SIMBAD references

We present a study of circumstellar dust properties in the symbiotic Miras RX Pup, V835 Cen, RR Tel and R Aqr, which show obscuration events during the observed time intervals. The obscuration events, as seen from the light curves corrected for Mira pulsations, have been investigated in view of the change of colors caused by the circumstellar dust. Assuming a spherical temperature distribution of the dust in the close neighborhood of the Mira, the DUSTY code was used to solve the radiative transfer in order to determine the dust temperature and its properties in each particular case. The preliminary results of this study provide information on the nature of the dust during the obscuration events.