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Non-Equilibrium Ionization States of GRB Environments

D. Yonetoku·T. Murakami·K. Masai·A. Yoshida·N. Kawai·M. Namiki
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Abstract

Iron spectral features are thought to be the best tracer of a progenitor of gamma-ray bursts (GRBs). The detections of spectral features such as an iron line and/or a Radiative Recombination edge and Continuum (RRC) were reported in four X-ray afterglows of GRBs. However their properties were different each other burst by burst. For example, Chandra observation of GRB 991216 reported both the strong H-like iron line together with its RRC. On the contrary, Yoshida et al. (2001) report only a detection of the strong RRC in GRB 970828 with ASCA. Since it is difficult to produce the strong RRC, we have to consider special condition for the line and/or the RRC forming region. In this paper, we point out a possibility of a ``non-equilibrium ionization state'' for the line and the RRC forming region.

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D. Yonetoku, T. Murakami, K. Masai, A. Yoshida, N. Kawai, M. Namiki. 2001-07-18. Non-Equilibrium Ionization States of GRB Environments. https://doi.org/10.1086/323142

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