Two Jovian Planets around the Giant Star HD 202696: A Growing Population of Packed Massive Planetary Pairs around Massive Stars?
Two Jovian Planets around the Giant Star HD 202696: A Growing Population of Packed Massive Planetary Pairs around Massive Stars?
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DOI：
10.3847/1538-3881/aafa11
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发表时间：
2019-01
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通讯作者：
T. Trifonov;S. Stock;T. Henning;S. Reffert;M. Kuerster;M. Lee;B. Bitsch;R. P. Butler;S. Vogt-S.-V
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作者：
T. Trifonov;S. Stock;T. Henning;S. Reffert;M. Kuerster;M. Lee;B. Bitsch;R. P. Butler;S. Vogt-S.-V
我们提出了围绕巨星HD 202696(=HIP 105056，BD+264118)存在新的双行星系统的证据。这一发现是基于2007年7月至2014年9月在凯克天文台进行的公共雇员径向速度(RV)测量。我们估计其恒星质量为HD 202696，它位于红巨星分支底部附近。RV数据的两行星自洽动力学模拟MCMC格式和长期稳定性检验表明，行星轨道周期分别为Pc=和Pc=天，偏心率Eb=和Ec=，以及最小动力学质量mb=和mc=MJup。我们稳定的MCMC样品与轨道构型是一致的，主要是在11：6的平均周期比及其附近的具有低偏心率的高阶平均运动公度。对于大多数稳定组态，我们发现了对齐或反对齐的近端振动(即，Δω在0°或180°附近摆动)，这表明HD 202696系统可能在高阶11：6平均运动共振附近受到长期扰动的主导。HD 202696系统是围绕一颗中等质量恒星的另一个木星质量对，其周期比低于2：1的平均运动共振。因此，HD 202696系统是一项重要的发现，它可能会揭示巨行星打破强烈的2：1平均运动共振并定居在更紧凑的轨道上所需的原始盘行星性质。
We present evidence for a new two-planet system around the giant star HD 202696 (=HIP 105056, BD +26 4118). The discovery is based on public HIRES radial velocity (RV) measurements taken at Keck Observatory between 2007 July and 2014 September. We estimate a stellar mass of for HD 202696, which is located close to the base of the red giant branch. A two-planet self-consistent dynamical modeling MCMC scheme of the RV data followed by a long-term stability test suggests planetary orbital periods of Pb = and Pc = days, eccentricities of eb = and ec = , and minimum dynamical masses of mb = and mc = MJup, respectively. Our stable MCMC samples are consistent with orbital configurations predominantly in a mean period ratio of 11:6 and its close-by high-order mean-motion commensurabilities with low eccentricities. For the majority of the stable configurations, we find an aligned or anti-aligned apsidal libration (i.e., Δω librating around 0° or 180°), suggesting that the HD 202696 system is likely dominated by secular perturbations near the high-order 11:6 mean-motion resonance. The HD 202696 system is yet another Jovian-mass pair around an intermediate-mass star with a period ratio below the 2:1 mean-motion resonance. Therefore, the HD 202696 system is an important discovery that may shed light on the primordial disk–planet properties needed for giant planets to break the strong 2:1 mean-motion resonance and settle in more compact orbits.