Simulated light curve (upper panel) and the corresponding evolution of the average Fe charge of component 3 (lower panels). The average charge variations are shown as solid lines for gas densities of 10¹⁴, 10¹², 10¹⁰, and 10⁸ m⁻³, while the dashed curves illustrate the corresponding source light curves in the same period. As the gas density decreases, the response time to source variations becomes longer, resulting in flatter average charge variations. To highlight the response time differences across various densities, each panel presents a different total time period.