Period-M_bol relation. Error bars in M_bol are plotted but are typically smaller than the symbol size. LMC objects are plotted as open squares, SMC objects are filled squares. Blue symbols indicate the six CCs in EBs. One outlier is marked by a red cross and is identified. The black line indicates the best fit (excluding the outlier) to the complete MC sample. Fits to the LMC and SMC stars separately are given in the text. The blue line gives the PL relation for MW CCs from G20, while the red line gives the recommended solution for T2C (Groenewegen 2020a).