文章基本信息

标题：The Radial Velocity Variability of the K-giant γ Draconis: Stellar Variability Masquerading as a Planet
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作者：A. P. Hatzes ; M. Endl ; W. D. Cochran 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：155
期号：3
页码：1-11
DOI：10.3847/1538-3881/aaa8e1
语种：English
出版社：American Institute of Physics
摘要：We present precise stellar radial velocity (RV) measurements of γDra taken from 2003 to 2017. The data from 2003 to 2011 show coherent, long-lived variations with a period of 702 days. These variations are consistent with the presence of a planetary companion having msini=10.7 MJup whose orbital properties are typical for giant planets found around evolved stars. An analysis of the Hipparcos photometry, Ca II S-index measurements, and measurements of the spectral line shapes during this time show no variations with the RV of the planet, which seems to “confirm” the presence of the planet. However, RV measurements taken from 2011–2017 seem to refute this. From 2011–2013, the RV variations virtually disappear, only to return in 2014 but with a noticeable phase shift. The total RV variations are consistent either with amplitude variations on timescales of ≈10.6 year, or the beating effect between two periods of 666 and 801 days. It seems unlikely that both these signals stem from a twoplanet system. A simple dynamical analysis indicates that there is only a 1%–2% chance that the two-planet system is stable. Rather, we suggest that this multi-periodic behavior may represent a new form of stellar variability, possibly related to oscillatory convective modes. If such intrinsic stellar variability is common around K giant stars and is attributed to planetary companions, then the planet occurrence rate among these stars may be significantly lower than thought.
关键词：planetary systems;stars: individual (γ Dra);stars: oscillations;stars: variables: general;techniques: radial velocities