The IUE Spectrum of the Unusual Wolf-Rayet PG 1159--Type Star Sanduleak 3

Abstract

Archival and new lUE spectra are resented for the very hot WC 0 vi star Sand 3 (= WR 72), covering the wavelength range 1170-3200 Å. Emission-line fluxes were measured and terminal wind velocities were determined from the P Cyg N V and C iv doublets. Sand 3 is known to show some of the highest excitation stellar lines in the optical region, and the UV data confirm this by displaying lines of C IV, C V, O VI, He II, and probably O VIII and Ne VII. Nebular features include O III] λλ1661, 1667 and C III] λλ1907, 1909; [Ne V] λλ1575, 1722, 2250, 2974; [Ne IV] λλ1601, 2424; [Ar IV] λλ2854, 2869; and [Mg V] λλ1294, 1324, 2783. Based on lUE, optical, and IRAS data, a model is proposed that suggests four distinct emission zones for Sand 3: a photo spheric region, a chromosphere or corona, a nebular region, and a dust shell.

Comparisons of Sand 3 are made with the "O VI sequence" nuclei of NGC 2371-2, NGC 5189, NGC 5315, NGC 6905, and He 2-99. Although not definitely seen in Sand 3, O VII is detected for the first time in lUE spectra of the central stars of NGC 5189 and NGC 2371-2.