The frequency of low-mass exoplanets. II. The 'period valley'

Wittenmyer, Robert A. and O'Toole, Simon J. and Jones, H. R. A. and Tinney, C. G. and Butler, R. P. and Carter, B. D. and Bailey, J. (2010) The frequency of low-mass exoplanets. II. The 'period valley'. The Astrophysical Journal, 722 (2). pp. 1854-1863. ISSN 0004-637X

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Abstract

Radial-velocity planet search campaigns are now beginning to detect low-mass 'Super-Earth' planets, with minimum masses M sin ilsim 10 M ⊕. Using two independently developed methods, we have derived detection limits from nearly four years of the highest-precision data on 24 bright, stable stars from the Anglo-Australian Planet Search. Both methods are more conservative than a human analyzing an individual observed data set, as is demonstrated by the fact that both techniques would detect the radial-velocity signals announced as exoplanets for the 61 Vir system in 50% of trials. There are modest differences between the methods which can be recognized as arising from particular criteria that they adopt. What both processes deliver is a quantitative selection process such that one can use them to draw quantitative conclusions about planetary frequency and orbital parameter distribution from a given data set. Averaging over all 24 stars, in the period range P< 300 days and the eccentricity range 0.0 < e < 0.6, we could detect 99% of planets with velocity amplitudes Kgsim 7.1 m s-1. For the best stars in the sample, we are able to detect or exclude planets with Kgsim 3 m s-1, corresponding to minimum masses of 8 M ⊕ (P = 5 days) or 17 M ⊕ (P = 50 days). Our results indicate that the observed 'period valley', a lack of giant planets (M > 100 M ⊕) with periods between 10 and 100 days, is indeed real. However, for planets in the mass range 10-100 M ⊕, our results suggest that the deficit of such planets may be a result of selection effects.

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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. NASA ADS entry for this research paper: http://adsabs.harvard.edu/abs/2010ApJ...722.1854W
Faculty / Department / School:	Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited:	22 Feb 2011 12:12
Last Modified:	24 Mar 2017 03:05
Uncontrolled Keywords:	planetary systems; radial velocities
Fields of Research :	02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems 01 Mathematical Sciences > 0105 Mathematical Physics > 010599 Mathematical Physics not elsewhere classified 09 Engineering > 0906 Electrical and Electronic Engineering > 090609 Signal Processing
Socio-Economic Objective:	E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI:	10.1088/0004-637X/722/2/1854
URI:	http://eprints.usq.edu.au/id/eprint/18183

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