MOVES行星宿主星HD189733的演化磁场
MOVES I. The evolving magnetic field of the planet-hosting star HD189733
摘要：
HD 189733是一颗活跃的K矮星，它的凌日热木星是研究最多的系外行星系统之一。在这篇论文中的第一个多波长观测的eVaporating系外行星和它的恒星（MOVES）计划，我们提出了一个为期2年的监测大尺度磁场的HD 189733。使用塞曼多普勒成像，对五个观测时期（即2013年6月至7月、2013年8月、2013年9月、2014年9月和2015年7月）的磁图进行了重建。我们表明，该领域的演变沿五个历元，总磁场的平均值为36，41，42，32和37 G，分别。所有的历元都显示出一个环面主导的场。利用Moutou等人2007年和Fares等人2010年发表的数据，我们能够研究磁场在9年内的演变，这是给定恒星最长的监测活动之一。虽然在所观察到的时期的字段演变，没有极性开关的两极进行了观察。利用位场源面外推技术计算了行星所在位置的恒星磁场值。我们表明，行星的磁环境是不均匀的轨道，它的观测时期之间的变化，由于恒星磁场的演变。这一结果强调了同时期多波长观测对太阳系外行星系统的重要性。我们重建的地图是我们MOVES多波长观测的解释和建模的关键输入。
英文摘要：
HD189733 is an active K dwarf that is, with its transiting hot Jupiter, among the most studied exoplanetary systems. In this first paper of the Multiwavelength Observations of an eVaporating Exoplanet and its Star (MOVES) program, we present a 2-year monitoring of the large-scale magnetic field of HD189733. The magnetic maps are reconstructed for five epochs of observations, namely June-July 2013, August 2013, September 2013, September 2014, and July 2015, using Zeeman-Doppler Imaging. We show that the field evolves along the five epochs, with mean values of the total magnetic field of 36, 41, 42, 32 and 37 G, respectively. All epochs show a toroidally-dominated field. Using previously published data of Moutou et al. 2007 and Fares et al. 2010, we are able to study the evolution of the magnetic field over 9 years, one of the longest monitoring campaign for a given star. While the field evolved during the observed epochs, no polarity switch of the poles was observed. We calculate the stellar magnetic field value at the position of the planet using the Potential Field Source Surface extrapolation technique. We show that the planetary magnetic environment is not homogeneous over the orbit, and that it varies between observing epochs, due to the evolution of the stellar magnetic field. This result underlines the importance of contemporaneous multi-wavelength observations to characterise exoplanetary systems. Our reconstructed maps are a crucial input for the interpretation and modelling of our MOVES multi-wavelength observations.
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