The very red afterglow of GRB 000418: Further evidence for dust extinction in a gamma-ray burst host galaxy

ISSN
0004-637X
Date Issued
2000
Author(s)
Klose, S.
Stecklum, B.
Masetti, N.
Pian, E.
Palazzi, E.
Henden, A. A.
Hartmann, D. H.
Fischer, O.
Gorosabel, J.
Sanchez-Fernandez, C.
Butler, D.
Ott, T.
Hippler, S.
Kasper, M.
Weiss, R.
Castro-Tirado, A.
Greiner, J.
Bartolini, C.
Guarnieri, A.
Piccioni, A.
Benetti, S.
Ghinassi, F.
Magazzu, A.
Hurley, K.
Cline, T.
Trombka, J.
McClanahan, T.
Starr, R.
Goldstein, J.
Mazets, E.
Golenetskii, S.
Noeske, K.
Papaderos, P.
Vreeswijk, P. M.
Tanvir, N.
Oscoz, A.
Munoz, J. A.
Ceron, JMC
DOI
10.1086/317816
Abstract
We report near-infrared and optical follow-up observations of the afterglow of the GRB 000418 starting 2.5 days after the occurrence of the burst and extending over nearly 7 weeks. GRB 000418 represents the second case for which the afterglow was initially identified by observations in the near-infrared. During the first 10 days its R-band afterglow was well characterized by a single power-law decay with a slope of 0.86. However, at later times the temporal evolution of the afterglow flattens with respect to a simple power-law decay. Attributing this to an underlying host galaxy, we find its magnitude to be R = 23.9 and an intrinsic afterglow decay slope of 1.22. The afterglow was very red with R-K approximate to 4 mag. The observations can be explained by an adiabatic, spherical fireball solution and a heavy reddening due to dust extinction in the host galaxy. This supports the picture that (long) bursts are associated with events in star-forming regions.