Magnetic fields in stars are mass dependent. Lower-mass stars like the Sun sustain a magnetic field, but only about 7% of the massive stars (with eight or more solar masses) have large-scale surface magnetic fields. The origin of such magnetic fields is unclear. Abigail Frost and colleagues investigate a binary system of two massive stars (HD 148937) using interferometric and spectroscopic methods, finding that one star has a detectable magnetic field while the other does not. The results support the scenario that the primary star is the product of a binary merger within an originally triple system and the magnetic field is generated in the merger process.

The analysis uses data from the Precision Integrated-Optics Near-Infrared Imaging Experiment (PIONIER) and the GRAVITY instrument of the Very Large Telescope Interferometer (VLTI) at Paranal Observatory in Chile. The interferometric data suggests that Balmer emission, an indirect signature of stellar winds confined by magnetic fields, is coming from the primary star. Masses, velocities, and temperatures of the stars are extracted from parameters of orbital motion and the interferometric observations.

恒星的磁场取决于质量。像太阳这样的低质量恒星会维持磁场，但只有约 7% 的大质量恒星（质量为太阳质量的 8 倍或以上）具有大规模表面磁场。此类磁场的起源尚不清楚。Abigail Frost 和同事使用干涉和光谱法研究了一个由两颗大质量恒星组成的双星系统（HD 148937），发现其中一颗恒星具有可探测的磁场，而另一颗则没有。结果支持了这样的假设：主恒星是原本是三重系统内的双星合并的产物，磁场是在合并过程中产生的。

该分析使用了来自智利帕拉纳尔天文台精密集成光学近红外成像实验（PIONIER）和甚大望远镜干涉仪（VLTI）重力仪器的数据。干涉数据表明，巴尔默发射是受磁场限制的恒星风的间接特征，来自主恒星。恒星的质量、速度和温度是从轨道运动参数和干涉观测中提取的。