发表机构
European Organisation for Astronomical Research in the Southern Hemisphere (ESO); Georgia State University; Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS; Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas（欧洲南方天文台; 佐治亚州立大学; 蔚蓝海岸大学，蔚蓝海岸天文台，法国国家科学研究中心; 圣保罗大学，天文学、地球物理学和大气科学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对新发现的壳Be星+sdOB双星AN Col，结合GRAVITY干涉测量与光谱视向速度，给出完整三维轨道解，测得动力学质量M_Be=8.39±0.67 M☉、M_sdOB=0.81±0.22 M☉，并揭示其高转移效率与伴星温度接近30 kK。
AI 中文摘要
AN Col是一颗壳Be星，其光谱中出现了由热、演化伴星引起的瞬态光谱特征，伴星轨道周期为数月。如果得到确认，这将使其跻身于日益增多的后质量转移自转增快Be星+剥离亚矮星OB型（sdOB）双星之列。刻画双星轨道有助于获得动力学质量，为双星演化和质量转移模型提供罕见的锚点。我们给出了新发现的Be+sdOB双星AN Col的完整三维轨道解、动力学质量和动力学视差。作为获得可靠轨道解的前提，我们需要刻画盘宽密度振荡周期，该周期主导了主要的光谱周期，以便分离较弱的周期轨道变化。我们利用GRAVITY的近红外干涉时间序列来确认伴星并绘制相对天体测量轨道。在已知轨道周期的前提下，我们识别出追踪两恒星分量各自轨道的谱线，并测量其视向速度，从而获得双线光谱轨道。结合干涉测量和光谱测量，我们推导出完整的三维轨道解。该盘自2010年以来已完成三个完整的振荡周期，周期长度约为5.1年。约87.7天的轨道与侧向取向相容，但TESS光变曲线中缺乏掩食现象将轨道倾角限制在88.4°或更小。所得质量为M_Be = 8.39±0.67太阳质量，M_sdOB = 0.81±0.22太阳质量。与其他Be+sdOB双星一样，过去质量转移的效率估计值出乎意料地高。探测到来自伴星的弱He II 4686吸收线和其它He I线，表明其有效温度接近30 kK，且为慢自转星。
英文摘要
AN~Col is a shell Be star that has shown transient spectral features caused by a hot, evolved companion on a months-long orbit. If confirmed, this would place it among the growing category of post-mass-transfer spun-up Be + stripped subdwarf OB-type (sdOB) binaries. Characterizing the binary orbit enables obtaining dynamical masses, to provide a rare anchor for models of binary evolution and mass transfer. We present a full 3-dimensional orbital solution, dynamical masses, and dynamical parallax, for the newly discovered Be + sdOB binary AN~Col. As a prerequisite to obtain a reliable orbital solution, we need to characterize the disk-wide density oscillation cycle that gives rise to the dominant spectroscopic cycles in order to separate the weaker periodic orbital variations. We use near-IR interferometry time series from GRAVITY to confirm the companion and to map the relative astrometric orbit. With the knowledge of the orbital period, we identify spectral lines that trace the orbit of each of the two stellar components and we measure their radial velocities to obtain a double-lined spectroscopic orbit. Combining interferometry and spectroscopy, we derive the full 3-dimensional orbital solution. The disk has completed three full oscillation cycles since 2010, with a cycle length of ~5.1 yr. The ~87.7-day orbit is compatible with edge-on orientation, but the lack of eclipses in TESS light curves limits the orbital inclination to 88.4$^{\circ}$ or less. The resulting masses are $M_{\rm Be} = 8.39\pm0.67$ Msun and $M_{\rm sdOB} = 0.81\pm0.22$ Msun. As in other Be + sdOB binaries, the estimated efficiency of the past mass transfer is unexpectedly high. Detection of a weak \spec{He}{ii}{4686} absorption and other \ion{He}{i} lines from the companion indicates that its effective temperature is close to 30 kK, and that it is a slow rotator. [abstract continues but no space left...]
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