Planetary nebulae with ISO: A58 and A78 - nebulae with hydrogen-poor ejecta

Abstract

We present ISO observations of A58 and A78. Both objects are suspected to have undergone late He flashes (`born-again' nebulae). With ISOCAM we have been able to obtain data of much higher spatial resolution over the wavelength range 4.5-18 μm than has been possible in the past. In order to extract full information from our data we have developed a method to eliminate residual variations in the dark field. The results for A58 and A78 are compared with literature data and with A30 - the most prominent `born-again' planetary nebula (PN).