THE ORIGIN AND EVOLUTION OF THE HALO PN BoBn 1: FROM A VIEWPOINT OF CHEMICAL ABUNDANCES BASED ON MULTIWAVELENGTH SPECTRA

Abstract

We have performed a comprehensive chemical abundance analysis of the extremely metal-poor ([Ar/H]<-2) halo planetary nebula (PN) BoBn 1 based on IUE archive data, Subaru/HDS 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 5 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 PAHs with a total mass of 5.8×10 −6 M ⊙ . The photo-ionization 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 −1 and expansion velocity 2V exp of 40.5 ± 3.3 km s −1 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.

Heavy elements in planetary nebulae: A theorist's gold mine

“…Otsuka et al (2010). Furthermore, the high fluorine abundance of this PN ([F/H] = +1.39 compared to the predicted [F/H] = +0.86) is also consistent with the present day PN being the product of a star that has accreted material from a previous AGB companion of ∼1.5 M of low metallicity (see discussion in Otsuka et al 2010).…”

“…The new s-process predictions can be compared to the composition of the metal-poor PN BoBn 1 studied by Otsuka et al (2010). Otsuka et al (2010).…”

“…For example, the elemental 128 A. I. Karakas & M. Lugaro abundances of He, Ne, and Ar can be obtained, along with the abundances of C, N, O, S, and Cl, e.g., Henry et al (2010), Shaw et al (2010). It has also been shown that some PNe are enriched in heavy elements that can be produced by the s-process including Ge, Se, Kr, Xe, and Ba, e.g., Pequignot & Baluteau (1994), Dinerstein & Geballe (2001), Sharpee et al (2007), Sterling & Dinerstein (2008), Otsuka et al (2010). Sterling & Dinerstein (2008) obtained Se and Kr abundances for 120 Galactic PNe, and investigated trends between s-process enrichment and PN morphology and other nebular and stellar characteristics.…”

Atomic data for neutron-capture elements

“…Trans-iron element emission lines have been detected in objects ranging from planetary nebulae (e.g., Zhang et al 2005;Sharpee et al 2007;Sterling et al 2007;Sterling & Dinerstein 2008;Sterling et al 2009;Otsuka et al 2010Otsuka et al , 2011 to H II regions (e.g., Baldwin et al 2000;Blum & McGregor 2008, and references therein), and the interstellar medium of other galaxies (Vanzi et al 2008). Determinations of their abundances have important implications for the production and chemical evolution of n-capture nuclides in the Universe (e.g., Busso et al 1999;Sneden et al 2008;Sterling & Dinerstein 2008).…”

Stark halfwidth trends along the homologous sequence of doubly ionized noble gases

“…Electron temperature and abundances of planetary nebulae are obtained from Ar III spectral lines (Keenan et al 1988). Otsuka et al (2010) performed a comprehensive chemical abundance analysis of the planetary nebula BoBn 1. Among others, these authors used ultraviolet Ne III and visible Ar III spectral lines.…”