退休的A星和他们的同伴VI。次巨星24 Sextanis和HD200964周围的一对相互作用的系外行星对
Retired A Stars and Their Companions VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD200964
摘要：
我们报告了G型次巨星24 Sextanis（= HD 90043）和HD 200964的径向速度测量结果。这两颗恒星都是大质量的演化恒星，由于一对类木行星的存在，它们呈现出周期性的变化。费尔伯恩天文台的T12 0.80米APT测光监测显示，这两颗恒星的亮度都是恒定的，<= 0.002等，从而加强了行星对径向速度变化的解释。24 Sex b和c的轨道周期分别为453.8天和883天，对应于半长轴1.333天文单位和2.08天文单位，最小质量（Msini）分别为1.99兆焦耳和0.86兆焦耳，假设恒星质量为1.54兆太阳。HD 200964 b和c的轨道周期分别为613.8天和825天，对应于半长轴1.601 AU和1.95 AU，最小质量分别为1.85 Mjup和0.90 Mjup，假设M* = 1.44 Msun。我们还进行了动力学模拟，以适当地解释行星之间的引力相互作用。大多数（如果不是全部的话）动力学稳定的解决方案包括交叉轨道，这表明每个系统都被锁定在平均运动共振中，防止近距离相遇并提供长期稳定性。24 Sex系统中的行星可能有接近2：1的周期比，而HD200964系统的周期比更紧密，接近4：3。然而，我们警告说，进一步的径向速度观测和更详细的动力学建模将需要提供明确的和独特的轨道解决方案，为这两种情况下，并确定这两个系统是否是真正的共振。
英文摘要：
We report radial velocity measurements of the G-type subgiants 24 Sextanis (=HD90043) and HD200964. Both are massive, evolved stars that exhibit periodic variations due to the presence of a pair of Jovian planets. Photometric monitoring with the T12 0.80m APT at Fairborn Observatory demonstrates both stars to be constant in brightness to <= 0.002 mag, thus strengthening the planetary interpretation of the radial velocity variations. 24 Sex b,c have orbital periods of 453.8 days and 883~days, corresponding to semimajor axes 1.333 AU and 2.08 AU, and minimum masses (Msini) 1.99 Mjup and 0.86 Mjup, assuming a stellar mass 1.54 Msun. HD200964 b,c have orbital periods of 613.8 days and 825 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and minimum masses 1.85 Mjup and 0.90 Mjup, assuming M* = 1.44 Msun. We also carry out dynamical simulations to properly account for gravitational interactions between the planets. Most, if not all, of the dynamically stable solutions include crossing orbits, suggesting that each system is locked in a mean motion resonance that prevents close encounters and provides long-term stability. The planets in the 24 Sex system likely have a period ratio near 2:1, while the HD200964 system is even more tightly packed with a period ratio close to 4:3. However, we caution that further radial velocity observations and more detailed dynamical modelling will be required to provide definitive and unique orbital solutions for both cases, and to determine whether the two systems are truly resonant.
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