Upper panel: radial profile of excitation temperature for H¹³CN(1−0), red solid line, and HN¹³C(1−0), blue dashed line, in L1498 as predicted by our best fit Monte Carlo model; the vertical dashed line represents the central hole radius and the horizontal dashed line shows the cosmic background temperature limit. Lower panel: comparison between HN¹³C(1−0) and H¹³CN(1−0) local values of the excitation temperature in each core shell; the dashed line depicts the positions where the two excitation temperatures would be equal.