Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity
Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity
复制标题
DOI：
10.1051/0004-6361/201425519
复制
发表时间：
2015-05
期刊：
影响因子：
--
通讯作者：
A. Hatzes;W. Cochran;M. Endl;E. Guenther;P. Macqueen;M. Hartmann;M. Zechmeister;I. Han;B.-C. Le
中科院分区：
文献类型：
--
作者：
A. Hatzes;W. Cochran;M. Endl;E. Guenther;P. Macqueen;M. Hartmann;M. Zechmeister;I. Han;B.-C. Le
我们研究了 20 多年前首次报道的 Alpha Tau 长周期径向速度变化的性质。我们分析了 30 多年来 Alpha Tau 的精确恒星径向速度测量结果。还对 Halpha 和 Ca II 8662 谱线以及依巴谷光度法进行了检查，以帮助辨别长周期径向速度变化的性质。我们的径向速度数据表明，长周期、低振幅径向速度变化是长期且一致的。此外，Halpha 等效宽度测量和依巴谷光度测量显示该时期没有显着变化。对这颗恒星的另一项研究表明，谱线形状随径向速度周期没有变化。轨道解得出的周期为 P = 628.96 +/- 0.90 d，偏心率 e = 0.10 +/- 0.05，径向速度振幅 K = 142.1 +/- 7.2 m/s。演化轨迹产生的恒星质量为 1.13 +/- 0.11 M_sun，对应的最小伴星质量为 6.47 +/- 0.53 M_Jup，轨道半长轴为 a = 1.46 +/- 0.27 AU。去除伴星的轨道运动后，在径向速度数据中发现了约 520 d 的额外周期，但仅限于某些时间跨度。在 Halpha 和 Ca II 的等效宽度的变化中也发现了类似的周期。在谱线平分线测量中也发现了该周期三分之一的变化。 520 d周期被解释为恒星表面结构的旋转调制。然而，它的存在可能不会长久，并且仅出现在相隔 $\sim$ 10 年的径向速度数据的历元中。这可能是由于活动周期造成的。这里提供的数据提供了 Alpha Tau 行星伴星的进一步证据，以及与活动相关的径向速度变化。
We investigate the nature of the long-period radial velocity variations in Alpha Tau first reported over 20 years ago. We analyzed precise stellar radial velocity measurements for Alpha Tau spanning over 30 years. An examination of the Halpha and Ca II 8662 spectral lines, and Hipparcos photometry was also done to help discern the nature of the long-period radial velocity variations. Our radial velocity data show that the long-period, low amplitude radial velocity variations are long-lived and coherent. Furthermore, Halpha equivalent width measurements and Hipparcos photometry show no significant variations with this period. Another investigation of this star established that there was no variability in the spectral line shapes with the radial velocity period. An orbital solution results in a period of P = 628.96 +/- 0.90 d, eccentricity, e = 0.10 +/- 0.05, and a radial velocity amplitude, K = 142.1 +/- 7.2 m/s. Evolutionary tracks yield a stellar mass of 1.13 +/- 0.11 M_sun, which corresponds to a minimum companion mass of 6.47 +/- 0.53 M_Jup with an orbital semi-major axis of a = 1.46 +/- 0.27 AU. After removing the orbital motion of the companion, an additional period of ~ 520 d is found in the radial velocity data, but only in some time spans. A similar period is found in the variations in the equivalent width of Halpha and Ca II. Variations at one-third of this period are also found in the spectral line bisector measurements. The 520 d period is interpreted as the rotation modulation by stellar surface structure. Its presence, however, may not be long-lived, and it only appears in epochs of the radial velocity data separated by $\sim$ 10 years. This might be due to an activity cycle. The data presented here provide further evidence of a planetary companion to Alpha Tau, as well as activity-related radial velocity variations.