旋顶Be星Achernar的双星系统
The binary system of the spinning-top Be star Achernar
摘要：
Achernar，最接近和最明亮的经典Be星，呈现旋转变平，重力变暗，偶尔的发射线由于气体盘，和一个扩展的极风。它也是一个有早期A型矮星伴星的密近双星系统的成员。我们的目标是确定的Achernar系统的轨道参数，并估计组件的物理特性。我们使用VLT/VLTI的各种高角分辨率仪器（VISIR，NACO，SPHERE，AMBER，PIONIER，GRAVITY和MATISSE）在13年内（2006-2019）监测了Achernar B的相对位置。这些天体测量观测得到了2003年至2016年期间700多个光谱的补充。我们确定，Achernar B轨道的Be星的7年周期，偏心轨道（e = 0.7255 +/- 0.0014），使两颗恒星在近星点2天文单位。发现Be星的质量为mA = 6.0 +/- 0.6 Msun，次级质量为mB = 2.0 +/- 0.1 Msun。我们发现一个很好的协议Achernar A的参数与6.4 Msun在63万年的年龄临界旋转恒星的演化模型。我们还确定了一个解决comoving低质量的恒星，这使我们提出，Achernar是杜鹃座，钟表移动组的成员。Achernar A目前处于关闭后的短暂演化阶段，在此期间其几何扁平率最极端。考虑到轨道参数，两个组分之间没有发生显著的相互作用，表明Be星可能通过直接的单星演化路径形成，而没有质量转移。由于A成分将在几十万年后进入不稳定带，阿切纳尔似乎是造父双星系统的一个有希望的祖先。
英文摘要：
Achernar, the closest and brightest classical Be star, presents rotational flattening, gravity darkening, occasional emission lines due to a gaseous disk, and an extended polar wind. It is also a member of a close binary system with an early A-type dwarf companion. We aim to determine the orbital parameters of the Achernar system and to estimate the physical properties of the components. We monitored the relative position of Achernar B using a broad range of high angular resolution instruments of the VLT/VLTI (VISIR, NACO, SPHERE, AMBER, PIONIER, GRAVITY, and MATISSE) over a period of 13 years (2006-2019). These astrometric observations are complemented with a series of more than 700 optical spectra for the period from 2003 to 2016. We determine that Achernar B orbits the Be star on a seven-year period, eccentric orbit (e = 0.7255 +/- 0.0014) which brings the two stars within 2 au at periastron. The mass of the Be star is found to be mA = 6.0 +/- 0.6 Msun for a secondary mass of mB = 2.0 +/- 0.1 Msun. We find a good agreement of the parameters of Achernar A with the evolutionary model of a critically rotating star of 6.4 Msun at an age of 63 million years. We also identify a resolved comoving low-mass star, which leads us to propose that Achernar is a member of the Tucana-Horologium moving group. Achernar A is presently in a short-lived phase of its evolution following the turn-off, during which its geometrical flattening ratio is the most extreme. Considering the orbital parameters, no significant interaction occurred between the two components, demonstrating that Be stars may form through a direct, single-star evolution path without mass transfer. Since component A will enter the instability strip in a few hundred thousand years, Achernar appears to be a promising progenitor of the Cepheid binary systems.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
