The precise astrometric measurements of the Gaia Data Release 2 have opened the door to detailed tests of the predictions of white dwarf cooling models. Significant discrepancies between theory and observations have been identified, the most striking affecting ultramassive white dwarfs. Cheng et al. found that a small fraction of white dwarfs on the so-called Q branch must experience an extra cooling delay of ∼8 Gyr not predicted by current models. ²²Ne phase separation in a crystallizing C/O white dwarf can lead to a distillation process that efficiently transports ²²Ne toward its center, thereby releasing a considerable amount of gravitational energy. Using state-of-the-art Monte Carlo simulations, we show that this mechanism can largely resolve the ultramassive cooling anomaly if the delayed population consists of white dwarfs with moderately above-average ²²Ne abundances. We also argue that ²²Ne phase separation can account for the smaller cooling delay currently missing for models of white dwarfs with more standard compositions.

Gaia Data Release 2 的精确天体测量为白矮星冷却模型预测的详细测试打开了大门。已经确定了理论和观测之间的显着差异，其中影响最大的超大质量白矮星。程等人。发现所谓的 Q 分支上的一小部分白矮星必须经历当前模型无法预测的~8 Gyr 的额外冷却延迟。结晶 C/O 白矮星中的²² Ne 相分离可导致蒸馏过程有效地传输²²Ne 朝向它的中心，从而释放出大量的重力能量。使用最先进的蒙特卡罗模拟，我们表明，如果延迟种群由白矮星组成，其丰度略高于平均水平²² Ne ，则这种机制可以在很大程度上解决超大质量冷却异常。我们还认为，²² Ne 相分离可以解释目前具有更多标准成分的白矮星模型缺少的较小冷却延迟。