**Table 7:** Ionic abundances from ORLs.
Ion	$\lambda$	$I(\lambda)$	N(Xⁱ⁺)/N(H⁺)
	(Å)	[ $I({\rm H}\beta)=100$ ]
He⁺	4471	3.222	$5.63\times10^{-2}$
	6678	2.538	$5.82\times10^{-2}$
	5876	10.87	$5.80\times10^{-2}$
	adopted		$5.80\times10^{-2}$
He²⁺	4686	47.75	$4.04\times10^{-2}$
	4860	2.833	$4.39\times10^{-2}$
	adopted		$4.10\times10^{-2}$
C²⁺	3918	0.024	$1.04\times10^{-3}$
	4267	0.575	$6.40\times10^{-4}$
	4802	0.032	$1.01\times10^{-3}$
	5342	0.034	$7.15\times10^{-4}$
	6462	0.060	$6.64\times10^{-4}$
	6578	0.231	$3.99\times10^{-4}$
	7231	0.108	$2.56\times10^{-4}$
	adopted		$5.54\times10^{-4}$
C³⁺	4070	0.425	$2.70\times10^{-4}$
	4187	0.197	$2.70\times10^{-4}$
	8196	0.289	$6.20\times10^{-4}$
	adopted		$3.87\times10^{-4}$
C⁴⁺	4658	0.579^a	$2.81\times10^{-4}$
N²⁺	3995	0.009	$8.49\times10^{-5}$
	4041	0.012	$8.42\times10^{-5}$
	4043	0.008	$7.41\times10^{-5}$
	4678	0.007	$1.18\times10^{-4}$
	4179	0.005	$7.62\times10^{-5}$
	4237	0.005	$5.07\times10^{-5}$
	4431	0.006	$9.75\times10^{-5}$
	4631	0.021	$8.86\times10^{-5}$
	5667	0.014	$6.03\times10^{-5}$
	5680	0.033	$7.60\times10^{-5}$
	5686	0.019	$2.47\times10^{-4}$
	5927	0.002	$6.83\times10^{-5}$
	5940	0.004	$1.37\times10^{-4}$
	6482	0.004	$9.90\times10^{-5}$
	adopted		$1.03\times10^{-4}$
N³⁺	4379	0.059^b	$2.56\times10^{-5}$
N⁴⁺	3483	0.031	$1.22\times10^{-5}$
	4707	0.015	$2.34\times10^{-5}$
	7582	0.011	$2.29\times10^{-5}$
	7703	0.021	$1.66\times10^{-5}$
	adopted		$1.68\times10^{-5}$
N⁵⁺	4945	0.043	$7.02\times10^{-6}$
O²⁺	4072	0.134	$5.55\times10^{-4}$
	4111	0.012	$5.04\times10^{-4}$
	4119	0.035	$3.99\times10^{-4}$
	4133	0.013	$2.40\times10^{-4}$
	4153	0.021	$2.72\times10^{-4}$
	4317	0.022	$2.80\times10^{-4}$
	4320	0.026	$3.06\times10^{-4}$
	4346	0.017	$2.17\times10^{-4}$
	4349	0.041	$2.08\times10^{-4}$
	4367	0.035	$4.41\times10^{-4}$
	4639	0.070	$6.38\times10^{-4}$
	4649	0.165	$3.13\times10^{-4}$
	4662	0.036	$2.56\times10^{-4}$
	4676	0.037	$3.14\times10^{-4}$
	adopted		$3.95\times10^{-4}$
O³⁺	4435	0.019	$4.04\times10^{-5}$
	5592^c	0.105	$6.20\times10^{-5}$
	adopted		$4.04\times10^{-5}$
O⁴⁺	3410	0.103	$1.43\times10^{-5}$
	4632	0.188	$1.19\times10^{-5}$
	adopted		$1.27\times10^{-5}$
O⁵⁺	7611	0.014	$7.46\times10^{-6}$
Ne²⁺	3327	0.016	$8.86\times10^{-5}$
	3335	0.042	$6.24\times10^{-5}$
	3355	0.027	$7.68\times10^{-5}$
	3694	0.023	$6.78\times10^{-5}$
	3777	0.011	$8.35\times10^{-5}$
	4392	0.011	$8.43\times10^{-5}$
	4409	0.017	$1.96\times10^{-4}$
	adopted		$8.63\times10^{-5}$
Mg²⁺	4481	0.023	$2.43\times10^{-5}$

^a Corrected for a $23\%$ contribution from the [Fe III] $\lambda$ 4658 line, assuming [Fe III] $I(\lambda4658)/I(\lambda4734)=5.33$ .
^b Corrected for a total of $11\%$ contribution from the C III and Ne II $\lambda$ 4380 lines, assuming C III $I(\lambda4380)/(\lambda4383)=3.5$ and Ne II $I(\lambda4380)/(\lambda4392)=0.61$ .
^c Also excited partly by charge exchange with H⁰ (Liu et al. 1993).

Source LaTeX | All tables | In the text

	1 Introduction
	2 Observations
	3 Raman scattering features
	4 Reddening summary
	5 Physical conditions
	6 Elemental abundances
	7 The central star
	8 Summary
	References
	Online Material
	Appendix A: Emission from heavy elements (Z>30)
	Appendix B: Atomic data references