HCN production rates as a function of heliocentric distance for comet C/2013 R1 Lovejoy. Error bars shown for the current data (crosses) do not include uncertainties in model parameters, but only reflect measurement errors. Circles represent data from Paganini et al. (2014), stars data from Agúndez et al. (2014), and triangles data from Biver et al. (2014). The solid line illustrates the best fit to the current data, s^-1, while the dashed line represents , the dash-dotted line , and the dotted line ; see text for details.