Dependence of the transit profile on the input parameters of the coma model listed in Table 2. In all cases, the comet passes through the center of the star’s disk (impact parameter b = 0). Panel a: transit of comet 1P/Halley (the index of the differential particle size distribution (n) changes, other parameters are fixed at: T =1 month; a_min = 0.1 µm and a_max = 20.0 µm; υ_d = 1.0 km s⁻¹; υ_tang = 67.0 km s⁻¹.) Panel b: transit of comet C/1995 O1 (the time of tail formation T changes, other parameters are fixed at: a_min = 0.1 µm and a_max = 20.0 µm; n = 3.5; υ_d = 1.0 km s⁻¹; υ_tang = 51.0 km s⁻¹.) Panel c: transit of comet C/1995 O1 (the particle terminal velocity υ_d changes, other parameters are fixed at: T = 4 yr; a_min = 5.0 µm and a_max = 999.0 µm; n = 3.5; υ_tang = 22.7 km s⁻¹). Panel d: transit of comet C/1995 O1 (the tangential velocity changes, other parameters are fixed at: T = 2 months; a_min = 0.1 µm and a_max = 20.0 µm; n = 2; υ_d = 3.0 km s⁻¹).