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Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in CassiopeiaA

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

Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in CassiopeiaA Thumbnail


B.W. Grefenstette

F.A. Harrison

S.E. Boggs

S.P. Reynolds

C.L. Fryer

K.K. Madsen

D.R. Wik

A. Zoglauer

C.I. Ellinger

H. An

D. Barret

F.E. Christensen

W.W. Craig

K. Forster

P. Giommi

C.J. Hailey

A. Hornstrup

V.M. Kaspi

T. Kitaguchi

J.E. Koglin

P.H. Mao

H. Miyasaka

K. Mori

M. Perri

M.J. Pivovaroff

S. Puccetti

V. Rana

D. Stern

N.J. Westergaard

W.W. Zhang


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 44Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing core and that ejected into the surrounding medium1, directly probes the explosion asymmetries. Cassiopeia A is a young2, nearby3, core-collapse4 remnant from which 44Ti emission has previously been detected5, 6, 7, 8 but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed 44Ti emission to estimated 56Ni emission9, from optical light echoes10, and from jet-like features seen in the X-ray11 and optical12 ejecta. Here we report spatial maps and spectral properties of the 44Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the 44Ti 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 instabilities in core-collapse supernovae.


Grefenstette, B., Harrison, F., Boggs, S., Reynolds, S., Fryer, C., Madsen, K., …Zhang, W. (2014). Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in CassiopeiaA. Nature, 506(7488), 339-342.

Journal Article Type Article
Publication Date Feb 20, 2014
Deposit Date Jun 25, 2014
Publicly Available Date May 21, 2015
Journal Nature
Print ISSN 0028-0836
Electronic ISSN 1476-4687
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 506
Issue 7488
Pages 339-342
Keywords High-energy astrophysics, Particle astrophysics.
Public URL


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