P–K_s diagram combining our Gaia DR2 results for the LMC with observations of supergiants in M 31 and M 33 by Ren et al. (2019). Stars from Ren et al. (2019) are indicated according to the pulsation mode given there, namely open symbols for first overtone pulsators and filled symbols for stars pulsating in fundamental mode. Long secondary periods are delineated with crosses. First overtone (thin lines) and fundamental mode (thick lines) periods from RSG pulsation models by Guo & Li (2002) are also shown, for a few different values of mass.