2010ApJ...723..658O

We have performed a comprehensive chemical abundance analysis of the extremely metal-poor ([Ar/H] < -2) halo planetary nebula (PN) BoBn 1 based on International Ultraviolet Explorer archive data, Subaru/High-Dispersion Spectrograph spectra, VLT/UVES archive data, and Spitzer/IRS spectra. We have detected over 600 lines in total and calculated ionic and elemental abundances of 13 elements using detected optical recombination lines (ORLs) and collisionally excited lines (CELs). The estimations of C, N, O, and Ne abundances from the ORLs and Kr, Xe, and Ba from the CELs are done the first for this nebula, empirically and theoretically. The C, N, O, and Ne abundances from ORLs are systematically larger than those from CELs. The abundance discrepancies apart from O could be explained by a temperature fluctuation model, and that of O might be by a hydrogen-deficient cold component model. We have detected five fluorine and several slow neutron capture elements (the s-process). The amounts of [F/H], [Kr/H], and [Xe/H] suggest that BoBn 1 is the most F-rich among F-detected PNe and is a heavy s-process element rich PN. We have confirmed dust in the nebula that is composed of amorphous carbon and polycyclic aromatic hydrocarbons with a total mass of 5.8x10^–6 M_☉. The photoionization models built with non-LTE theoretical stellar atmospheres indicate that the progenitor was a 1-1.5 M_☉ star that would evolve into a white dwarf with an ∼0.62 M_☉ core mass and ∼0.09 M_☉ ionized nebula. We have measured a heliocentric radial velocity of +191.6 ±1.3 km/s and expansion velocity 2V_exp of 40.5±3.3 km/s from an average over 300 lines. The derived elemental abundances have been reviewed from the standpoint of theoretical nucleosynthesis models. It is likely that the elemental abundances except N could be explained either by a 1.5 M_☉ single star model or by a binary model composed of 0.75 M_☉+ 1.5 M_☉stars. Careful examination implies that BoBn 1 has evolved from a 0.75 M_☉+ 1.5 M _☉ binary and experienced coalescence during the evolution to become a visible PN, similar to the other extremely metal-poor halo PN, K 648 in M 15.