Chemical compositions and plasma parameters of planetary nebulae with Wolf-Rayet and wels type central stars

Abstract

Aims. Chemical compositions and other properties of planetary nebulae around central stars of spectral types [WC], [WO], and wels are compared with those of "normal" central stars, in order to clarify the evolutionary status of each type and their interrelation. Methods. We use plasma diagnostics to derive from optical spectra the plasma parameters and chemical compositions of 48 planetary nebulae. We also reanalyze the published spectra of a sample of 167 non-WR PN. The results as well as the observational data are compared in detail with those from other studies of the objects in common. Results. We confirm that [WC], [WO] and wels nebulae are very similar to those "normal" PN: the relation between [N II] and [O III]electron temperatures, abundances of He, N, O, Ne, S and Ar, and the number of ionizing photons show no significant differences. However, some differences are observed in their infrared (IRAS) properties. wels nebulae appear bluer than [WR] PN. The central star's spectral type is clearly correlated with electron density, temperature and excitation class of the nebula, [WC] nebulae tend to be smaller than the other types. All this corroborates the view of an evolutionary sequence from cool [WC 11] central stars inside dense, low excitation nebulae towards hot [WO 1] stars with low density, high excitation nebulae. The wels PN, however, appear to be a separate class of objects, not linked to WRPN by evolution: nebular excitation, electron temperature and density, and the number of ionizing photons all cover the whole range found in the other types. Their lower mean N/O ratio and slightlylower He/H suggest progenitor stars less massive than for the other PN types. Furthermore, the differences between results of different works are dominated by the differences in observational data rather than differences in the analysis methods.

Faint recombination lines in Galactic PNe with a [WC] nucleus

“…In the case of NGC 2867, our derived O/H ratio from CELs (3.8 × 10 −4 ) is somewhat lower than previous estimates in the literature: O/H = 6.0 × 10 −4 , 4.4 × 10 −4 and 4.3 × 10 −4 by Kingsburgh & Barlow (1994), Girard et al (2007) and Peña et al (1998), respectively. Peña et al (1998) pointed out that the high O/H ratio obtained by Kingsburgh & Barlow (1994) There is a broad distribution in the O/H values reported in the literature for PB 6.…”

“…Comparing the ratio of the other elements with respect to oxygen, the agreement with these authors is excellent, except in the case of S/O, for which we have found a ratio 3 times larger than that found by Girard et al (2007). The O/H ratio derived from ORLs is much higher than solar (by almost a factor of 3).…”

“…For PB 8, we have computed O/H = 5.8 × 10 −4 from CELs, which is intermediate between the values obtained by Kingsburgh & Barlow (1994) (O/H = 4.9 × 10 −4 ) and Girard et al (2007) (O/H = 6.6 × 10 −4 ) but in relatively good agreement, taking into account the uncertainties. Comparing the ratio of the other elements with respect to oxygen, the agreement with these authors is excellent, except in the case of S/O, for which we have found a ratio 3 times larger than that found by Girard et al (2007).…”

“…We have applied the formula obtained from photoionization models of Girard et al (2007) Kwitter & Henry (2001), obtaining values of the ICF of 6.84 for PB 6−1 and 5.06 for PB 6−2.…”

Chemical abundances in Galactic planetary nebulae withSpitzerspectra

“…They also had to contain enough objects to allow us to assess their quality and internal integrity in a way that is similar to our own data presented here. These requirements were met by the following papers: de Freitas Pacheco et al (1992), Kingsburgh & Barlow (1994), Cuisinier et al (1996Cuisinier et al ( , 2000, Ratag et al (1997), Escudero & Costa (2001), Kwitter & Henry (2001), Peña et al (2001), Milingo et al (2002), Escudero et al (2004), Exter et al (2004), Górny et al (2004Górny et al ( , 2009, Girard et al (2007), Wang & Liu (2007), Cavichia et al (2010), Henry et al (2010), and Górny (2014). In short, we found useful optical spectroscopic literature data for 76, 30, and nine Galactic PNe in the lists by Stanghellini et al (2012), Perea-Calderón et al (2009), andGutenkunst et al (2008), respectively.…”