Journal Article

Asymmetries in core-collapse supernovae from maps of radioactive ^sup 44^Ti in Cassiopeia A

Hornstrup, A, Barret, D, Hailey, C J, Madsen, K K, Koglin, J E, Zhang, W W, Fryer, C L, Grefenstette, B W, Perri, M, Alexander, D M, Pivovaroff, M J, Mori, K, Rana, V, An, H, Kaspi, V M, Westergaard, N J, Harrison, F A, ster, K, Kitaguchi, T, Wik, D R, Christensen, F E, Boggs, S E, Reynolds, S P, Mao, P H, Stern, D, Puccetti, S, Ellinger, C I, Giommi, P, Miyasaka, H, Craig, W W, Zoglauer, A

2014

Overview

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive ^sup 44^Ti, synthesized in an exploding star near the boundary between material falling back on to the collapsing core and that ejected into the surrounding medium, directly probes the explosion asymmetries. Cassiopeia A is a young, nearby, core-collapse remnant from which ^sup 44^Ti emission has previously been detected but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed ^sup 44^Ti emission to estimated ^sup 56^Ni emission, from optical light echoes, and from jet-like features seen in the X-ray and optical ejecta. Here we report spatial maps and spectral properties of the ^sup 44^Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the ^sup 44^Ti and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead, these observations provide strong evidence for the development of low-mode convective in stabilities in core-collapse supernovae. [PUBLICATION ABSTRACT]

• Publisher: Nature Publishing Group
• Subject: Emissions / Explosions / Gamma rays / Spatial distribution / Supernovae