band respectively.
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Appendix B: Ring shape at different azimuthal cuts

Figure B.1 shows the radial profile of the azimuthally averaged surface brightness over four bins of PA. A Gaussian profile is fitted to each case; the width and centre of the Gaussians are summarised in Table B.1. The fitting results show that there are no significant azimuthal variations of the ring within the uncertainties of the data (pixel size ~2 AU).

	Fig. B.1 Radial profile of the polarised surface brightness obtained assuming four different cuts of the PA.
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© ESO, 2015