Publications of the MPIfR Optical & Infrared
Interferometry Group
D. Schertl, K.-H. Hofmann, W. Seggewiss, und G.
Weigelt
Speckle masking observations of R 64, the dense stellar core of the
OB association LH9 in the Large Magellanic Cloud*
Astronomy and Astrophysics, 302, 327-334 (1995)
Abstract
We present speckle masking observations of R 64 (=HD 32228; O9.5II: +
WC5), the central object of the OB association LH9 in the Large
Magellanic Cloud. Two sets of speckle interferograms were taken to
select the Johnson V spectral band and the strong Wolf-Rayet emission
lines between 450 and 490nm. In the 6.4"x6.4" field of view 25 stellar
components 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
visual
component B is the only Wolf-Rayet star in R 64. The colour-magnitude
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 5Myr, in accordance with estimates by Walborn &
Parker (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 of
5Myr. The mass density in R 64 is about 250Msun_pc^-3^ for
stars more massive than 5Msun_.
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