On the initial-final mass relation and maximum mass of white dwarf progenitors

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Abstract
The four white dwarfs (WDs) discovered in the young open cluster NGC 2516 are crucial in defining the shape of the initial-final mass relation (IFMR) and upper mass limit for WD progenitors (Mwd). The cluster metallicity has been recently determined as [M/H] = −0.32 ± 0.06, which is found to decrease the previously derived WD progenitor masses by 1.0–1.7 M⊙. The new progenitor masses are consistent with Mwd of only 5–6 M⊙, which is confirmed by integrating an extrapolated cluster mass function. The results disagree with the 8-M⊙ upper limit contained in the frequently used semi-empirical IFMR of Weidemann, but are now in agreement with evolutionary models with moderate core over- shoot. It is suggested that beyond an initial mass of 3M⊙, the IFMR may follow the relationship between initial mass and the core mass at the start of the thermally pulsating asymptotic giant branch, implying very efficient mass loss. According to these evolutionary models, non-degenerate carbon burning is possible in the cores of stars with initial mass ⊙, so a similar Mwd means there should be few carbon deflagration supernovae. However, decreasing Mwd from 8 to 5–6 M⊙ would significantly increase the expected numbers of core-collapse supernovae.

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