EXPRESS和PPPS观测到的低光度巨星周围的四颗类木行星
Four Jovian planets around low-luminosity giant stars observed by the EXPRESS and PPPS
摘要：
我们发现了围绕四颗低光度巨星运行的行星伴星，它们的M $_\star$在1.04和1.39 M之间，$_\odot$。所有四颗恒星都被EXoPlanets aRound Evolved StarS（EXPRESS）计划和泛太平洋行星搜索（PPPS）独立观测到。伴随信号是由近十年来获得的多历元精密径向速度揭示的。行星伴星的轨道周期在$\sim$ 1.2年和7.1年之间，最小质量为m $_{\rm p}$ sini $\sim$ 1.8-3.7 M $_{jup}$，偏心率在0.08和0.42之间。包括这四个新系统，我们已经发现了37颗巨星中的11颗的行星伴侣，这些巨星是EXPRESS和PPPS之间的共同目标。在从共同样本中排除了四个紧凑型双星之后，我们获得了一小部分距其母星$f = 33.3^{+9.0}_{-7.1} \%$ 5天文单位以内的巨行星（m $_{\rm p} \gtrsim$ 1-2 M $\_{jup}$）。这个分数是显着高于以前在文献中报道的不同径向速度调查。类似地，行星形成模型预测了比太阳质量更大的恒星周围气体巨星的比例。
英文摘要：
We report the discovery of planetary companions orbiting four low-luminosity giant stars with M$_\star$ between 1.04 and 1.39 M$_\odot$. All four host stars have been independently observed by the EXoPlanets aRound Evolved StarS (EXPRESS) program and the Pan-Pacific Planet Search (PPPS). The companion signals were revealed by multi-epoch precision radial velocities obtained during nearly a decade. The planetary companions exhibit orbital periods between $\sim$ 1.2 and 7.1 years, minimum masses of m$_{\rm p}$sini $\sim$ 1.8-3.7 M$_{jup}$ and eccentricities between 0.08 and 0.42. Including these four new systems, we have detected planetary companions to 11 out of the 37 giant stars that are common targets between the EXPRESS and PPPS. After excluding four compact binaries from the common sample, we obtained a fraction of giant planets (m$_{\rm p} \gtrsim$ 1-2 M$\_{jup}$) orbiting within 5 AU from their parent star of $f = 33.3^{+9.0}_{-7.1} \%$. This fraction is significantly higher than that previously reported in the literature by different radial velocity surveys. Similarly, planet formation models under predict the fraction of gas giant around stars more massive than the Sun.
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