The Rapid Rotation of the Strongly Magnetic Ultramassive White Dwarf EGGR 156
The Rapid Rotation of the Strongly Magnetic Ultramassive White Dwarf EGGR 156
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DOI：
10.3847/1538-3881/ac8543
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发表时间：
2022-07
期刊：
影响因子：
--
通讯作者：
K. Williams;J. Hermes;Z. Vanderbosch
中科院分区：
文献类型：
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作者：
K. Williams;J. Hermes;Z. Vanderbosch
白矮星自转周期的分布为限制恒星演化后期的角动量演化提供了一种手段，也为了解双简并合并的物理和残余提供了一种手段。尽管低质量白矮星的旋转分布受到星震学的相对较好的限制，但由中等质量恒星演化或白矮星合并产生的高质量白矮星的旋转分布则不然。由于斑点恒星的旋转而导致的白矮星的光度变化正在迅速增加具有测量的旋转周期的高质量白矮星的样本大小。我们发现了 EGGR 156（一颗强磁性超大质量白矮星）光变曲线中 22.4 分钟的光度变化。我们将这种变异性解释为快速旋转，并且我们的数据表明 EGGR 156 是双简并合并的残余物。最后，我们计算了由于磁偶极子辐射而导致的快速旋转、大质量、磁性 WD 的周期变化率。在许多情况下，包括 EGGR 156，目前在合理的时间尺度内无法检测到周期变化，这表明这些 WD 可能是非常精确的时钟。对于磁性最强、旋转速度最快的大质量 WD，例如 ZTF J1901+1450 和 RE J0317−853，周期变化应该是可检测到的，并且可能有助于限制这些奇异白矮星的结构和演化。
The distribution of white dwarf rotation periods provides a means for constraining angular momentum evolution during the late stages of stellar evolution, as well as insight into the physics and remnants of double degenerate mergers. Although the rotational distribution of low-mass white dwarfs is relatively well constrained via asteroseismology, that of high-mass white dwarfs, which can arise from either intermediate-mass stellar evolution or white dwarf mergers, is not. Photometric variability in white dwarfs due to rotation of a spotted star is rapidly increasing the sample size of high-mass white dwarfs with measured rotation periods. We present the discovery of 22.4 minute photometric variability in the light curve of EGGR 156, a strongly magnetic, ultramassive white dwarf. We interpret this variability as rapid rotation, and our data suggest that EGGR 156 is the remnant of a double degenerate merger. Finally, we calculate the rate of period change in rapidly-rotating, massive, magnetic WDs due to magnetic dipole radiation. In many cases, including EGGR 156, the period change is not currently detectable over reasonable timescales, indicating that these WDs could be very precise clocks. For the most highly-magnetic, rapidly-rotating massive WDs, such as ZTF J1901+1450 and RE J0317−853, the period change should be detectable and may help constrain the structure and evolution of these exotic white dwarfs.