Hanning-smoothed spectrum taken from the compact-configuration dataset toward zone A (offset position: − 0.42″, − 0.43″). The black lines are the observed data, while the red lines are the model spectrum of CO⁺N = 3–2, F = 3/2–1/2 (353.0589 GHz), 5/2–3/2 (353.7413 GMHz) and 7/2–5/2 (354.0142 GHz) under LTE assumption. The LTE intensity ratio of the hyperfine transitions is ~1:14:20 (increasing in frequency). The F = 7/2–5/2 transition at 354.0142 GHz is not detected in our SMA data.