The frequency of low-mass exoplanets III: toward theta at short periods

Wittenmyer, Robert A. and Tinney, C. G. and Butler, R. P. and O'Toole, Simon J. and Jones, H. R. A. and Carter, B. D. and Bailey, J. and Horner, J. (2011) The frequency of low-mass exoplanets III: toward theta at short periods. The Astrophysical Journal, 738 (1). 81(1)-81(6). ISSN 0004-637X

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Determining the occurrence rate of 'super-Earth' planets (m sin i < 10 M⊕) is a critically important step on the path toward determining the frequency of Earth-like planets (η⊕), and hence the uniqueness of our solar system. Current radial-velocity surveys, achieving precisions of 1 m s–1, are now able to detect super-Earths and provide meaningful estimates of their occurrence rate. We present an analysis of 67 solar-type stars from the Anglo-Australian Planet Search specifically targeted for very high precision observations. When corrected for incompleteness, we find that the planet occurrence rate increases sharply with decreasing planetary mass. Our results are consistent with those from other surveys: in periods shorter than 50 days, we find that 3.0% of stars host a giant (msin i > 100 M ⊕) planet, and that 17.4% of stars host a planet with msin i < 10 M ⊕. The preponderance of low-mass planets in short-period orbits is in conflict with formation simulations in which the majority of super-Earths reside at larger orbital distances. This work gives a hint as to the size of η⊕, but to make meaningful predictions on the frequency of terrestrial planets in longer, potentially habitable orbits, low-mass terrestrial planet searches at periods of 100-200 days must be made an urgent priority for ground-based Doppler planet searches in the years ahead.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version made accessible, in accordance with the copyright policy of the publisher.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Mechanical and Mechatronic Engineering
Date Deposited: 24 Mar 2012 12:12
Last Modified: 24 Mar 2017 03:03
Uncontrolled Keywords: planetary systems; radial velocities
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
02 Physical Sciences > 0201 Astronomical and Space Sciences > 020108 Planetary Science (excl. Extraterrestrial Geology)
02 Physical Sciences > 0201 Astronomical and Space Sciences > 020101 Astrobiology
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1088/0004-637X/738/1/81

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