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A Plateau in the Planet Population Below Twice the Size of Earth

Petigura, Erik A. and Marcy, Geoffrey W. and Howard, Andrew W. (2013) A Plateau in the Planet Population Below Twice the Size of Earth. Astrophysical Journal, 770 (1). Art. No. 69. ISSN 0004-637X.

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We carry out an independent search of Kepler photometry for small transiting planets with sizes 0.5-8.0 times that of Earth and orbital periods between 5 and 50 days, with the goal of measuring the fraction of stars harboring such planets. We use a new transit search algorithm, TERRA, optimized to detect small planets around photometrically quiet stars. We restrict our stellar sample to include the 12,000 stars having the lowest photometric noise in the Kepler survey, thereby maximizing the detectability of Earth-size planets. We report 129 planet candidates having radii less than 6 R_E found in three years of Kepler photometry (quarters 1-12). Forty-seven of these candidates are not in Batalha et al., which only analyzed photometry from quarters 1-6. We gather Keck HIRES spectra for the majority of these targets leading to precise stellar radii and hence precise planet radii. We make a detailed measurement of the completeness of our planet search. We inject synthetic dimmings from mock transiting planets into the actual Kepler photometry. We then analyze that injected photometry with our TERRA pipeline to assess our detection completeness for planets of different sizes and orbital periods. We compute the occurrence of planets as a function of planet radius and period, correcting for the detection completeness as well as the geometric probability of transit, R⋆/a. The resulting distribution of planet sizes exhibits a power law rise in occurrence from 5.7 R_E down to 2 R_E, as found in Howard et al. That rise clearly ends at 2 R_E . The occurrence of planets is consistent with constant from 2 R_E toward 1 R_E . This unexpected plateau in planet occurrence at 2 R_E suggests distinct planet formation processes for planets above and below 2 R_E . We find that 15.1^(+1.8)_(-2.7)% of solar type stars—roughly one in six—has a 1-2 R_E planet with P = 5-50 days.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Petigura, Erik A.0000-0003-0967-2893
Marcy, Geoffrey W.0000-0002-2909-0113
Howard, Andrew W.0000-0001-8638-0320
Additional Information:© 2013 The American Astronomical Society. Received 2013 February 9; accepted 2013 April 16; published 2013 May 24. The authors are indebted to Jon Jenkins, Peter Nugent, Howard Isaacson, Rea Kolbl, Eugene Chiang, Jason Rowe, and Stephen Bryson for productive and enlightening conversations that improved this work. We recognize the independent and complementary work of Fressin et al. (2013), who arrive at similar estimates of planet occurrence. We acknowledge salary support for Petigura by the National Science Foundation through the Graduate Research Fellowship Program. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under contract No. DE-AC02-05CH11231. This work made use of NASA's Astrophysics Data System Bibliographic Services as well as the NumPy (Oliphant 2007), SciPy (Jones et al. 2001), h5py (Collette 2008), IPython (Pérez & Granger 2007), and Matplotlib (Hunter 2007) Python modules. Finally, we extend special thanks to those of Hawai'ian ancestry on whose sacred mountain of Mauna Kea we are privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible.
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Department of Energy (DOE)DE-AC02-05CH11231
Subject Keywords:planetary systems – stars: statistics – techniques: photometric
Issue or Number:1
Record Number:CaltechAUTHORS:20170621-140413289
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Official Citation:Erik A. Petigura et al 2013 ApJ 770 69
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78423
Deposited By: Tony Diaz
Deposited On:21 Jun 2017 21:13
Last Modified:03 Oct 2019 18:08

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