We assume that the strong convection during core helium flash of low mass red giant branch (RBG) stars excite waves that propagate to the envelope, and find that the energy that these waves deposit in the envelope causes envelope expansion and brightening. We base our assumption and the estimate of the waves’ energy on studies that explored such a process due to the vigorous core convection of massive stars just before they experience a core collapse supernova explosion. Using the stellar evolutionary code mesa, we find that the waves’ energy causes an expansion within few years by tens to hundreds solar radii. Despite the large brightening, we expect the increase in radius and luminosity to substantially enhance mass-loss rate and dust formation. The dust shifts the star to become much redder (to the infrared), and the star might actually become fainter in the visible. The overall appearance is of a faint red transient event that lasts for months to few years. We suggest that in some cases envelope expansion might lead stars that are about to leave the RGB to engulf exoplanets. The extended envelope has a smaller binding energy to a degree that allows planets of several Jupiter masses or more and brown dwarfs to survive the common envelope evolution. We suggest this scenario to account for the planet orbiting the white dwarf (WD) WD 1856+534 (TIC 267574918) and for the WD–brown dwarf binary system ZTFJ003855.0+203025.5.

中文翻译：

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红巨星在核心氦闪期间通过波传播到包络层和对系外行星的影响而迅速膨胀

我们假设低质量红巨星分支（RBG）恒星核心氦闪期间的强对流激发波传播到包层，并发现这些波在包层中沉积的能量导致包层膨胀和变亮。我们的假设和对波能量的估计是基于对这一过程的研究，该过程是由于大质量恒星在经历核心坍缩超新星爆炸之前的强烈核心对流造成的。使用恒星进化代码台面，我们发现波浪的能量会在几年内导致膨胀数十到数百个太阳半径。尽管亮度较大，但我们预计半径和光度的增加将大大提高质量损失率和尘埃形成。尘埃使恒星变得更红（对红外线），而这颗恒星实际上可能在可见光中变得更暗。整体外观是持续数月至数年的微弱红色短暂事件。我们建议在某些情况下，包络膨胀可能会导致即将离开 RGB 的恒星吞没系外行星。扩展的包层具有较小的结合能，在一定程度上允许几个木星质量或更多质量的行星和褐矮星在共同包层演化中幸存下来。我们建议这种情况来解释围绕白矮星 (WD) WD 1856+534 (TIC 267574918) 运行的行星和 WD-棕矮星双星系统 ZTFJ003855.0+203025.5。扩展的包层具有较小的结合能，在一定程度上允许几个木星质量或更多质量的行星和褐矮星在共同包层演化中幸存下来。我们建议这种情况来解释围绕白矮星 (WD) WD 1856+534 (TIC 267574918) 运行的行星和 WD-棕矮星双星系统 ZTFJ003855.0+203025.5。扩展的包层具有较小的结合能，在一定程度上允许几个木星质量或更多质量的行星和褐矮星在共同包层演化中幸存下来。我们建议这种情况来解释围绕白矮星 (WD) WD 1856+534 (TIC 267574918) 运行的行星和 WD-棕矮星双星系统 ZTFJ003855.0+203025.5。