Illustration of the temperature and column density ranges that, for fixed parameters R_i ≈ 0.25 AU, q = −1.5, i = 40°, and υ_G = 1 km s⁻¹, lead to CO first overtone bandhead maximum flux values between 2 and 25% continuum, which represent the minimum detectable and the maximum observed normalized fluxes respectively. Left: the accessible parameter space for different values of the temperature exponent p (models are for B268). Right: the same, for the different stars as varying in mass and continuum emission (models are for p = −2).