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Techniques for Finding Close-in, Low-mass Planets around Evolved Intermediate-mass Stars

机译:在演化的中等质量恒星周围寻找近距离低质量行星的技术

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Jupiter-mass planets with large semimajor axes (a?>?1.0 au) occur at a higher rate around evolved intermediate-mass stars. There is a pronounced paucity of close-in (a P M planet M Jup ) planets, known as the "Planet Desert." Current radial velocity (RV) methods have yet to yield close-in, low-mass planets around these stars because the planetary signals could be hidden by the (5–10) m?s?1 RV variations caused by acoustic oscillations. We find that by implementing an observing strategy of taking three observations per night separated by an optimal Δt, which is a function of the oscillation periods and amplitudes, we can average over the stellar jitter and improve our sensitivity to low-mass planets. We find that Δt can be approximated using the stellar mass and radius given by the relationship Δt?=?1.79 . We test our proposed method by injecting planets into well-sampled data of a subgiant star, γ Cep. We compare the fraction of planets recovered by our method to the fraction of planets recovered using current RV observational strategies. We find that our method decreases the rms of the stellar jitter due to acoustic oscillations by a factor of three over current single epoch observing strategies used for subgiant stars. Our observing strategy provides a means to test whether the Planet Desert extends to lower-mass planets.
机译:具有大半长轴(a?>?1.0 au)的木星质量行星以较高的速率出现在演化的中质量恒星周围。近距离(P M行星M Jup)行星被称为“行星沙漠”,这是非常少见的。当前的径向速度(RV)方法尚未在这些恒星周围产生近距离的低质量行星,因为行星信号可能被声振荡引起的(5-10)m?s?1 RV变化所掩盖。我们发现,通过实施一种观测策略,每晚进行三个观测值,并以最佳Δt间隔,这是振荡周期和振幅的函数,可以对恒星抖动进行平均,并提高我们对低质量行星的敏感性。我们发现,Δt可以使用由关系式Δt1 =α1.79给出的恒星质量和半径来近似。我们通过将行星注入到亚恒星γCep的良好采样数据中来测试我们提出的方法。我们将通过我们的方法回收的行星比例与使用当前RV观测策略回收的行星比例进行比较。我们发现,在用于亚恒星的当前单历元观测策略中,我们的方法将由于声振荡而引起的恒星抖动的均方根降低了三倍。我们的观测策略提供了一种手段来测试“行星沙漠”是否扩展到低质量行星。

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