The preferred description of the time dependence of Fe Kα declining luminosity of the B2 cloud. (i) Short-dashed (red) line: the best fit for constant density model of the cloud; (ii) long-dashed (blue) line: two-component constant density model of the core and envelope; (iii) thick continuous (green) line: dense core with a radially decreasing density of the envelope. This final model gives the most precise representation of the data and also seems to describe the most realistic situation.