1999MNRAS.310L...1B

An optical spectrum of the Elson et al. candidate luminous white dwarf in the young LMC cluster NGC 1818 shows conclusively that it is not a degenerate star. A model atmosphere fit gives T_eff~31500K and logg~4.4, typical of a normal main-sequence B star. However, if it is a true LMC member then the star is underluminous by almost 3mag. Its position in the cluster colour-magnitude diagram also rules out the possibility that this is an ordinary B star. The luminosity is, however, consistent with a ∼0.5-M_☉ post-asymptotic giant branch or post-extended horizontal branch object, although if it has evolved via single-star evolution from a high-mass (7.6-9.0M_☉) progenitor then we might expect it to have a much higher mass, ∼0.9M_☉. Alternatively, it may have evolved in a close binary. In this case the object offers no implications for the maximum mass for white dwarf progenitors, or the initial-final mass relation. Finally, we suggest that it could in fact be an evolved member of the LMC disc, and merely projected by chance on to NGC 1818. Spectroscopically, though, we cannot distinguish between these evolutionary states without higher resolution (echelle) data.