PN G054.2-03.4 light and velocity curves

We aim to understand the origins of the Necklace and its dwarf carbon central star. We study the carbon abundance of the nebula through far ultraviolet spectroscopy obtained with the Hubble Space Telescope.

Furthermore, through simultaneous modelling of multiband light and velocity curves, we attempt to constrain the parameters of the central star system. Puzzlingly, we find that the region of the inner nebula observed with the Hubble Space Telescope is seemingly not carbon- rich, at odds with the dwarf carbon star nature of the companion of the central star. The initial mass of the nebular progenitor was likely very close to the limit to become carbon-rich, perhaps experiencing a very late thermal pulse.