2003MNRAS.343...67G

Improved light curves extracted from the MACHO data base are used to discuss the periods and amplitudes of the calibrating stars of the Mira P -L relations. Previously unpublished spectral types and positions are given for several of those that lie in the S Dor variable star field. It is found that the periods derived from the discovery observations were generally sufficiently accurate that the K - and m_bol-logP relations are not significantly changed by the MACHO results. Furthermore, the periods have remained essentially constant over two to three decades. The MACHO r -band amplitudes of the oxygen-rich Large Magellanic Cloud (LMC) Miras are similar to those in galactic (Baade's window) fields at a given period but there appear to be more shorter-period stars as a proportion of the whole than in the galaxy. In O-rich stars, the distinction in amplitude between the Miras and the semiregulars is not as conspicuous at shorter periods (<200 d) as at longer ones. The LMC carbon Miras have smaller amplitudes than their O-rich counterparts. Of the six stars with P > 420 d that were found to be too luminous to fit the P -L relation, two are now known to be Li-rich. This tends to confirm the suggestion that they are hot-bottom burners.