2019MNRAS.482.2354O

We perform a detailed analysis of the fullerene C₆₀-containing planetary nebula (PN) SaSt2-3 to investigate the physical properties of the central star (B0-1II) and nebula based on our own Subaru/HDS spectra and multiwavelength archival data. By assessing the stellar absorption, we derive the effective temperature, surface gravity, and photospheric abundances. For the first time, we report time variability of the central star's radial velocity, strongly indicating a binary central star. Comparison between the derived elemental abundances and those predicted values by asymptotic giant branch (AGB) star nucleosynthesis models indicates that the progenitor is a star with initial mass of ∼1.25 M_☉ and metallicity Z = 0.001/α-element/Cl-rich ([α,Cl/Fe] ∼ +0.3-0.4). We determine the distance (11.33 kpc) to be consistent with the post-AGB evolution of 1.25 M_☉ initial mass stars with Z = 0.001. Using the photoionization model, we fully reproduce the derived quantities by adopting a cylindrically shaped nebula. We derive the mass fraction of the C-atoms present in atomic gas, graphite grain, and C₆₀. The highest mass fraction of C₆₀ (∼0.19 per cent) indicates that SaSt2-3 is the C₆₀-richest PN amongst Galactic PNe. From comparison of stellar/nebular properties with other C₆₀ PNe, we conclude that the C₆₀ formation depends on the central star's properties and its surrounding environment (e.g. binary disc), rather than the amount of C-atoms produced during the AGB phase.