Light Curves of Symbiotic Stars in Massive Photometric Surveys I: D-Type Systems

ASAS, MACHO, OGLE and SAAO JHKL light curves of 13 stars, that have at some time been classified as D-type symbiotic stars, are analyzed. Most of the near-IR light curves that have been monitored over many years show long-term changes due to variable dust obscuration, in addition to the stellar Pulsation. The distances to these objects are derived from the period-luminosity relation and estimates of the mass-loss rates made from the K-0 - [12] color. We reclassify AS 245 as an S-type symbiotic star with a semi-regular cool component and a pulsation period of about one year. The periods of the large amplitude pulsations of SS73 38 (463 days), AS 210 (423 days) and H2-38 (395 days) are estimated for the first time, confirming that they are symbiotic Miras. A comparison of the symbiotic Miras with normal Miras of similar pulsation period shows that the symbiotic stars have on average higher values of K-0 - [12]. This may indicate that they have higher mass-loss rates, or more likely that the dust which is being lost by the Mira is trapped within the binary system.