The Reionization of Unshocked Ejecta in SN1006

Abstract

AbstractThe fortuitous positioning of the Schweizer and Middleditch OB subdwarf behind SN1006 has permitted the detection and subsequent confirmation by IUE of broad (±5000 km/s) Fe II absorption features which probably arise from unshocked iron ejecta in the center of SN1006. The mass of detected Fe II, ∽0.012 M⊙, is however only 1/25 of the ∽0.3 M⊙ of Fe within ±5000 km/s predicted by carbon deflagration models. IR and optical observations exclude any appreciable iron in grains or Fe I, but high ion stages, Fe III and up, oould be present. Promising mechanisms for ionizing the unshocked iron in SN1006 include the radioactive decay of 44Ti, and photoionization by UV and X-ray emission from the reverse shock. Although the photoionization model works, insofar as it permits as much as 0.2 M⊙ of unshocked iron in the center of SN1006, agreement with the IUE data requires that the ejecta density profile be flatter, less centrally concentrated, than the W7 deflagration model of Nomoto, Thielemann, and Yokoi.