Critical Evaluation: Phenanthrene with Cyclohexane (IUPAC SDS Volume 59)
Phenanthrene solubilities in cyclohexane were retrieved from papers by McLaughlin and Zainal (1), Gordon and Scott (2) and Choi (3). All three studies report values at several temperatures. There is not a prior reason to exclude any of the three studies from the critical evaluation.
Regressional analysis of the experimental data as Ln x1 versus 1/T yielded the following mathematical relationship: Ln x1 = - 5215.6 (1/T) + 14.1709 (r=0.9897) for variation of naphthalene solubility with absolute temperature (see graph below). Phenanthrene does exhibit a solid-solid lambda point phase transition from around 331 to 361 K (4). A graphical plot of Ln x1 versus 1/T is linear if the enthalpy of the transition is relatively small compared to the solute's enthalpy of fusion, as is the case here. The slight nonlinear behavior is undoubtedly attributed to the addittional phase transition.
Figure
Solubility graph
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References:

1 McLaughlin, E.; Zainal, H. A.; J. Chem. Soc. 1960, 3854-3857.
2 Gordon, L. J.; Scott, R. L.; J. Am. Chem. Soc. 1952, 74, 4138-4140.
3 Choi, P. B.; Williams, C. P.; Buehring, K. G.; McLaughlin, E.; J. Chem. Eng. Data 1985, 30, 403-409.
4 Choi, P. B.; McLaughlin, E.; AIChE J. 1983, 29, 150-153.