Chemical Abundances of the Planetary Nebula IC 4634 and Its Central Star

Abstract

We have measured the spectral line intensities of the metal-poor planetary nebula IC 4634. Using a photoionization model calculation, we try to fit the optical and UV region spectra, i.e., Hamilton echelle and IUE observations. From direct images, one expects complicated density variations, but the model predicts a range in densities that may be smaller than actually exist. We find N_ɛ~5000 cm^-3. In spite of the geometrical complexity of the S-shaped double-lobed structure, the simple photoionization model with a spherical symmetry can fit most emission lines fairly well. The derived chemical composition has been compared with previous estimates and also with the Sun. The metallicity in IC 4634 appears to be lower than in the Sun or the average planetary nebula. The most likely temperature of the central ionizing source of IC 4634 appears to be ~55,000 K. We find a central star mass of ~0.55 M_solar from comparison with theoretical evolutionary tracks.