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Discovery of a Transient Absorption Edge in the X-ray Spectrum of GRB 990705
Lorenzo Amati,1*Filippo Frontera,12Mario Vietri,3Jean J. M. in
't Zand,4Paolo Soffitta,5Enrico Costa,5Stefano Del Sordo,6Elena Pian,1Luigi Piro,5Lucio A. Antonelli,7D. Dal Fiume,1Marco Feroci,5Giangiacomo Gandolfi,5Cristiano Guidorzi,2John Heise,4Erik Kuulkers,4Nicola Masetti,1Enrico Montanari,2Luciano Nicastro,6Mauro Orlandini,1Eliana Palazzi1
We report the discovery of a transient equivalent hydrogen column
density with an absorption edge at ~3.8 kiloelectron voltsin the
spectrum of the prompt x-ray emission of gamma-ray burst(GRB) 990705. This feature can be satisfactorily modeled witha photoelectric
absorption by a medium located at a redshift of~0.86 and with an
iron abundance of ~75 times the solar one. Thetransient behavior is
attributed to the strong ionization producedin the circumburst medium
by the GRB photons. The high iron abundancepoints to the existence of
a burst environment enriched by a supernovaalong the line of sight.
The supernova explosion is estimatedto have occurred about 10 years
before the burst. Our resultsagree with models in which GRBs originate
from the collapse ofvery massive stars and are preceded by a supernova
event.
1 Istituto di Tecnologie e Studio delle
Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy.
2 Dipartimento Fisica, Università di Ferrara,
Via Paradiso 12, 44100 Ferrara, Italy.
3 Dipartimento Fisica, Terza Università di
Roma, Via della Vasca Navale 84, 00146 Roma, Italy.
4 Space Research Organization Netherlands,
Sorbonnelaan 2, 3584 CA Utrecht, Netherlands.
5 Istituto di Astrofisica Spaziale, CNR, Via Fosso
del Cavaliere, 00133 Roma, Italy.
6 Istituto di
Fisica Cosmica con Applicazioni all' Informatica, Via U. La Malfa,
153, 90146 Palermo, Italy.
7 Osservatorio
Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone (RM),
Roma, Italy.
*
To whom correspondence should be addressed E-mail:
amati{at}tesre.bo.cnr.it
The editors suggest the following Related Resources on Science sites:
In Science Magazine
NEWS FOCUS
Govert Schilling (3 November 2000) Science290 (5493), 926.
[DOI: 10.1126/science.290.5493.926] |Summary »|Full Text »
NEWS FOCUS
Govert Schilling (3 November 2000) Science290 (5493), 927.
[DOI: 10.1126/science.290.5493.927] |Summary »|Full Text »
REPORTS
L. Piro, G. Garmire, M. Garcia, G. Stratta, E. Costa, M. Feroci, P. Mészáros, M. Vietri, H. Bradt, D. Frail, F. Frontera, J. Halpern, J. Heise, K. Hurley, N. Kawai, R. M. Kippen, F. Marshall, T. Murakami, V. V. Sokolov, T. Takeshima, and A. Yoshida (3 November 2000) Science290 (5493), 955.
[DOI: 10.1126/science.290.5493.955] |Abstract »|Full Text »|PDF »
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Gamma-Ray Bursts: Accumulating Afterglow Implications, Progenitor Clues, and Prospects.
Observation of X-ray Lines from a Gamma-Ray Burst (GRB991216): Evidence of Moving Ejecta from the Progenitor.
L. Piro, G. Garmire, M. Garcia, G. Stratta, E. Costa, M. Feroci, P. Mészáros, M. Vietri, H. Bradt, D. Frail, et al. (2000)
Science
290, 955-958
|Abstract »|Full Text »
