SPECKLE MASKING OBSERVATIONS OF R-64, THE DENSE STELLAR CORE OF THE OB-ASSOCIATION LH9 IN THE LARGE MAGELLANIC CLOUD

We present speckle masking observations of R 64 (= HD 32228; O9.5II: WC5), the central object of the OB association LH9 in the Large Magel lanic Cloud. Two sets of speckle interferograms were taken to select t he Johnson V spectral band and the strong Wolf-Rayet emission lines be tween 450 and 490 nm. In the 6''.4 x 6''.4 field of view 25 stellar co mponents were detected in R 64 with V magnitudes in the range 12.5 to 17.1 and down to a resolution of 0''.12. The brightest star in the vis ual component B is the only Wolf-Rayet star in R 64. The colour-magnit ude diagram of LH9, completed with the components of R 64, serves for the discussion of the evolutionary state of the association. There is evidence that the outer regions of LH9 are its youngest parts with an upper age of about 5 Myr, in accordance with estimates by Walborn & Pa rker (1992). The WC5 star in the centre is most likely the product of mass exchange in a massive close binary system with an age in excess o f 5 Myr. The mass density in R 64 is about 250 M.pc(-3) for stars more massive than 5 M..