We analyse the properties of extrasolar planets, other close companions and their hosts. We start by identifying a sample of the detected extrasolar planets that is minimally affected by the selection effects of the Doppler detection method. With a simple analysis we quantify trends in the surface density of this sample in the Msini-period plane. A modest extrapolation of these trends puts Jupiter in the most densely occupied region of this parameter space, thus suggesting that Jupiter is a typical massive planet rather than an outlier. We then examine what fraction of Sun-like (~ FGK) stars have planets. We find that at least ~25% of stars possess planets when we limit our analysis to stars that have been monitored the longest and whose low surface activity allow the most precise radial velocity measurements. The true fraction of stars with planets may be as large as ~100%. We construct a sample of nearby Sun-like stars with close companions (period < 5 years). By using the same sample to extract the relative numbers of stellar, brown dwarf and planetary companions, we verify the existence of a very dry brown dwarf desert and describe it quantitatively. Approximately 16% of Sun-like stars have close companions more massive than Jupiter: 11% +- 3% are stellar, <1% are brown dwarf and 5% +- 2% are giant planets. A comparison with the initial mass function of individual stars and free-floating brown dwarfs, suggests either a different spectrum of gravitational fragmentation in the formation environment or post-formation migratory processes disinclined to leave brown dwarfs in close orbits. Finally we examine the relationship between the frequency of close companions and the metallicity of their Sun-like hosts. We confirm and quantify a ~4 sigma positive correlation between host metallicity and planetary companions. In contrast we find a ~2 sigma anti-correlation between host metallicity and the presence of a stellar companion. Upon dividing our sample into FG and K sub-samples, we find a negligible anti-correlation in the FG sub-sample and a ~3 sigma anti-correlation in the K sub-sample. A kinematic analysis suggests that this anti-correlation is produced by a combination of low-metallicity, high-binarity thick disk stars and higher-metallicity, lower-binarity thin disk stars.
| Identifer | oai:union.ndltd.org:ADTP/215549 |
| Date | January 2006 |
| Creators | Grether, Daniel Andrew, Physics, Faculty of Science, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Physics |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Daniel Andrew Grether, http://unsworks.unsw.edu.au/copyright |
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