Observation of X-ray lines from a gamma-ray burst (GRB991216): evidence of moving ejecta from the progenitor.
We report on the discovery of two emission features observed in the x-ray spectrum of the afterglow of the gamma-ray burst (GRB) of 16 December 1999 by the Chandra X-ray Observatory. These features are identified with the Ly(alpha) line and the narrow recombination continuum by hydrogenic ions of iron at a redshift z = 1.00 +/- 0.02, providing an unambiguous measurement of the distance of a GRB. Line width and intensity imply that the progenitor of the GRB was a massive star system that ejected, before the GRB event, a quantity of iron approximately 0.01 of the mass of the sun at a velocity approximately 0.1 of the speed of light, probably by a supernova explosion.
Piro
L
L
Istituto Astrofisica Spaziale, Consiglio Nazionale delle Ricerche (CNR), Via Fosso del Cavaliere, 00133 Roma, Italy. piro@ias.rm.cnr.it
Garmire
G
G
Garcia
M
M
Stratta
G
G
Costa
E
E
Feroci
M
M
Mészáros
P
P
Vietri
M
M
Bradt
H
H
Frail
D
D
Frontera
F
F
Halpern
J
J
Heise
J
J
Hurley
K
K
Kawai
N
N
Kippen
R M
RM
Marshall
F
F
Murakami
T
T
Sokolov
V V
VV
Takeshima
T
T
Yoshida
A
A