IFMR relation for white dwarfs in the open cluster M37. The red symbol indicates the PN central star WD1 and the green symbol WD2 from our study. The other white dwarfs are from Cummings et al. (2018). The blue graph, taken from that paper, is the semi-empirical three-piece linear fit to white dwarfs in several open clusters based on PARSEC isochrones. The vertical arrow points to the current M37 progenitor mass at the tip of the AGB.