Search

The first observations of the infrared spectrum of the LMC planetary nebula SMP83 as observed by the recently launched Spitzer Space Telescope are presented. The high resolution R~600 spectrum shows strong emission lines but no significant continuum. The infrared fine structure lines are used, together with published optical spectra, to derive the electron temperature of the ionized gas for several ions. A correlation between the electron temperature with ionization potential is found. Ionic abundances for the observed infrared ions have been derived and the total neon and sulfur abundances have been determined. These abundances are compared to average LMC abundances of HII regions to better understand the chemical evolution of these elements. The nature of the progenitor star is also discussed., Comment: Accepted in ApJSup (Spitzer Special Issue), 4 pages, 2 figures

SAO 244567 (= Hen 1357) is a very young planetary nebula. It was discovered by Parthasarathy et al. (1993, A and A 267, L19). Based on the spectrum obtained around 1950 Henize (1976, ApJ Suppl 30, 491) classified it as a B or A type H-alpha emission line star. The optical spectrum of SAO 244567 obtained in 1971 shows that it was a post-AGB B1 supergiant at that time. It has turned into a planetary nebula within the last 20 years (Parthasarathy et al. 1995, A and A 300, L25).

We present the first results of a large scale infrared search for new planetary nebulae. More than 1000 unidentified sources were selected from the IRS PSC having infrared colours similar to those of known PN's. Subsequent near-infrared photometry and optical spectroscopy will be made to investigate their precise nature. We report here one to five microns photometry of 30 such sources obtained with the 1.5-m CSM telescope (Tenerife, Spain). The preliminary results indicate that many of the observed sources have near infrared colours of heavily reddened PN's (Av greater than 30 magnitudes in some cases), while a smaller fraction could represent obscured normal stars or giants surrounded by circumstellar envelopes.