2020MNRAS.491.2959O

We performed detailed spectroscopic analyses of a young C-rich planetary nebula (PN) Jonckheere 900 (J900) in order to characterize the properties of the central star and nebula. Of the derived 17 elemental abundances, we present the first determination of eight elemental abundances. We present the first detection of the [F IV] 4059.9 Å, [F V] 13.4 µm, and [Rb IV] 5759.6 Å lines in J900. J900 exhibits a large enhancement of F and neutron-capture elements Se, Kr, Rb, and Xe. We investigated the physical conditions of the H2 zone using the newly detected mid-IR H2 lines while also using the previously measured near-IR H2 lines, which indicate warm (∼670 K) and hot (∼3200 K) temperature regions. We built the spectral energy distribution (SED) model to be consistent with all the observed quantities. We found that about 67 per cent of all dust and gas components (4.5 x 10-4 M☉ and 0.83 M☉, respectively) exists beyond the ionization front, indicating the critical importance of photodissociation regions in understanding stellar mass loss. The best-fitting SED model indicates that the progenitor evolved from an initially ∼2.0 M☉ star that had been in the course of the He-burning shell phase. Indeed, the derived elemental abundance pattern is consistent with that predicted by an asymptotic giant branch star nucleosynthesis model for a 2.0 M☉ star with Z = 0.003 and partial mixing zone mass of 6.0 x 10-3 M☉. Our study demonstrates how accurately determined abundances of C/F/Ne/neutron-capture elements and gas/dust masses help us understand the origin and internal evolution of the PN progenitors.