Complex magnetic topology and strong differential rotation on the low-mass T Tauri star V2247 Oph
Complex magnetic topology and strong differential rotation on the low-mass T Tauri star V2247 Oph
复制标题
DOI：
10.1111/j.1365-2966.2009.15998.x
复制
发表时间：
2009-11
影响因子：
4.8
通讯作者：
J. Donati;M. Skelly;J. Bouvier;M. Jardine;S. Gregory;J. Morin;G. Hussain;C. Dougados;F. Ménard;Y. Unruh
中科院分区：
文献类型：
--
作者：
J. Donati;M. Skelly;J. Bouvier;M. Jardine;S. Gregory;J. Morin;G. Hussain;C. Dougados;F. Ménard;Y. Unruh
从观察收集的ESPaDOnS分光偏振计在加拿大-法国-夏威夷望远镜，我们报告的塞曼签名的低质量经典金牛座T星星（cTTS）V2247 Oph的检测。在光球谱线中检测到的轮廓扭曲和圆偏振特征可以被解释为是由星星表面的冷斑和磁区引起的。大尺度磁场强度适中，高度复杂;此外，斑点分布和磁场在仅一周的时间尺度上显示出显著的变化，这可能是强烈的差异旋转的结果。这两种性质使得V2247 Oph与（更大质量的）原型cTTS BP Tau非常不同;我们推测这种差异反映了V2247 Oph的质量较低。在我们的观测过程中，V2247 Oph处于低吸积状态，发射线只显示出弱水平的圆偏振;然而，我们发现过量的发射显然集中在一个强径向场的中纬度地区，这表明它是吸积漏斗的支点。我们在V2247 Oph上报告的更弱和更复杂的场可能与非常低质量的晚M矮星有相似之处，并可能解释为什么低质量的cTTS平均旋转速度比中等质量的快。这些令人惊讶的结果需要来自V2247 Oph和其他类似低质量cTTS的新独立数据集的确认。
From observations collected with the ESPaDOnS spectropolarimeter at the Canada–France–Hawaii Telescope, we report the detection of Zeeman signatures on the low-mass classical T Tauri star (cTTS) V2247 Oph. Profile distortions and circular polarization signatures detected in photospheric lines can be interpreted as caused by cool spots and magnetic regions at the surface of the star. The large-scale field is of moderate strength and highly complex; moreover, both the spot distribution and the magnetic field show significant variability on a time-scale of only 1 week, as a likely result of strong differential rotation. Both properties make V2247 Oph very different from the (more massive) prototypical cTTS BP Tau; we speculate that this difference reflects the lower mass of V2247 Oph. During our observations, V2247 Oph was in a low-accretion state, with emission lines showing only weak levels of circular polarization; we nevertheless find that excess emission apparently concentrates in a mid-latitude region of a strong radial field, suggesting that it is the footpoint of an accretion funnel. The weaker and more complex field that we report on V2247 Oph may share similarities with those of very-low-mass late-M dwarfs and potentially explain why low-mass cTTSs rotate on average faster than intermediate-mass ones. These surprising results need confirmation from new independent data sets on V2247 Oph and other similar low-mass cTTSs.