Gamma-Ray bursts as probes to study interstellar dust comma and vice versa

We propose a ToO observation of a low Galactic latitude (|b| < 5 deg) and bright(15150 keV fluence >2e6 erg/cm2) GRB, with the main objective of studying thetime variable halo that might be formed by dust scattering of the GRB Xrayemission. Thin rings are formed if a large quantity of dust is concentrated indiscrete clouds along the line of sight, while diffuse dust produces atimevariable Xray halo. In the former case, very accurate measures of thedistance to the dust clouds can be derived, as well as other characteristics ofinterstellar dust. Furthermore, the GRB prompt Xray spectrum, which istypically detected only above virgul15 keV, can be reconstructed from the analysis ofthe dustscattered emission and, therefore, extended to the soft Xray band. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]