Passage: Unexpectedly, three H+3 lines were detected in 1998 by McCall et al. in the diffuse cloud sightline of Cyg OB2 No. 12. Before 1998, the density of H2 was thought to be too low to produce a detectable amount of H+3. McCall detected a temperature of ~27 K (−246 °C) and a column density of ~1014/cm2, the same column density as Geballe & Oka. Since then, H+3 has been detected in many other diffuse cloud sightlines, such as GCS 3-2, GC IRS 3, and ζ Persei.

Question: What is the temperature that McCall detected?
~27 K (−246 °C)