Planet occurrence within 0.25AU of solar-type stars from Kepler

Howard, Andrew W. and Marcy, Geoffrey W. and Bryson, Stephen T. and Jenkins, Jon M. and Rowe, Jason F. and Batalha, Natalie M. and Borucki, William J. and Koch, David G. and Dunham, Edward W. and Gautier, Thomas N. and Van Cleve, Jeffrey and Cochran, William D. and Latham, David W. and Lissauer, Jack J. and Torres, Guillermo and Brown, Timothy M. and Gilliland, Ronald L. and Buchhave, Lars A. and Caldwell, Douglas A. and Christensen-Dalsgaard, Jorgen and Ciardi, David and Fressin, Francois and Haas, Michael R. and Howell, Steve B. and Kjeldsen, Hans and Seager, Sara and Rogers, Leslie and Sasselov, Dimitar D. and Steffen, Jason H. and Basri, Gibor S. and Charbonneau, David and Christiansen, Jessie and Clarke, Bruce and Dupree, Andrea and Fabrycky, Daniel C. and Fischer, Debra A. and Ford, Eric B. and Fortney, Jonathan J. and Tarter, Jill and Girouard, Forrest R. and Holman, Matthew J. and Johnson, John Asher and Klaus, Todd C. and MacHalek, Pavel and Moorhead, Althea V. and Morehead, Robert C. and Ragozzine, Darin and Tenenbaum, Peter and Twicken, Joseph D. and Quinn, Samuel N. and Isaacson, Howard and Shporer, Avi and Lucas, Philip W. and Walkowicz, Lucianne M. and Welsh, William F. and Boss, Alan and DeVore, Edna and Gould, Alan and Smith, Jeffrey C. and Morris, Robert L. and Prsa, Andrej and Morton, Timothy D. and Still, Martin and Thompson, Susan E. and Mullally, Fergal and Endl, Michael and MacQueen, Phillip J. (2012) Planet occurrence within 0.25AU of solar-type stars from Kepler. Astrophysical Journal, Supplement Series, 201 (2). pp. 15-34. ISSN 0067-0049

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We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50days 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 ⊕. For each of the 156,000 target stars, we assess the detectability of planets as a function of planet radius, R 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 consid'r first Kepler target stars within the 'solar subset' having T eff = 4100-6100K, 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 ⊕. We count planets in small domains of R 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 ⊕) and out to the longest orbital period (50days, 0.25AU) in our study. For P < 50 days, the distribution of planet radii is given by a power law, df/dlog R = kRR α with kR = 2.9+0.5 - 0.4, α = -1.92 ± 0.11, and R ≡ R 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 2days are extremely rare; for R p > 2 R ⊕ we measure an occurrence of less than 0.001 planets per star. For all planets with orbital periods less than 50days, 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 ⊕, 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 0. For smaller planets, P 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 eff range of 3600-7100K, spanning M0 to F2 dwarfs. Over this range, the occurrence of 2-4 R ⊕ planets in the Kepler field increases with decreasing T eff, with these small planets being seven times more abundant around cool stars (3600-4100K) than the hottest stars in our sample (6600-7100K).

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Access to published version in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 16 Jun 2017 06:43
Last Modified: 27 Jun 2017 04:50
Uncontrolled Keywords: planetary systems; stars; photometric;
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
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