Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work
Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work
复制标题
DOI：
10.1093/mnras/stw1203
复制
发表时间：
2016-06
影响因子：
4.8
通讯作者：
M. Bours;M. Bours;T. Marsh;S. Parsons;V. Dhillon;Richard Ashley;J. Bento;E. Breedt;T. Butterley;Claudio Caceres;P. Chote;C. Copperwheat;L. Hardy;J. Hermes;P. Irawati;P. Kerry;D. Kilkenny;S. Littlefair;M. Mcallister;S. Rattanasoon;S. Rattanasoon;D. Sahman;Maja Vučković;Richard W. Wilson
中科院分区：
文献类型：
--
作者：
M. Bours;M. Bours;T. Marsh;S. Parsons;V. Dhillon;Richard Ashley;J. Bento;E. Breedt;T. Butterley;Claudio Caceres;P. Chote;C. Copperwheat;L. Hardy;J. Hermes;P. Irawati;P. Kerry;D. Kilkenny;S. Littlefair;M. Mcallister;S. Rattanasoon;S. Rattanasoon;D. Sahman;Maja Vučković;Richard W. Wilson
我们提出了一个长期的计划，时间的白色矮星的食近双星测量表观和/或真实的变化，其轨道周期。我们的计划包括67个密近双星，包括分离和半分离的，其次是M矮星，K矮星，棕矮星或白色矮星。我们总共观测到超过650次白色矮星日食。我们使用这个样本来搜索轨道周期变化，并旨在确定这些变化的根本原因。我们发现，观测轨道周期变化的概率显着增加与观测基线。特别是，所有基线超过10年的双星，光谱类型为K2 - M5.5的秒数，显示出日食到达时间的变化，在大多数情况下达到几分钟。此外，在基线短于10年的双星中，晚光谱型（>M6）、棕矮星或白色矮星的双星似乎没有轨道周期变化。这与所谓的阿普尔盖特机制（Applegate mechanism）相一致，阿普尔盖特机制提出，次级恒星的磁循环可以驱动双星轨道的变化。我们还提出了新的日食时间的NN Ser，这仍然是兼容的先前公布的环双星行星系统模型，虽然只有一个二次项的星历。最后，我们的结论是，我们是有限的相对较短的观测基线的许多双星在日食计时计划，因此，还不能得出可靠的结论，轨道周期变化的原因在进化，白色矮双星。
We present a long-term programme for timing the eclipses of white dwarfs in close binaries to measure apparent and/or real variations in their orbital periods. Our programme includes 67 close binaries, both detached and semi-detached and with M-dwarfs, K-dwarfs, brown dwarfs or white dwarfs secondaries. In total, we have observed more than 650 white dwarf eclipses. We use this sample to search for orbital period variations and aim to identify the underlying cause of these variations. We find that the probability of observing orbital period variations increases significantly with the observational baseline. In particular, all binaries with baselines exceeding 10 yr, with secondaries of spectral type K2 – M5.5, show variations in the eclipse arrival times that in most cases amount to several minutes. In addition, among those with baselines shorter than 10 yr, binaries with late spectral type (>M6), brown dwarf or white dwarf secondaries appear to show no orbital period variations. This is in agreement with the so-called Applegate mechanism, which proposes that magnetic cycles in the secondary stars can drive variability in the binary orbits. We also present new eclipse times of NN Ser, which are still compatible with the previously published circumbinary planetary system model, although only with the addition of a quadratic term to the ephemeris. Finally, we conclude that we are limited by the relatively short observational baseline for many of the binaries in the eclipse timing programme, and therefore cannot yet draw robust conclusions about the cause of orbital period variations in evolved, white dwarf binaries.