SIMBAD references

We present optical and infrared photometry, and optical polarimetry, of several pre-main sequence stars; much of the data were obtained quasi-simultaneously. Our data demonstrate that, while a simple occultation model for deep visual minima in pre-main sequence stars is consistent with the data in some cases, in others a major change in the outer dust shell is required to account for the optical-infrared behaviour. Apart from the marginal case of UX Ori, there is no significant correlation between polarization and photometric colours. We tentatively report the possible detection of circular polarization in AK Sco, RU Lup, HD97048 and HD144667.