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Appendix A: Observation data

	Fig. A.1 Azimuthally averaged radial profiles of S Sct. Top: the first (dashed) and the re-observation (solid − adopted for the modelling) in the blue filter. Bottom: corresponding profiles in the red band.
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	Fig. A.2 OBSID 1342219068 and 1342219069 observation of S Sct in the blue band.
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	Fig. A.3 OBSID 1342229077 and 1342229078 observation of S Sct in the blue band. The field of view and scale are different from those of OD 705.
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In principle, a combination of all available HerschelPACS data (i.e. both observing dates) is desirable to recover the faintest structures as well as possible. There are, however, significant differences in the pointing between the first and the re-observation, which result in a smeared image if the datasets are combined uncorrected. A modification of the astrometric information is possible by hand, but the results are not fully satisfactory. In the case of RT Cap the use of only the better (i.e. higher signal-to-noise ratio) dataset is justified, since the addition of the much shorter observation (see, e.g., Cox et al. 2012) does not improve the final map noticeably. For S Sct the case is different, since both datasets have similar depths. Although the individual observations by themselves have very good signal-to-noise ratios, a combination of all available data does not reveal additional morphological information and does not give any benefits regarding the azimuthally averaged profiles used for modelling. Therefore we eventually used here only a single observation, OBSID 1342229077 and 1342229078, because of its better coverage resulting from the smaller scanned area at similar observing duration. A juxtaposition of the S Sct observations is given in the following.

Observations from both ODs were reduced using HIPE and mapped with Scanamorphos version 13, which means that the data processing and calibration can be assumed to be consistent (the full maps are shown in Figs. A.2  and A.3). However, the numbers in Table A.1 show some differences in the photometry. In the blue band the discrepancy is about 6%, in the red band it is 9%. While at 70 μm the observation taken on OD 705 suggests a higher flux than on OD 860, the situation is just the reverse for the 160 μm measurement. Nonetheless, the relative errors between the two bands more or less comply with the expected photometric accuracies. The largest uncertainty of the flux calibration is the background estimation performed by Scanamorphos. The differences shown in Fig. A.1, especially visible in the red, are partly caused by the varying background subtraction in the two cases. Considering the rather poor model fits to the brightness distribution of S Sct, the impact of the slightly different observed profiles on the modelling outcome is negligible.

Appendix B: Photometric data

© ESO, 2014