Monday, April 22, 2013

1304.5505 (A. -M. Lagrange et al.)

Planets around stars in young nearby associations *** radial Velocity searches: a feasibility study, and first results    [PDF]

A. -M. Lagrange, N. Meunier, G. Chauvin, M. Sterzik, F. Galland, G. Lo Curto, J. Rameau, D. Sosnowska
Stars in young nearby associations are the only targets allowing giant planet searches at all separations in the near future, by coupling indirect techniques such as radial velocity and deep imaging. These stars are first priorities targets for the forthcoming planets imagers on 10-m class telescopes. Young stars rotate more rapidly and are more active than their older counterparts. Both effects can limit the capability to detect planets using RV. We wish to explore the planet detection capabilities of a representative sample of stars in close and young associations with radial velocity data and explore the complementarity between this technique and direct imaging. We observed 26 such targets with spectral types from A to K and ages from 8 to 300 Myr with HARPS. We compute the detection limits. We also attempt to improve the detection limits in a few cases by correcting for the stellar activity. Our A-type stars RV show high frequency variations due to pulsations, while our F-K stars clearly show activity with more or less complex patterns. For F-K stars, the RV jitter and v sini rapidly decrease with star age. The data allow us to search for planets with periods typically ranging from 1 day to 100 days, and up to more than 500 days in a few cases. Within the present detection limits, no planet was found in our sample. For the bulk of our F-K stars, the detection limits fall down to sub-Jupiter masses.We show that these limits can be significantly improved by correcting even partially for stellar activity, down to a few Neptune masses for the least active stars. The detection limits on A-type stars can be significantly improved, down to a few Jupiter mass planets, provided an appropriate observing strategy. We finally show the tremendous potential of coupling RV and AO deep imaging results.
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