Characteristics of planetary candidates observed by Kepler. II. Analysis of the first four months of data

TLDR: In this article, the Kepler mission released data for 156,453 stars observed from the beginning of the science observations on 2009 May 2 through September 16, and there are 1235 planetary candidates with transit-like signatures detected in this period.

Abstract: On 2011 February 1 the Kepler mission released data for 156,453 stars observed from the beginning of the science observations on 2009 May 2 through September 16. There are 1235 planetary candidates with transit-like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class sizes: 68 candidates of approximately Earth-size (R_p < 1.25 R_⊕), 288 super-Earth-size (1.25 R_⊕ ≤ R_p < 2 R_⊕), 662 Neptune-size (2 R_⊕ ≤ R_p < 6 R_⊕), 165 Jupiter-size (6 R_⊕ ≤ R_p < 15 R_⊕), and 19 up to twice the size of Jupiter (15 R_⊕ ≤ R_p < 22 R_⊕). In the temperature range appropriate for the habitable zone, 54 candidates are found with sizes ranging from Earth-size to larger than that of Jupiter. Six are less than twice the size of the Earth. Over 74% of the planetary candidates are smaller than Neptune. The observed number versus size distribution of planetary candidates increases to a peak at two to three times the Earth-size and then declines inversely proportional to the area of the candidate. Our current best estimates of the intrinsic frequencies of planetary candidates, after correcting for geometric and sensitivity biases, are 5% for Earth-size candidates, 8% for super-Earth-size candidates, 18% for Neptune-size candidates, 2% for Jupiter-size candidates, and 0.1% for very large candidates; a total of 0.34 candidates per star. Multi-candidate, transiting systems are frequent; 17% of the host stars have multi-candidate systems, and 34% of all the candidates are part of multi-candidate systems.

Figures

Figure 15. Logarithm of the intrinsic frequencies as a function of stellar effective temperature after implementing the sensitivity corrections described in Section 4. The bins along the x-axis span 3000–4000 K, 4000–5000 K, 5000–6000 K, and 6000–7000 K, with each bin labeled by the central value.

Table 2 List of Planetary Candidates and Their Characteristics

Figure 16. Observed distributions of planetary candidates in multi-planet candidate systems. Bin sizes for the upper two panels and the lower panel are 2 days, 1 R⊕, and 1000 K, respectively. Refer to Table 6 for the definition of each size category.

Figure 1. Distributions of effective temperature and magnitude for the stars observed during Q2 and considered in this study. Bin size for the left panel is 500 K. The bin size for the right-hand panel is 1 mag from 6 to 9 and 0.25 mag from 9 to 16.5.

Figure 2. Size distribution of the number of Kepler candidates vs. planet radius (Rp) (upper panel). The logarithm of the number of candidates is presented in the lower panel to better show the tail of the distribution. Bin sizes in both panels are 1 R⊕.

Table 6 Number of Candidates vs. Size