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基于Kepler Q1--Q17数据对类太阳型恒星的行星生成率估算

Estimations of Planetary Occurrence Rates for Solar-type Stars with Data Release 25 from Kepler Q1--Q17 Observations

  • 摘要: 近30年来的系外行星探测揭示了行星在宇宙中普遍存在的事实. 为了深入研究适宜生命居住行星的普遍性, 一方面需要了解宜居行星的特性; 另一方面可以通过分析已发现系外行星的分布特征, 推算该类行星在恒星周围的存在几率. 在目前已发现的系外行星中, 凌星法发现的占据了绝大多数, 如Kepler空间望远镜所观测的系外行星共有2344颗. 2018年Kepler正式退役, 其科学团队发布了最终版的Kepler Data Release (DR25), 包含观测季度Q1--Q17的恒星共198709颗. 通过对Kepler数据的分析, 使用逆检测效率法和最大似然分析法两种不同的方法对系外行星半径周期参数空间内的行星生成率进行了估算, 同时将计算样本根据恒星的光谱类型进行分类, 分别估算得到了F、G、K型的Kepler恒星周围的行星生成率及其整体的生成率.对于半径范围1–20 R⊕(R⊕为一个地球半径), 轨道周期范围0.4–400 d的Kepler凌星系外行星, 宿主恒星为F型时逆检测效率法和最大似然法估算得到的行星生成率分别为0.36 ± 0.02和0.47 ± 0.02, 宿主恒星为G型时的行星生成率分别为1.62 ±0.05和1.23 ± 0.04, 宿主恒星为K型恒星时的行星生成率分别为2.61 ± 0.12和2.73 ± 0.13. 而逆检测效率法和最大似然法估算F、G、K型恒星周围存在这类行星的整体生成率分别为1.16 ± 0.03和0.90 ± 0.02. 最后, 对比分析了不同方法以及不同光谱型恒星间的行星生成率差异, 并结合前人研究讨论了该估算结果的可靠性.

     

    Abstract: The detection of exoplanets in the past three decades has revealed the fact that planets are ubiquitous in the universe. In order to deeply study the ubiquity of habitable planets, on one hand, we need to understand the characteristics of habitable planets; on the other hand, we can analyze the the distribution characteristics of exoplanets have been found, and the probability of occurrence of such planets around stars is calculated. Among the exoplanets that have been found so far, most of them are discovered by the transit method. For example, the number of the planets detected by the Kepler space telescope is 2344. Kepler telescope officially retired in 2018, and the Kepler team released the final version of Kepler Data Release (DR25), including a total of 198709 stars observed quarterly Q1--Q17. Here we analyze the Kepler data by using two different methods, Inverse Detection Efficiency Method (IDEM) and Maximum Likelihood Analysis (ML), to estimate planet occurrence rates in the space of the parameters of radius and orbital period. At the same time, the samples were classified according to the spectral types of stars, and the planet occurrence rates around F, G and K Kepler stars as well as its overall formation rate were estimated respectively. We estimate the planetary occurrence rates for planets among radius range of 1–20 R⊕ and orbital period range of 0.4–400 days by IDEM and ML, for which around F stars are 0.36±0.02 and 0.47±0.02. The rates around G stars by IDEM and ML are 1.62±0.05 and 1.23±0.04. The rates around K stars by IDEM and ML are 2.61 ± 0.12 and 2.73 ± 0.13. And the overall occurrence rate of such planets around F, G, K stars by IDEM and ML are 1.16 ± 0.03 and 0.90 ± 0.02. According to our estimation, we further show the results for the planet occurrence rates around stars with different spectral types by different methods, and discuss the reliability of the results in comparison with the previous studies.

     

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