Three high-excitation planetary nebulae in the Magellanic Clouds were successfully observed with the International Ultraviolet Explorer. Emission lines as well as nebular and stellar continua were detected. Fluxes in the lines 1550 C IV, 1640 He II, 1663 O III, and 1909 C III were measured in spectra of LMC P40, SMC N2, and SMC N5 obtained with the IUE short wavelength spectrograph; 2422 Ne IV was measured in P40 with the long wavelength spectrograph. The data were analyzed together with groundbased observations by Aller in order to derive ionization models and the nebular abundances of He, C, N, O, S, Ar. The C abundances are as large as those typically found in galactic planetaries, although the interstellar media of the Clouds are notably deficient in C. Thus, the C was synthesized in the progenitor stars and presumably was lifted to the stellar envelopes by convection prior to the ejection of the nebulae. Other planetary nebulae in the Clouds, as well as the planetary nebula in the Fornax galaxy, may be observable with IUE.

The discovery of a new planetary nebula from (O III) interference filter imagery is reported. The nebula, PN 136 + 5°1, is 15′ in diameter and asymmetric in appearance. Spectrophotometry of the central regions indicate it is of excitation class between 8 and 10. A single bright condensation within the nebula exhibits emission lines of much lower ionization with (S II) λλ 6717, 6731 line intensities indicating an electron density of about 350 ± 150 cm−3. Seeing limited (O III) imagery of this planetary nebula is also presented. (This article is appearing in Astron. Astrophys. in the near future).

Radiation scattered by a stellar wind back into the photosphere alters the temperature-depth relation and thus the stellar flux distribution. The fraction of the radiation returned to the star at every wavelength has been calculated using stellar wind models accounting for approximately 10 000 lines. Model stellar atmospheres containing hydrogen and helium, both with and without the assumption of LTE, have been computed allowing for the reflected radiation. For realistic wind and stellar parameters relevant to central stars of planetary nebulae, we obtain a 25% increase in the surface temperature and in the optical brightness temperature, and a 2 order-of-magnitude increase in the flux in the He II continuum.

The bright nebula S274 (YM29), 8′ across has been classified as a planetary by Abell (1966) although it has been considered a SNR by other authors. We have determined radial velocities at 173 points on this nebula from four Fabry-Pérot interferograms. The velocity field exhibits a great deal of structure. The average expansion velocity is + 31.5 ± 8 km s−1. The mean radial velocity of S274 is not well determined due to the nature of the velocity field, while the overall velocity (173 points) is + 33 ± 21 km s−1. Points at the outer boundary yield an average of 22 ± 14 km s−1 while the average of the double points is 25 km s−1. The age of expansion of the nebula is estimated at 6.8 × 103yr. The physical parameters of this object are consistent with those of a planetary nebula.

Three stellar-like objects, previously identified as planetary nebulae, were observed with the Image Intensifier-SIT multichannel spectrograph at the 2.1 m telescope in San Pedro Mártir. The mis-identified planetaries are B1 3-11, He 2-417 and He 2-468. All of them show strong permitted H and He lines, detectable stellar continuum with absorption late-type bands and several other emission lines, including the unidentified λ 6830 Å feature. Clearly, the three objects are symbiotic stars, and not planetary nebulae. We present low-dispersion spectra for the three objects in the 3800-7000 Å spectral range.