Plateaus, dips, and rebrightenings during the outbursts of WZ Sge: no magnetic propeller, but a veiling curtain
Plateaus, dips, and rebrightenings during the outbursts of WZ Sge: no magnetic propeller, but a veiling curtain
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WZ Sge爆发期间的高原、低谷和重新增亮：没有磁力螺旋桨，但有帷幕
DOI：
10.1093/mnras/stac116
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发表时间：
2022
影响因子：
4.8
通讯作者：
Georganti M
中科院分区：
文献类型：
--
作者：
Georganti M
WZ Sge是高度演化、低吸积速率的矮新星（DNe）的原型。在从爆发下降，它的光变曲线显示一个“下降”，然后是1000年的“回声爆发”。标准的盘不稳定性模型没有考虑这种行为，这也是在其他低吸积率DNe。最近对这些快速亮度变化的一种解释是，它们代表了磁螺旋桨状态的转变。在这里，我们用哈勃太空望远镜拍摄的时间分辨的紫外光谱来测试这种情况，就在2001年WZ Sge火山爆发之前，期间和之后。我们没有发现任何独特的或独特的签名，可以归因于螺旋桨的时间平均紫外光谱或变异光谱。因此，数据不支持磁螺旋桨的情况。我们的研究并没有解决WZ Sge的爆发光变曲线之谜，实际上增加了另一个：在所有爆发阶段看到的窄吸收特征的起源。我们明确地表明，这些功能很可能形成在一个高密度的“面纱幕”的特征温度。然而，这种面纱的性质和起源尚不清楚。鉴于WZ Sge型DNe是最常见的吸积白色矮星，解决这些问题应该是一个高度优先事项。
WZ Sgeis the prototype of highly evolved, low-accretion rate dwarf novae (DNe). During the decline from eruptions, its light curve displays a ‘dip’ followed by ≃10 ‘echo outbursts’. The standard disc instability model does not account for this behaviour, which is also seen in other low-accretion rate DNe. One recent interpretation for these rapid brightness changes is that they represent transitions into and out of a magnetic propeller regime. Here, we test this scenario with time-resolved, ultraviolet spectroscopy taken with theHubble Space Telescopejust before, during and after the dip inWZ Sge’s 2001 eruption. We find no distinctive or unique signatures that could be attributed to a propeller in either the time-averaged UV spectrum or the variability spectrum. Thus the data do not support the magnetic propeller scenario. Instead of resolving the mystery ofWZ Sge’s outburst light curve, our study has actually added another: the origin of the narrow absorption features seen in all outburst phases. We show explicitly that these features are likely formed in a high-density ‘veiling curtain’ with a characteristic temperature. However, the nature and origin of this veil are unclear. Given thatWZ Sge-type DNe are the most intrinsically common class of accreting white dwarfs, resolving these questions should be a high priority.