Column density ratios of HCN over HC¹⁵N at 1 Myr as a function of radius for a range of model parameters: disk mass (M_disk), flaring angle power law (ψ), large grain fraction (f_L) and stellar spectrum. The dashed gray line marks the elemental ¹⁴N/¹⁵N ratio of 440. The dark and light gray shaded regions indicate the range of observed HCN/HC¹⁵N ratios and uncertainties from Guzmán et al. (2017), probing material out to 100 au. The abbreviation “TT:10⁻⁸” means a T Tauri stellar spectrum with a UV excess for an accretion rate of 10⁻⁸ M_⊙ yr⁻¹.