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Dense matter around a gamma‐ray burst ?
Author(s) -
Yoshida A.,
Namiki M.,
Otani C.,
Kawai N.,
Murakami T.,
Ueda Y.,
Shibata R.,
Uno S.
Publication year - 1999
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/1521-3994(199908)320:4/5<263::aid-asna263>3.0.co;2-w
Subject(s) - gamma ray burst , afterglow , astrophysics , physics , galaxy , line (geometry) , absorption (acoustics) , photoionization , spectral line , reflection (computer programming) , astronomy , optics , ionization , ion , programming language , geometry , mathematics , quantum mechanics , computer science
An ASCA observation of an X‐ray afterglow of a gamma‐ray burst on 28 August 1997 (GRB970828) revealed the evidence of matter near the GRB. The spectral data obtained with the observation display a large absorption column density and an emission line at ∼5 keV. The latter is possibly a red‐shifted Fe line. Hence one can derive z = 0.33 from the X‐ray data for this GRB of unknown distance. This is the first GRB with its red shift determined only by the X‐ray observation. The absorption density is estimated to be N H,src = (6.8 +4.2 —3.1 ) × 10 21 cm —2 if the absorbing material is at z = 0.33. This is remarkably high and may imply the GRB embedded in a galaxy. The line showed a time variability with a time‐scale of ∼10 4 s, from which we found that the line was formed by the dense matter in the vicinity of the GRB due to the photoionization‐recombination process or the “reflection” of an intense radiation.