Observed HCN and H¹³CN lines of Y CVn with the IRAM 30 m telescope (black histograms). The red and blue curves are the synthetic lines derived from the spherically symmetric (red) and asymmetric (including maser emission; blue) envelope models. The red and green arrows point to red-shifted wings that cannot be reproduced with our spherically symmetric envelope model. The small insets in the boxes with the v = 0 J = 1− 0 and 3–2lines zoom in to show the line profiles close to the baseline (Sect. 4.2). The green profiles for these lines were calculated with the asymmetric envelopemodel without considering maser emission (Sect. 5.2.1). The H¹³ CN lines and are stronglyoverlapped and the blended line is included twice (lower right panels). The lines of the vibrational states and other with higher energies are below the detection limit. In this figure, we use two notations to name the pure rotational lines (see Appendix C.1).