The Sirius System and Its Astrophysical Puzzles: Hubble Space Telescope and Ground-based Astrometry
The Sirius System and Its Astrophysical Puzzles: Hubble Space Telescope and Ground-based Astrometry
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天狼星系统及其天体物理难题：哈勃太空望远镜和地面天体测量
DOI：
10.3847/1538-4357/aa6af8
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
D. Gudehus
中科院分区：
文献类型：
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作者：
H. Bond;H. E. Bond;Gail Schaefer;Ronald L. Gilliland;Ronald L. Gilliland;J. Holberg;Brian D. Mason;I. W. Lindenblad;M. Seitz;W. D. Arnett;P. Demarque;F. Spada;Patrick A. Young;M. Barstow;M. Burleigh;D. Gudehus
天狼星，距离我们第七近的恒星系统，是一个视觉双星，包含金属线A1 V星天狼星a，天空中最亮的恒星，以50.13年的周期被最亮和最近的白矮星天狼星B所环绕。利用哈勃太空望远镜（HST）近20年来获得的图像，以及近20年的摄影观测和近2300次可追溯到19世纪的历史测量，我们确定了视觉双星的精确轨道元素。结合视差和A分量的运动，这些元素分别得到天狼星A和天狼星B的动态质量。我们精确的HST天体测量排除了第三个天体围绕系统中任何一颗恒星运行，质量低至15 -。天狼星B在赫茨普龙-罗素图中的位置与其动力质量WDs的理论冷却轨迹非常吻合，并暗示其冷却年龄为~ 126myr。天狼星B在质量半径平面上的位置也与WD理论一致，假设其核心是碳氧。包括假设的祖先在wd之前的进化时间尺度，天狼星B的总年龄约为228±10 Myr。我们使用两个独立的代码计算了具有天狼星A动态质量的恒星的演化轨迹。我们发现有必要假设金属丰度略低于太阳，约为，以适应其在光度-半径平面上的位置。根据这些模型，天狼星A的年龄约为237-247 Myr，不确定度为±15 Myr，与WD伴星的年龄一致。我们讨论了天狼星系统带来的天体物理学难题，包括这两颗恒星过去一定有相互作用的可能性，尽管没有直接的证据证明这一点，而且轨道偏心率仍然很高。
Sirius, the seventh-nearest stellar system, is a visual binary containing the metallic-line A1 V star Sirius A, the brightest star in the sky, orbited in a 50.13 year period by Sirius B, the brightest and nearest white dwarf (WD). Using images obtained over nearly two decades with the Hubble Space Telescope (HST), along with photographic observations covering almost 20 years and nearly 2300 historical measurements dating back to the 19th century, we determine precise orbital elements for the visual binary. Combined with the parallax and the motion of the A component, these elements yield dynamical masses of and for Sirius A and B, respectively. Our precise HST astrometry rules out third bodies orbiting either star in the system, down to masses of ∼15– . The location of Sirius B in the Hertzsprung–Russell diagram is in excellent agreement with theoretical cooling tracks for WDs of its dynamical mass, and implies a cooling age of ∼126 Myr. The position of Sirius B on the mass–radius plane is also consistent with WD theory, assuming a carbon–oxygen core. Including the pre-WD evolutionary timescale of the assumed progenitor, the total age of Sirius B is about 228 ± 10 Myr. We calculated evolutionary tracks for stars with the dynamical mass of Sirius A, using two independent codes. We find it necessary to assume a slightly subsolar metallicity, of about , to fit its location on the luminosity–radius plane. The age of Sirius A based on these models is about 237–247 Myr, with uncertainties of ±15 Myr, consistent with that of the WD companion. We discuss astrophysical puzzles presented by the Sirius system, including the probability that the two stars must have interacted in the past, even though there is no direct evidence for this and the orbital eccentricity remains high.