The initial–final mass relation (IFMR) links the birth mass of a star to the mass of the compact remnant left at its death. While the relevance of the IFMR across astrophysics is universally acknowledged, not all of its fine details have yet been resolved. A new analysis of a few carbon–oxygen white dwarfs in old open clusters of the Milky Way led us to identify a kink in the IFMR, located over a range of initial masses, 1.65 ≲ M_i/M_⊙ ≲ 2.10. The kink’s peak in white dwarf mass of about 0.70−0.75 M_⊙ is produced by stars with M_i ≈ 1.8−1.9 M_⊙, corresponding to ages of about 1.8−1.7 Gyr. Interestingly, this peak coincides with the initial mass limit between low-mass stars that develop a degenerate helium core after central hydrogen exhaustion, and intermediate-mass stars that avoid electron degeneracy. We interpret the IFMR kink as the signature of carbon star formation in the Milky Way. This finding is critical to constraining the evolution and chemical enrichment of low-mass stars, and their impact on the spectrophotometric properties of galaxies.

初始-最终质量关系（IFMR）将恒星的诞生质量与恒星死亡时留下的紧密残余的质量联系起来。尽管IFMR在整个天体物理学中的相关性得到了普遍认可，但尚未解决其所有细节。在银河系的老疏散星团几碳氧白矮星的新的分析使我们在IFMR识别扭结，位于在一系列初始质量的1.65  ≲ 中号_我/中号_⊙  ≲  2.10。扭结在约0.70-0.75白矮星质量峰 中号_⊙通过与星制作中号_我 ≈1.8-1.9 中号_⊙，对应的年龄约为1.8-1.7 Gyr。有趣的是，该峰与中心氢耗尽后发育简并的氦核的低质量恒星与避免电子简并的中等质量恒星之间的初始质量极限一致。我们将IFMR扭结解释为银河系中碳星形成的标志。这一发现对于限制低质量恒星的演化和化学富集及其对星系分光光度特性的影响至关重要。