One-armed Spiral Instability in a Low T/|W| Postbounce Supernova Core
  A three-dimensional, Newtonian hydrodynamic technique is used to follow the postbounce phase of a stellar core collapse event. For realistic initial data we have employed post core-bounce snapshots of the iron core of a 20 solar mass star. The models exhibit strong differential rotation but have centrally condensed density stratifications. We demonstrate for the first time that such postbounce cores are subject to a so-called low-T/|W| nonaxisymmetric instability and, in particular, can become dynamically unstable to an m=1 - dominated spiral mode at T/|W| ~ 0.08. We calculate the gravitational wave emission by the instability and find that the emitted waves may be detectable by current and future GW observatories from anywhere in the Milky Way. 
Christian D. Ott (1), Shangli Ou (2), Joel E. Tohline (2), Adam   Burrows (3) ((1) Max-Planck-Institut f. Gravitationsphysik...