Astron. Astrophys. Suppl. Ser. 138, 453-454

Broad-band spectral evolution of GRB afterglows

N. Masetti¹ - E. Pian¹ - E. Palazzi¹ - L. Amati¹ - T.J. Galama² - L. Nicastro³ - P.M. Vreeswijk² - F. Frontera¹ - J. van Paradijs²

Send offprint request: masetti@tesre.bo.cnr.it

1 - Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy
2 - Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
3 - I.F.C.A.I., CNR, via Ugo La Malfa 153, I-90146 Palermo, Italy

Received December 29, 1998; accepted April 21, 1999

Abstract:

Quasi-simultaneous Spectral Energy Distributions (SEDs) at different epochs of four among the most intensively observed Gamma-Ray Burst (GRB) afterglows have been constructed in order to investigate and compare the temporal evolution of their multiwavelength emission. The data suggest that generally the peak frequency moves toward lower frequencies with time. SED local maxima in the optical/IR range are present in some cases, possibly due to dust absorption within the host galaxy.

Key words: methods: data analysis -- gamma-rays: bursts