===== Observations of CO+ =====

CO<sup>+</sup> is a typical PDR molecule particularly intense in the molecular cloud/HII interface region. The two strongest fine structure lines of the //N// = 2 – 1 transition as well as one fs component of the 3 – 2 transition were detected in the vicinity of the M17SW cloud by\\
W. B. Latter, C. K. Walker, and P. R. Maloney,\\
**[[https://ui.adsabs.harvard.edu/abs/1993ApJ...419L..97L|Detection of the Carbon Monoxide Ion (CO<sup>+</sup>) in the Interstellar Medium and a Planetary Nebula]]**\\
//Astrophys. J.// **419**, L97–L100 (1993).\\
The strongest 2 – 1 line was also detected toward the planetary nebula NGC 7027; this is a late type star phase after the AGB (asymptotic giant branch) phase.

The molecular cation has also been seen in the reflection nebula NGC 7023 which is in the vicinity of a Be star:\\
A. Fuente, J. Martin-Pintado,\\
**[[https://doi.org/10.1086/310532|Detection of CO<sup>+</sup> toward the Reflection Nebula NGC 7023]]**\\
//Astrophys. J.// **477**, L107–L109 (1997).

C. Ceccarelli, E. Caux, M.Wolfire, A. Rudolph, B. Nisini, P. Saraceno, and G.J. White,\\
have reported on\\
**[[https://ui.adsabs.harvard.edu/abs/1998A%26A...331L..17C|ISO Detection of CO<sup>+</sup> toward the protostar IRAS 16293–2422]]**\\
//Astron. Astrophys.// **331**, L17–L20 (1998)\\
in rather highly excited rotational states (//N// = 14 – 13 to 21 – 20). The authors attributed this to J-shocks.


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Contributor(s): H. S. P. Müller; 05, 2009


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