Planet occurrence within 0.25AU of solar-type stars from Kepler
Name
Seager_Planet occurence.pdf
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1.33 MB
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Adobe PDF
Checksum (MD5)
01f70165616c99567f326d37502d141d
Author(s)
Seager, Sara
Rogers, Leslie Anne
Date Issued
June 2012
Journal
Astrophysical Journal. Supplement Series
Publisher
IOP Publishing
Citation
Howard, Andrew W. et al. “Planet occurrence within 0.25AU of solar-type stars from Kepler.” The Astrophysical Journal Supplement Series 201.2 (2012): 15. © 2012 IOP Publishing
Version
Final published version
Abstract
We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These results are based on the 1235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 R [subscript ⊕]. For each of the 156,000 target stars, we assess the detectability of planets as a function of planet radius, R [subscript p], and orbital period, P, using a measure of the detection efficiency for each star. We also correct for the geometric probability of transit, R ★/a. We consider first Kepler target stars within the "solar subset" having T [subscript eff] = 4100-6100 K, log g = 4.0-4.9, and Kepler magnitude Kp < 15 mag, i.e., bright, main-sequence GK stars. We include only those stars having photometric noise low enough to permit detection of planets down to 2 R [subscript ⊕]. We count planets in small domains of R [subscript p] and P and divide by the included target stars to calculate planet occurrence in each domain. The resulting occurrence of planets varies by more than three orders of magnitude in the radius-orbital period plane and increases substantially down to the smallest radius (2 R [subscript ⊕]) and out to the longest orbital period (50 days, ~0.25 AU) in our study. For P < 50 days, the distribution of planet radii is given by a power law, df/dlog R = k[subscript R]R [superscript α] with k[subscript R] = 2.9[superscript +0.5] [subscript – 0.4], α = –1.92 ± 0.11, and R ≡ R [subscript p]/R ⊕. This rapid increase in planet occurrence with decreasing planet size agrees with the prediction of core-accretion formation but disagrees with population synthesis models that predict a desert at super-Earth and Neptune sizes for close-in orbits. Planets with orbital periods shorter than 2 days are extremely rare; for R p > 2 R [subscript ⊕] we measure an occurrence of less than 0.001 planets per star. For all planets with orbital periods less than 50 days, we measure occurrence of 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2-4, 4-8, and 8-32 R [subscript ⊕], in agreement with Doppler surveys. We fit occurrence as a function of P to a power-law model with an exponential cutoff below a critical period P [subscript 0]. For smaller planets, P [subscript 0] has larger values, suggesting that the "parking distance" for migrating planets moves outward with decreasing planet size. We also measured planet occurrence over a broader stellar T [subscript eff] range of 3600-7100 K, spanning M0 to F2 dwarfs. Over this range, the occurrence of 2-4 R [subscript ⊕] planets in the Kepler field increases with decreasing T [subscript eff], with these small planets being seven times more abundant around cool stars (3600-4100 K) than the hottest stars in our sample (6600-7100 K).
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology. Department of Physics
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1088/0067-0049/201/2/15
