发表机构
Anton Pannekoek Instituut voor Sterrenkunde, Universiteit van Amsterdam; Central Michigan University（阿姆斯特丹大学安东·潘内科克天文研究所; 中密歇根大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究确定O型巨星英仙座ξ的自转周期为2.040514(20)天，发现其存在弱全局表面磁场，解释了其周期与循环变异性共存的现象。
AI 中文摘要
OB型恒星呈现谱线轮廓变异性，常与自转相关；尤其在对紫外风敏感的谱线中，离散吸收成分往往周期性重现。我们对O7.5III(n)((f))型恒星英仙座ξ（ξ Persei）形成于极靠近恒星处的光谱区域开展了周期性搜索，确定N IV 1718 Å谱线为受干扰最小的谱线，且拥有大而均匀的可用数据集：包括12年间获取的307条IUE光谱，以及21年后获取的11条STIS光谱。我们还研究了322条时间分辨的He II 4686 Å光谱，以及覆盖13年的MOST、BRITE和TESS空间测光数据，同时重新分析了钱德拉（Chandra）的X射线研究数据。对该区域流量进行CLEAN分析及后续加权最小二乘拟合，得到唯一的自转周期2.040514(20)天。N IV、Si IV、Hα和He II谱线轮廓的流量最大值相位与X射线变异性研究结果一致，且该周期也在测光数据中被发现。鉴于探测恒星表面附近风区域的相干周期性行为，我们提出英仙座ξ拥有一颗迄今未被探测到的弱全局表面磁场。正弦行为表明仅可见一个磁极，倾角i≈51°，磁倾角为39°。我们提出一个概念框架，其中全局磁场对风的弱约束可形成小型磁层盘，同时允许在更高磁纬度形成更经典的共转相互作用区；周期性变异性可理解为磁层盘在自转相位下，沿视线方向和恒星边缘外变化的投影面积所导致。
英文摘要
OB stars exhibit line profile variability, often associated with rotation; notably, in their UV wind-sensitive lines where discrete absorption components tend to recur cyclically. We searched for periodicity in spectral regions of the O7.5III(n)((f)) star xi Persei formed very close to the star. The NIV 1718 A line was identified as the most uncontaminated spectral with a large and homogeneous available dataset is available: 307 IUE spectra over 12 years and 11 STIS spectra taken 21 years later. We also studied 322 time-resolved HeII 4686 A spectra and MOST, BRITE, and TESS space photometry, covering a time span of 13 years. We also reconsidered X-ray studies with Chandra. A CLEAN analysis and subsequent weighted least-squares fit of the flux in this region resulted in a unique period of 2.040514(20) d, attributed to rotation. The phase of maximum flux in the NIV, SiIV, Ha, and HeII line profiles coincide with the results of X-ray variability studies. This period was also found in the photometric data. Given the coherent periodic behaviour probing the region of the wind nearest the stellar surface, we propose that xi Per has an as-yet undetected weak global surface magnetic field. The sinusoidal behaviour suggested that only one magnetic pole is visible, implying an inclination of i approximately 51 deg, and therefore, 39 deg for the magnetic obliquity. We present a conceptual framework within which weak wind confinement by a global magnetic field can create a small magnetospheric disc, while allowing for the formation of more classic corotating interaction regions at higher magnetic latitudes. The periodic variations are then understood to result from the changing projected area of the magnetospheric disc as a function of rotational phase, both along the line of sight and off the stellar limb.
Comments20 pages, 20 figures
Journal refAA57678-25, 2026, A&A, 714, A63
DOI：10.1051/0004-6361/202557678
