Issue |
A&A
Volume 401, Number 2, April II 2003
|
|
---|---|---|
Page(s) | 593 - 597 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20030094 | |
Published online | 21 March 2003 |
Possible geometries of afterglow generation in the gamma-ray burst GRB 990705
Department of Astronomy, Nanjing University, Nanjing 210093, PR China e-mail: daizigao@public1.ptt.js.cn;tlu@nju.edu.cn
Corresponding author: X. Y. Wang, xywang@nju.edu.cn
Received:
23
July
2002
Accepted:
9
January
2003
The absorption feature detected in the prompt X-ray
emission of GRB 990705 has important consequences for its
circum-burst environment and therefore on its afterglow. Here we
investigate whether the circum-burst environment constrained by
the absorption feature could be consistent with the observed
H-band afterglow, which exhibits an earlier power law decay
() but a much faster decay (
;
) about one day after the burst. Two
possible geometries of the afterglow-emitting regions are
suggested: 1) afterglow emission produced by the impact of the
fireball on the surrounding torus, which serves as the absorbing
material of the X-ray feature, as would be expected in the models
involving that a supernova explosion precedes the gamma-ray burst
by some time; 2) afterglow emission produced in the dense
circum-burst medium inside the torus. In case 1), the faster decay
at the later time is attributed to the disappearance of the shock
due to the counter-pressure in the hot torus illuminated by the
burst and afterglow photons. For case 2), the circum-burst medium
density is found to be very high (
) if the emitting plasma is a jet or even higher if it is
spherical. Future better observations of afterglows of GRBs that
have absorption features might make it possible to make a more
definite choice between these two scenarios.
Key words: gamma rays: bursts / line: formation / radiation mechanism: nonthermal
© ESO, 2003
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.