Issue |
Astron. Astrophys. Suppl. Ser.
Volume 138, Number 3, September 1999
Gamma-Ray Bursts in the Afterglow Era Contents Rome, November 3-6, 1998
|
|
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Page(s) | 479 - 480 | |
DOI | https://doi.org/10.1051/aas:1999318 | |
Published online | 15 September 1999 |
GRB 970228 and GRB 980329 and the nature of their host galaxies
Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, U.S.A.
Received:
21
January
1999
Accepted:
30
June
1999
We find that the local galactic extinction towards the field of
gamma-ray burst GRB 970228 is , which implies
a substantial dimming and change in the spectral slope of the intrinsic
GRB 970228 afterglow. We measure a color
for the extended source coincident with the
afterglow. Taking into account our measurement of the extinction
toward this field, this color implies that the extended source is most
likely a galaxy undergoing star formation, in agreement with our
earlier conclusion (Castander & Lamb 1998). In a separate analysis, we
find that the inferred intrinsic spectrum of the GRB 980329 afterglow is
consistent with the predictions of the simplest relativistic fireball
model. We also find that the intrinsic spectrum of the afterglow is
extincted both by dust (source frame
1 mag), and that the
shape of the extinction curve is typical of young star-forming regions
like the Orion Nebula but is not typical of older star-forming or
starburst regions. The ≈ 2 mag drop between the R and the
I bands can be explained by the far-ultraviolet non-linear component
of the extinction curve if
, and by the 2175 Å bump
if
; other redshifts are not consistent with the
observational data, given our general model.
Key words: gamma-rays: bursts
© European Southern Observatory (ESO), 1999