Infrared search for ejecta-type Wolf-Rayet star ring nebulae

摘要

Our examination of both the two dozen Wolf-Rayet (WR) stars with known optical ring nebula and the remaining 140 or so known galactic WR stars was completed. All four bands in the IRAS Sky-Flux Imaging Data set were used. Using magnetic tapes containing copies of the IRAS Sky-Flux images available at the University of Colorado, the precise locations of all known galactic WR stars were examined both in the 4 individual wavelength bands (12, 25, 60, and 100 microns) as well as examining the temperature sensitive 25/60 and 60/100 micron ratio images. The results of this survey was the detection of over 40 WR stars, the majority of which are of the carbon-rich or 'WC' type. This means that via the IRAS image data, one can detect, quite easily in most cases, most of the brighter WC stars in the galactic plane because of their carbon-rich surrounding mass-loss shells. However, the more interesting cases were the remaining detected WR stars all of which were late WN stars. Two WN WR stars, HD 142414 and HD 86161, which appear probably to have associated ring nebulae based on their observed IRAS fluxes were detected. These stars may be strong IR emitters due to the presence of large mass loss shells around them, like the WC stars even though they are not known to universally have massive circumstellar shells. The total number of WN(L) cases detected numbered about 10, five of which had already been previously detected using IRAS by other studies. The new five stars represent new IR detections and may indicate that WN(L) commonly have IR emission shells. A paper detailing these IR detection using the IRAS image data set is currently in final preparation for submission to the Astronomical Journal. In the course of this project, a remarkably large, old, and yet IR bright supernova remnant (SNR) was identified and found to be associated with the WNL WR star HD 192163. This 1.5 x 2 deg sized remnant, which is seen only in the infrared and not in any published radio map, lies nearly centered on and completely surrounds the WR star.