X-ray Lines in Afterglows of GRBs:  The Nickel-and-Dime Model

by

Ralph A.M.J. Wijers
19 July 2001

A number of GRB afterglows have shown the presence of an X-ray line around 7 keV (in the restframe of the burst) in the first days after the burst. This has been identified with iron, of which large amounts are needed for these very strong lines. This has been taken as evidence for a supernova-like origin of GRBs, with the recent stellar explosion providing the iron needed.

A problem with this idea is that supernovae make Nickel, which normally turns into Iron on an 80-day time scale, and so we would expect to see a Nickel line at 8 keV in stead. I will discuss our recent attempts to solve this problem in the context of hypernova models. I will also discuss some interesting peculiarities of the final fate of the Nickel. As an introduction to this latter issue, the interested reader of this abstract may ask himself/herself this question:

Is ⁵⁶Ni²⁸⁺ radioactive or not? If so, what is its half-life?

It is, of course, a trick question, and may even be unfair.

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