γ Dor型脉动星的首次偏振光谱巡测结果
Results from the first spectropolarimetric survey of $γ$ Dor pulsators
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中文总结 AI 辅助
本研究通过TESS数据确认γ Dor型脉动星并对47颗开展偏振光谱巡测，发现3颗疑似强磁场星均非真正γ Dor型脉动星，未在其余天体中探测到强表面磁场，得出强全局磁场或与γ Dor型脉动互斥的结论。
中文摘要 AI 辅助
背景：磁场对恒星结构与演化有重要影响。在中等质量的A型与F型恒星中，已有大量恒星被直接测量到存在强的、全局有序的磁场，也存在弱和/或小尺度可变磁场的迹象；但在中等质量的γ Dor型脉动星中，尚未发现存在强表面磁场的恒星。目标：本研究的总体目标是搜寻γ Dor型脉动星表面存在强的、全局有序磁场的证据。方法：基于对凌日系外行星巡天卫星（TESS）任务的空间测光数据的分析，我们确认了符合γ Dor型脉动星特征的天体；随后对其中47个天体开展偏振光谱巡测，其精度足以探测偶极表面磁场，探测阈值低至约10至100高斯。结果：我们在3个目标中探测到强磁场，但经仔细核查，这些天体均非真正的γ Dor型脉动星；其余44个天体中，未发现任何表面磁场的证据。结论：我们得出结论，要么强的、全局有序磁场与γ Dor型脉动是互斥的，要么这类恒星极为罕见；一种可能的解释是，强全局磁场会抑制激发机制，阻止强磁场中等质量恒星中γ Dor型脉动的产生。我们为该样本推导的偶极表面磁场强度上限（≤50至100高斯），为包含磁场的γ Dor型脉动星星震模型的表面边界条件提供了重要约束。
英文摘要
Context. Magnetic fields can have an important influence on stellar structure and evolution. In intermediate-mass (A- and F-type) stars, there are many known stars with directly measured strong, globally organized magnetic fields, as well as indications of weak and/or small-scale variable fields. However, among the intermediate-mass $γ$ Dor pulsators, there are no known stars with strong surface magnetic fields. Aims. The broad goal of this work is to search for evidence of strong, globally organized fields at the surface of $γ$ Dor pulsators. Methods. We identified objects consistent with being $γ$ Dor pulsators based on an analysis of space photometry from the Transiting Exoplanet Survey Satellite (TESS) mission. A spectropolarimetric survey was then conducted on a subset of 47 of these objects, with a precision sufficient to detect dipolar surface magnetic fields down to a threshold of about 10 -- 100 G. Results. We detected strong magnetism in three targets. However, upon closer inspection, none of these appear to be genuine $γ$ Dor pulsators. We found no evidence of surface magnetism in any of the remaining 44 objects. Conclusions. We conclude that either strong, globally organized magnetic fields and $γ$ Dor pulsation are mutually exclusive, or that such stars are exceedingly rare. A possible explanation is that strong global fields inhibit the excitation mechanism, which prevents $γ$ Dor pulsations from being driven in strongly magnetic intermediate-mass stars. The dipolar surface magnetic field strength upper limits we derive for this sample ($\lesssim$ 50 -- 100 G) provide valuable constraints for surface boundary conditions for asteroseismic models that include magnetism for $γ$ Dor stars.
