Recovery from a giant eruption: the case of eta Car

Kris Davidson

University of Minnesota, USA

Giant eruptions or SN Impostors are far more mysterious than "real" supernovae, because they are scarcer and because they have received far less theoretical effort. One rather special problem is the disequilibrium state of a post-eruption star. This may be partially observable by watching the star's gradual recovery; which, in principle, may offer clues to the basic instability mechanisms. So far, the only example that can be observed well enough is eta Carinae. Its history offers tantalizing clues and counter-clues. For instance: (1) Before 2000, the recovery timescale seemed to be of order 150 years; but (2) around 2000, many parameters began to change much more rapidly; and (3) the 150-year recovery process so far has been punctuated by about three abrupt changes of state. This strange combination of facts has received almost no theoretical attention so far.

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