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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 606305.0, MPI für Astronomie / Publikationen_mpia
High-contrast imaging search for planets and brown dwarfs around the most massive stars in the solar neighborhood
Authors:Janson, M.; Bonavita, M.; Klahr, H.; Lafrenière, D.; Jayawardhana, R.; Zinnecker, H.
Date of Publication (YYYY-MM-DD):2011
Journal Abbrev.:The Astrophysical Journal
Issue / Number:2
Audience:Not Specified
Abstract / Description:There has been a long-standing discussion in the literature as to whether core accretion or disk instability is the dominant mode of planet formation. Over the last decade, several lines of evidence have been presented showing that core accretion is most likely the dominant mechanism for the close-in population of planets probed by radial velocity and transits. However, this does not by itself prove that core accretion is the dominant mode for the total planet population, since disk instability might conceivably produce and retain large numbers of planets in the far-out regions of the disk. If this is a relevant scenario, then the outer massive disks of B-stars should be among the best places for massive planets and brown dwarfs to form and reside. In this study, we present high-contrast imaging of 18 nearby massive stars of which 15 are in the B2-A0 spectral-type range and provide excellent sensitivity to wide companions. By comparing our sensitivities to model predictions of disk instability based on physical criteria for fragmentation and cooling, and using Monte Carlo simulations for orbital distributions, we find that ~85% of such companions should have been detected in our images on average. Given this high degree of completeness, stringent statistical limits can be set from the null-detection result, even with the limited sample size. We find that <30% of massive stars form and retain disk instability planets, brown dwarfs, and very low mass stars of <100 M jup within 300 AU, at 99% confidence. These results, combined with previous findings in the literature, lead to the conclusion that core accretion is likely the dominant mode of planet formation. Based on data from the Gemini North telescope under programs
Free Keywords:brown dwarfs; planetary systems; stars: massive
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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