2120 20160701171659.0 10.1093/mnras/stu2173 DOI ASTROimport-277 Chatzikos, M. 2015 Implications of coronal line emission in NGC 4696* We announce a new facility in the spectral code CLOUDY that enables tracking the evolution of a cooling parcel of gas with time. For gas cooling from temperatures relevant to galaxy clusters, earlier calculations estimated the [Fe XIV] λ5303/[Fe X] λ6375 luminosity ratio, a critical diagnostic of a cooling plasma, to slightly less than unity. By contrast, our calculations predict a ratio of ˜3. We revisit recent optical coronal line observations along the X-ray cool arc around NGC 4696 by Canning et al., which detected [Fe X] λ6375, but not [Fe XIV] λ5303. We show that these observations are not consistent with predictions of cooling flow models. Differential extinction could in principle account for the observations, but it requires extinction levels (AV > 3.625) incompatible with previous observations. The non-detection of [Fe XIV] implies a temperature ceiling of 2.1 million K. Assuming cylindrical geometry and transonic turbulent pressure support, we estimate the gas mass at ˜1 million M⊙. The coronal gas is cooling isochorically. We propose that the coronal gas has not condensed out of the intracluster medium, but instead is the conductive or mixing interface between the X-ray plume and the optical filaments. We present a number of emission lines that may be pursued to test this hypothesis and constrain the amount of intermediate-temperature gas in the system. Williams, R. J. R. Ferland, G. J. Canning, R. E. A. Fabian, A. C. Sanders, J. S. van Hoof, P. A. M. Johnstone, R. M. Lykins, M. Porter, R. L. Monthly Notices of the Royal Astronomical Society 446 2 2015 1234-1244 http://esoads.eso.org/abs/2015MNRAS.446.1234C published in REFERD