**Table 6:** Ionic abundances from CELs.
Ion	$\lambda$	$I(\lambda)$	N(Xⁱ⁺)/N(H⁺)
	(Å)	[ $I({\rm H}\beta)=100$ ]
C⁺	2324	177^a	$8.74\times10^{-5}$
	15.8 $\mu$ m	2.4	$5.36\times10^{-4}$
	adopted		$8.74\times10^{-5}$
C²⁺	1908	726	$3.85\times10^{-4}$
C³⁺	1550	1125	$4.18\times10^{-4}$
N⁺	5754	5.76	$1.60\times10^{-5}$
	6548	33.1	$1.53\times10^{-5}$
	6584	93.6	$1.47\times10^{-5}$
	122 $\mu$ m	0.028	$2.01\times10^{-5}$
	adopted		$1.49\times10^{-5}$
N²⁺	1750	27.1	$6.01\times10^{-5}$
	57 $\mu$ m	0.99	$4.30\times10^{-5}$
	adopted		$5.95\times10^{-5}$
N³⁺	1485	42.3	$4.85\times10^{-5}$
N⁴⁺	1240	35.9	$1.46\times10^{-5}$
O⁺	2470	25.9	$5.05\times10^{-5}$
	3726	20.8	$3.19\times10^{-5}$
	3729	7.51	$3.17\times10^{-5}$
	7320	17.9	$4.72\times10^{-5}$
	7330	14.7	$4.82\times10^{-5}$
	adopted		$4.33\times10^{-5}$
O²⁺	1663	34.5	$2.56\times10^{-4}$
	4363	25.4	$3.07\times10^{-4}$
	4931	0.254	$3.33\times10^{-4}$
	4959	564.0	$3.03\times10^{-4}$
	5007	1657.92	$3.08\times10^{-4}$
	52 $\mu$ m	6.86	$1.63\times10^{-4}$
	88 $\mu$ m	0.79	$1.83\times10^{-4}$
	adopted		$3.06\times10^{-4}$
O³⁺	1400	49.5^b	$1.39\times10^{-4}$
	26 $\mu$ m	40.2	$6.63\times10^{-5}$
	adopted		$6.63\times10^{-5}$
Ne⁺	12.8 $\mu$ m	5.33	$7.16\times10^{-6}$
Ne²⁺	3869	125.8	$5.37\times10^{-5}$
	36 $\mu$ m	2.82	$4.25\times10^{-5}$
	adopted		$5.35\times10^{-5}$
Ne³⁺	1602	13.8	$3.30\times10^{-5}$
	2422	120.4	$4.32\times10^{-5}$
	2425	41.3	$4.15\times10^{-5}$
	4714	0.903	$2.82\times10^{-5}$
	4715	0.257	$2.87\times10^{-5}$
	4724	0.807	$2.31\times10^{-5}$
	4726	0.677	$2.22\times10^{-5}$
	adopted		$4.19\times10^{-5}$
Ne⁴⁺	3346	38.0	$2.02\times10^{-5}$
	14.3 $\mu$ m	72.2	$1.23\times10^{-5}$
	adopted		$1.50\times10^{-5}$
S⁺	4068	7.61	$5.06\times10^{-7}$
	4076	2.44	$4.85\times10^{-7}$
	6716	1.72	$6.56\times10^{-7}$
	6731	3.88	$6.78\times10^{-7}$
	adopted		$5.62\times10^{-7}$
S²⁺	6312	4.23	$3.46\times10^{-6}$
	8830	0.011	$3.51\times10^{-6}$
	33.5 $\mu$ m	0.494	$2.13\times10^{-6}$
	18.7 $\mu$ m	4.69	$2.18\times10^{-6}$
	adopted		$2.75\times10^{-6}$
S³⁺	10.5 $\mu$ m	22.7	$1.56\times10^{-6}$
Cl⁺	8578	0.324	$2.08\times10^{-8}$
	9124	0.14	$3.40\times10^{-8}$
	adopted		$2.48\times10^{-8}$
Cl²⁺	3353	0.099	$4.55\times10^{-8}$
	5518	0.189	$5.40\times10^{-8}$
	8434	0.074	$7.70\times10^{-8}$
	8481	0.073	$7.81\times10^{-8}$
	adopted		$5.96\times10^{-8}$
Cl³⁺	5324	0.06	$6.07\times10^{-8}$
	7531	0.457	$5.74\times10^{-8}$
	8045	1.05	$5.69\times10^{-8}$
	11.8 $\mu$ m	0.46	$1.01\times10^{-7}$
	adopted		$6.71\times10^{-8}$
Cl⁴⁺	6.7 $\mu$ m	0.365	$1.08\times10^{-8}$
Ar⁺	7.0 $\mu$ m	1.726	$1.43\times10^{-7}$
Ar²⁺	7136	21.4	$1.09\times10^{-6}$
	7751	4.65	$9.79\times10^{-7}$
	9.0 $\mu$ m	6.26	$6.82\times10^{-7}$
	21.9 $\mu$ m	0.339	$9.20\times10^{-7}$
	adopted		$9.94\times10^{-7}$
Ar³⁺	4712	2.21	$5.84\times10^{-7}$
	4741	8.11	$6.45\times10^{-7}$
	adopted		$6.32\times10^{-7}$
Ar⁴⁺	4626	0.07	$1.63\times10^{-7}$
	6435	1.31	$1.99\times10^{-7}$
	7.9 $\mu$ m	2.50	$1.31\times10^{-7}$
	adopted		$1.54\times10^{-7}$
Ar⁵⁺	4.5 $\mu$ m	6.88	$8.58\times10^{-8}$
Mg³⁺	4.4 $\mu$ m	8.67	$3.65\times10^{-6}$
Mg⁴⁺	2783	9.53	$1.39\times10^{-5}$
	2929	3.39	$1.27\times10^{-5}$
	5.6 $\mu$ m	22.1	$9.88\times10^{-6}$
	adopted		$1.18\times10^{-5}$
Fe²⁺	4702	0.067	$3.09\times10^{-8}$
	4734	0.032	$2.97\times10^{-8}$
	4755	0.032	$3.88\times10^{-8}$
	4770	0.023	$3.07\times10^{-8}$
	4778	0.018	$3.46\times10^{-8}$
	4881	0.069^c	$1.77\times10^{-8}$
	5270	0.094	$3.70\times10^{-8}$
	adopted		$3.40\times10^{-8}$
Fe³⁺	6740	0.015	$7.08\times10^{-8}$
	7183	0.016	$3.93\times10^{-7}$
	7189	0.029	$3.73\times10^{-7}$
	adopted		$3.02\times10^{-7}$
Fe⁵⁺	5234	0.020	$1.19\times10^{-9}$
	5278	0.035	$1.24\times10^{-9}$
	5335	0.102	$1.97\times10^{-9}$
	5425	0.117	$1.56\times10^{-9}$
	5484	0.070	$2.44\times10^{-9}$
	5631	0.083	$1.35\times10^{-9}$
	adopted		$1.73\times10^{-9}$
Fe⁶⁺	4894	0.062	$1.05\times10^{-9}$
	4989	0.089	$1.68\times10^{-9}$
	5159	0.145	$1.75\times10^{-9}$
	adopted		$1.56\times10^{-9}$

^a Corrected for a $4\%$ contribution from the [O III] $\lambda$ 2322 line, assuming [O III] $I(\lambda2322)/(\lambda1663)=0.14$ .
^b Blended with the Si IV $\lambda$ 1400 line.
^c Probably underestimated because of absorption by the DIB at 4882.56 Å.

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