EDP Sciences
Free access
Volume 407, Number 1, August III 2003
Page(s) 369 - 376
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20030843

A&A 407, 369-376 (2003)
DOI: 10.1051/0004-6361:20030843

Statistical properties of exoplanets

I. The period distribution: Constraints for the migration scenario
S. Udry, M. Mayor and N. C. Santos

Observatoire de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
(Received 4 November 2002 / Accepted 16 May 2003)

Interesting emerging observational properties of the period-mass distribution of extra-solar planets are discussed. New recent detections confirm the already emphasized lack of massive planets ( $m_2\sin{i}\ge 2\,M_{\rm Jup}$) on short-period orbits ( $P\le 100$ days). Furthermore, we point out i) a shortage of planets in the 10-100 day period range as well as ii) a lack of light planets ( $m_2\sin{i}\le 0.75\,M_{\rm Jup}$) on orbits with periods larger than ~100 days. The latter feature is shown not to be due to small-number statistics with Monte-Carlo simulations. These observational period-related characteristics are discussed in the context of the migration process of exoplanets. They are found to be in agreement with recent simulations of planet interactions with viscous disks. The observed valley at a few tens of days in the period distribution is interpreted as a transition region between two categories of planets that suffered different migration scenarios. The lack of light planets on longer-period orbits and the corresponding intriguing sharp limit in mass is tentatively explained by the runaway migration process recently studied by Masset & Papaloizou (2003). The observed properties also have implications for the observation strategies of the on-going surveys and of future higher-precision searches.

Key words: techniques: radial velocities -- stars: planetary systems

Offprint request: S. Udry, stephane.udry@obs.unige.ch

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