Measuring M dwarf winds with DAZ white dwarfs
Measuring M dwarf winds with DAZ white dwarfs
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DOI：
10.1086/508132
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发表时间：
2006-11-20
影响因子：
4.9
通讯作者：
Debes, John H.
中科院分区：
文献类型：
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作者：
Debes, John H.
氢气大气层中的白矮星带有金属线，也就是所谓的DAZ，它们显示出物质在其表面持续积累的证据。众所周知，一些DAZ有未分辨的M矮星伴星，这可以解释通过恒星风观测到的吸积。我将观测到的DAZ的钙丰度与它们的M矮星伴星的轨道分离信息结合起来，推断出M矮星的质量损失率。我发现，对于已知的六个有M个矮星伴星的DAZ中的三个，恒星风可以合理地解释观测到的白矮星上的吸积，假设太阳丰度恒星风的Bondi-Hoyle增量在10(-14)到10(-16)M圆点yr(-1)的数量级上。样品的其余部分有伴随轨道>；=1AU，并且需要伴随质量损失率为>；10(-11)M圆点yr(-1)。我的结论是，在相隔很远的同伴的情况下，肯定有另一种解释可以解释DAS上的物质积累。其中两颗近距离双星的推算风比红矮星-白矮星对由于恒星风的磁力制动而造成的角动量损失的典型假设要小几个数量级，并可能严重影响对低质量伴星CVs形成速度的预测。
Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, show evidence for ongoing accretion of material onto their surfaces. Some DAZs are known to have unresolved M dwarf companions, which could account for the observed accretion through a stellar wind. I combine observed Ca abundances of the DAZs with information on the orbital separation of their M dwarf companions to infer the mass-loss rate of the M dwarfs. I find that for three of the six known DAZs with M dwarf companions, a stellar wind can plausibly explain the observed accretion on the white dwarfs assuming Bondi-Hoyle accretion of solar abundance stellar winds on the order of 10(-14) to 10(-16) M-circle dot yr(-1). The rest of the sample have companions with orbits >= 1 AU and require companion mass-loss rates of > 10(-11) M-circle dot yr(-1). I conclude that there must be an alternative explanation for accretion of material onto DAZs with widely separated companions. The inferred winds for two of the close binaries are orders of magnitude smaller than typically assumed for the angular momentum loss of red dwarf-white dwarf pairs due to magnetic braking from a stellar wind and may seriously affect predictions for the formation rate of CVs with low-mass companions.