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The Exoplanet Mass-Ratio Function From the MOA-II Survey: Discovery of a Break and Likely Peak at a Neptune MassWe report the results of the statistical analysis of planetary signals discovered in MOA-II microlensing survey alert system events from 2007 to 2012. We determine the survey sensitivity as a function of planet star mass ratio, q, and projected planet star separation, s, in Einstein radius units. We find that the mass-ratio function is not a single power law, but has a change in slope at q approx.10(exp -4), corresponding to approx. 20 Stellar Mass for the median host-star mass of approx. 0.6 M. We find significant planetary signals in 23 of the 1474 alert events that are well-characterized by the MOA-II survey data alone. Data from other groups are used only to characterize planetary signals that have been identified in the MOA data alone. The distribution of mass ratios and separations of the planets found in our sample are well fit by a broken power-law model. We also combine this analysis with the previous analyses of Gould et al. and Cassan et al., bringing the total sample to 30 planets. The unbroken power-law model is disfavored with a p-value of 0.0022, which corresponds to a Bayes factor of 27 favoring the broken power-law model. These results imply that cold Neptunes are likely to be the most common type of planets beyond the snow line.
Document ID
20170003331
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Suzuki, D.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Bennett, D. P.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Sumi, T.
(Osaka Univ. Osaka, Japan)
Bond, I. A.
(Massey University Auckland Auckland, New Zealand)
Rogers, L. A.
(Chicago Univ. Chicago, IL, United States)
Abe, F.
(Nagoya Univ. Nagoya, Japan)
Asakura, Y.
(Nagoya Univ. Nagoya, Japan)
Bhattacharya, A.
(Notre Dame Univ. Notre Dame, IN, United States)
Donachie, M.
(Auckland Univ. New Zealand)
Freeman, M.
(Auckland Univ. New Zealand)
Fukui, A.
(National Astronomical Observatory Okayama, Japan)
Hirao, Y.
(Osaka Univ. Osaka, Japan)
Itow, Y.
(Nagoya Univ. Nagoya, Japan)
Koshimoto, N.
(Osaka Univ. Osaka, Japan)
Li, M. C. A.
(Auckland Univ. New Zealand)
Ling, C. H.
(Massey University Auckland Auckland, New Zealand)
Masuda, K.
(Nagoya Univ. Nagoya, Japan)
Matsubara, Y.
(Nagoya Univ. Nagoya, Japan)
Muraki, Y.
(Nagoya Univ. Nagoya, Japan)
Nagakane, M.
(Osaka Univ. Osaka, Japan)
Onishi, K.
(Nagano National Coll. of Technology Nagano, Japan)
Oyokawa, H.
(Nagoya Univ. Nagoya, Japan)
Rattenbury, N.
(Auckland Univ. New Zealand)
Saito, To.
(Tokyo Metropolitan Coll. of Industrial Technology Tokyo, Japan)
Sharan, A.
(Auckland Univ. New Zealand)
Date Acquired
April 11, 2017
Publication Date
December 13, 2016
Publication Information
Publication: The Astrophysical Journal
Publisher: The American Astronomical Society
Volume: 833
Issue: 2
ISSN: 0004-637X
e-ISSN: 1538-4357
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN41544
Funding Number(s)
CONTRACT_GRANT: NNG17PT01A
CONTRACT_GRANT: NNX14AG49G
CONTRACT_GRANT: NNX13AF64G
CONTRACT_GRANT: NNX15AJ76G
Distribution Limits
Public
Copyright
Other
Keywords
MOA-II microlensing survey alert

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