Strongly Variable z=1.48 FeII and MgII Absorption in the Spectra of z=4.05 GRB 060206

摘要: We report on the discovery of strongly variable FeII and MgII absorption lines seen at z=1.48 in spectra z=4.05 GRB 060206 obtained between 4.13 to 7.63 hours (observer frame) after burst. In particular, line equivalent width (EW) decayed rapidly from 1.72+-0.25 AA 0.28+-0.21 AA, only increase 0.96+-0.21 a later date spectrum. The doublet shows even more complicated evolution: weaker drops 2.05+-0.25 0.92+-0.32 but then than doubles 2.47+-0.41 data. ratio EWs for is also variable, being closer 1:1 (saturated regime) when are stronger becoming 2:1 (unsaturated weaker, consistent with expectations based atomic physics. have investigated rejected possibility any instrumental or atmospheric effects causing observed strong variations. Our clearly intervening lends very support their scenario, which characteristic size patches ``clouds'' comparable beam size, i.e, about 10^16 cm. discuss various implications this discovery, including nature absorbers, physics GRBs, measurements chemical abundances quasar lines.