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We report deep long-slit emission-line spectra, the line flux ratios, andDoppler profile shapes of various bright optical lines. The low-ionizationlines (primarily [N I], [O I], [S II], and [N II]) originate in shocked knots,as reported by many previous observers. Dust-scattered lines of higherionization are seen throughout the lobes but do not peak in the knots. Ouranalysis of these line profiles and the readily discernible stellar continuumshows that (1) the central star is an active symbiotic (whose spectrumresembles the central stars of highly bipolar and young PNe such as M2-9 andHen2-437) whose compact companion shows a WC8-type spectrum, (2) extendednebular lines of [O III] and He I originate in the heavily obscured nuclear HII region, and (3) the Balmer lines observed throughout the lobes are dominatedby reflected H{\alpha} emission from the symbiotic star. Comparing our lineratios with those observed historically shows that (1) the [O III]/H\b{eta} andHe I/H\b{eta} ratios have been steadily rising by large amounts throughout thenebula, (2) the H{\alpha}/H\b{eta} ratio is steadily decreasing whileH{\gamma}/H\b{eta} remains nearly constant, and (3) the low-ionization lineratios formed in the shocked knots have been in decline in different ways atvarious locations. We show that the first two of these results might beexpected if the symbiotic central star has been active and if its brightH{\alpha} line has faded significantly in the past 20 years.

The Emerging Planetary Nebula CRL 618 and its Unsettled Central Star(s)