Pollux is considered as an archetype of a giant star hosting a planet: its radial velocity (RV) presents sinusoidal variations with a period of about 590 d, which have been stable for more than 25 years. Using ESPaDOnS and Narval we have detected a weak (sub-gauss) magnetic field at the surface of Pollux and followed up its variations with Narval during 4.25 years, i.e. more than for two periods of the RV variations. The longitudinal magnetic field is found to vary with a sinusoidal behaviour with a period close to that of the RV variations and with a small shift in phase. We then performed a Zeeman Doppler imaging (ZDI) investigation from the Stokes V and Stokes I least-squares deconvolution (LSD) profiles. A rotational period is determined, which is consistent with the period of variations of the RV. The magnetic topology is found to be mainly poloidal and this component almost purely dipolar. The mean strength of the surface magnetic field is about 0.7 G. As an alternative to the scenario in which Pollux hosts a close-in exoplanet, we suggest that the magnetic dipole of Pollux can be associated with two temperature and macroturbulent velocity spots which could be sufficient to produce the RV variations. We finally investigate the scenarii of the origin of the magnetic field which could explain the observed properties of Pollux.
Eating planets makes you younger: The magnetic dynamo rejuvenation of GJ 504 by planetary engulfment
Leiden University（莱顿大学）；Université de Toulouse（图卢兹大学）；CNRS（法国国家科学研究中心）；Université de Liège（列日大学）；Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；University of Oslo（奥斯陆大学）；Eberhard-Karls Universität Tübingen（蒂宾根大学）
Centro de Astrobiología, CSIC-INTA（天体生物学中心，CSIC-INTA）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Departamento de Astrofísica, Universidad de La Laguna（拉帕尔马大学天体物理学系）；Consejo Superior de Investigaciones Científicas (CSIC)（西班牙国家研究委员会（CSIC））；INAF – Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；IFPU – Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；INFN – National Institute for Nuclear Physics（意大利国家核物理研究所）；INAF – Osservatorio Astronomico di Palermo（意大利国家天体物理研究所巴勒莫天文台）；Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto（波尔图大学空间天体物理学与天体科学研究所）
The attempted polarity reversal and evolving magnetic environment of AD Leo
Leiden University（莱顿大学）；University of Queensland（昆士兰大学）；University of Oslo（奥斯陆大学）；Université de Toulouse（图卢兹大学）；Université de Montpellier（蒙彼利埃大学）；Macquarie University（麦考瑞大学）
AD Leo磁场未发生极性反转，但其大尺度磁场呈现轴对称的极性双极结构，且恒星质量损失率比太阳高一个数量级，宜居带位于阿尔芬面之外。
