2013ApJ...774...56M

Pety et al. recently reported the detection of several transitions of an unknown carrier in the Horsehead PDR and attribute them to l-C₃H⁺. Here, we have tested the predictive power of their fit by searching for, and identifying, the previously unobserved J = 1-0 and J = 2-1 transitions of the unknown carrier (B11244) toward Sgr B2(N) in data from the publicly available PRIMOS project. Also presented here are observations of the J = 6-5 and J = 7-6 transitions toward Sgr B2(N) and Sgr B2(OH) using the Barry E. Turner Legacy Survey and results from the Kaifu et al. survey of TMC-1. We calculate an excitation temperature and column density of B11244 of ∼10 K and ∼10¹³/cm2 in Sgr B2(N) and ∼79 K with an upper limit of ≤ 1.5 x10¹³/cm2 in Sgr B2(OH) and find trace evidence for the cation's presence in TMC-1. Finally, we present spectra of the neutral species in both Sgr B2(N) and TMC-1, and comment on the robustness of the assignment of the detected signals to l-C₃H⁺.