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首页> 外文期刊>Astronomy and astrophysics >Post common envelope binaries from SDSS - VIII. Evidence for disrupted magnetic braking
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Post common envelope binaries from SDSS - VIII. Evidence for disrupted magnetic braking

机译：从SDSS-VIII发布公用信封二进制文件。电磁制动中断的证据

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Context. The standard prescription of angular momentum lossin compact binaries assumes magnetic braking to be very efficient aslong as the secondary star has a radiative core, but to be negligibleif the secondary star is fully convective. This prescription has beendeveloped to explain the orbital period gap observed in the orbitalperiod distribution of cataclysmic variables but has so far not beenindependently tested. Because the evolutionary time-scale of postcommon envelope binaries (PCEBs) crucially depends on the rate ofangular momentum loss, a fundamental prediction of the disruptedmagnetic braking theory is that the relative number of PCEBs shoulddramatically decrease for companion-star masses exceeding the mass thatcorresponds to the fully-convective boundary. Aims. We present the results of a large survey of PCEBs amongwhite dwarf/main sequence (WDMS) binaries that allows us to determinethe fraction of PCEBs as a function of secondary star mass andtherewith to ultimately test the disrupted magnetic braking hypothesis.Methods. We obtained multiple spectroscopic observations spreadover at least two nights for 670 WDMS binaries. Systems showing atleast radial velocity variations are considered to be strong PCEB candidates.Taking into account observational selection effects we compare ourresults with the predictions of binary population simulations. Results. Among the 670 WDMS binaries we find 205 strong PCEB candidates. The fraction of PCEBs among WDMS binaries peaks around and steeply drops towards higher mass secondary stars in the range of .Conclusions. The decrease of the number of PCEBs at the fullyconvective boundary strongly suggests that the evolutionary time scalesof PCEBs containing fully convective secondaries are significantlylonger than those of PCEBs with secondaries containing a radiativecore. This is consistent with significantly reduced magnetic windbraking of fully convective stars as predicted by the disruptedmagnetic braking scenario. Key words: binaries: close - magnetic fields - stars: low mass - white dwarfs
机译：上下文。紧凑型双星中角动量损失的标准规定假定，只要副星具有辐射核，电磁制动就会非常有效，但如果副星是完全对流的，则可以忽略不计。已经开发出该处方来解释在催化变化的轨道周期分布中观察到的轨道周期间隙，但是迄今为止尚未进行独立测试。由于后包膜双星（PCEB）的演化时间尺度主要取决于角动量损失的速率，因此，电磁制动理论的基本预测是：对于伴星质量超过对应于其质量的同伴质量，PCEB的相对数量应急剧减少。完全对流边界。目的我们介绍了对白矮星/主序列（WDMS）双星中的PCEB进行的一项大规模调查的结果，该调查使我们能够确定PCEB的分数与次级恒星质量的函数关系，从而最终检验破坏的电磁制动假设。我们获得了至少两个晚上的670个WDMS双星光谱信息。显示至少径向速度变化的系统被认为是强大的PCEB候选者。考虑到观测选择效应，我们将我们的结果与二元人口模拟的预测进行了比较。结果。在670个WDMS二进制文件中，我们发现205个强PCEB候选者。 WDMS双星中PCEB的比例在范围内达到峰值，然后朝着质量较高的副星急剧下降。完全对流边界处PCEB数量的减少强烈表明，具有完全对流次级的PCEB的进化时间尺度比具有次级具有辐射核心的PCEB的进化时间长得多。这与完全对流恒星的磁风制动作用明显降低是一致的，这是由中断的电磁制动情况所预测的。关键词：双星：近-磁场-星：低质量-白矮星

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