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Paper: Ejecta of η Car: What We are Learning about Nitrogen-Rich Chemistry
Volume: 388, Mass Loss from Stars and the Evolution of Stellar Clusters
Page: 167
Authors: Gull, T.R.
Abstract: At least one member of the binary system, η Carinae, is in late stages of CNO-cycle nuclear processing. The Homunculus, ejecta thrown out since the 1840’s, is rich in nitrogen and helium, but poor in carbon and oxygen. A very different chemistry resulted as the available oxygen was quickly used by metals with the highest condensation temperatures to form initial dust grains. Hence metals such as titanium, strontium, vanadium and scandium, under abundant in the interstellar medium, are detected in abundance in the warm, partially ionized ejecta. Although the gas densities and column densities are high, few molecules have been detected in this gas that is very different from the normal ISM and indeed from the oxygen and carbon-rich ejecta seen around massive stars in their WC and WO stages. The observations indicate that most iron-peak metals remain in the gaseous phase suggesting that the canonical gas to dust ISM ratio applied to this ejecta underestimates the total mass. In this paper we summarize published and ongoing studies leading to characterizing this unusual gas.
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