1996A&A...308..489K

Semiregular variables of type SRa and SRb are studied by fitting combinations of blackbodies to new near infrared and IRAS data. The fitted parameters T^*, T^d and R^d/R^* are related to physically meaningful quantities. For the O-rich cases all `blue' objects can be reasonably well approximated by only one blackbody whereas the `red' and the `Mira' SRVs need two. The T<sup>*</sup> values, reflecting mainly offsetted (-500K), effective temperatures for objects with small to moderate mass loss, are significantly higher in the `blue' SRV cases. A small difference between the T^* distributions of `red' and `Mira' SRVs seems to be present: with a few exceptions most of the `Mira' T<sup>*</sup> values are concentrated in the cold half of the `red' SRV distribution. Carbon-rich objects differ significantly from the O-rich ones in their fit parameters. Sometimes `unphysically' low T^* are found - a result of circumstellar reddening in the high mass loss cases. Also lower values of T^d, accompanied by normal T^*s and large shell radii are common. S-stars populate a similar region as the optically thin carbon stars.