Spectroscopic observation of the planetary nebula IC 4846

A high-dispersion optical (3700-10100 Angstrom) spectrum was secured with t he Hamilton echelle spectrograph at the coude focus of the 120 inch (3 m) S hane telescope at Lick Observatory, with the goal of deriving chemical abun dances for the compact planetary nebula IC 4846. We also remeasured the UV spectra from the IUE archive. Diagnostics indicate that the entire planetar y nebula may be represented by an electron density N-epsilon similar or equ al to 900 cm(-3) and electron temperature T-epsilon similar or equal to 10, 500 K. However, diagnostics seem to imply that the [O II] and [S II] zone e lectron temperatures are higher than the [O III] radiating strata. The elec tron density of the [O II] and [S II] zone might be higher as well (for whi ch N-epsilon similar or equal to 20,000 cm(-3)). The photoionization model, which represents most of the observed line intensities, seems to confirm t his physical condition, although the actual situation may be much more comp licated. On the basis of the semiempirical ionization correction method and the photoionization model calculation, we derived the chemical abundances in this planetary nebula. Our optical data were compared with the image-tub e scanner data from Aller & Czyzak. Apparently, there is a longterm spectra l line variation in IC 4846. Chemical abundances derived in the present stu dy agree, within 30%, with those previously estimated in Aller & Czyzak, ex cept for carbon; the C, N, O, and Ne ratios are lower than both the average planetary nebula and the solar abundance. IC 4846 is a metal-deficient pla netary nebula that may have evolved from a Population II progenitor.