Examining the evidence for dust destruction in GRB 980703

Abstract

Aims. The effects that gamma-ray bursts have on their environments is an important and outstanding issue. Dust destruction in particular has long been predicted while observational evidence is difficult to obtain. We examine the evidence for dust destruction by GRB 980703, in which various inconsistent measurements of the host galaxy extinction have been made using the GRB afterglow emission. Methods. We construct a spectral energy distribution from nIR to X-ray to measure the extinction at early times and compare this with previous findings. We also construct nIR/optical SEDs at intermediate epochs to examine a previously reported decrease in extinction. Results. The extinction is very high for a GRB host galaxy. The earliest extinction measurement is likely to be lower than previously estimated, and consistent with most later measurements. In a series of SEDs we do not find any evidence of variable extinction. We therefore conclude that there is no clear evidence of dust destruction in this case.