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| Paper: |
Doppler Detection of Extra-Solar Planets |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
9 |
| Authors: |
Marcy, G. W.; Butler, R. Paul |
| Abstract: |
The Doppler shifts of ~300 FGKM dwarfs have been monitored at a precision of ~10 m s^{-1} during ~10 yr . The rms Doppler variations are typically less than ~20 m s^{-1} and approach 3 m s^{-1} for slow rotators. However, eight stars exhibit velocity variations that stand above the norm, and are both periodic and Keplerian. These velocity variables imply the presence of companions that have masses (m sin i}) between 0.5 and 7 M_Jup and that orbit within 2.1 AU of the star. The detectability thresholds imply that ~6% of solar-type stars have giant planets within 3 AU . Surveys of ~600 stars made with lower Doppler precision show that ~2% of solar-type stars harbor more massive, ``brown dwarf'' companions within 5 AU (Mayor et al. 1997). The brown dwarf mass function is roughly flat from 70 to 10 M_Jup. But there is a tall spike in the mass function at the lowest masses, from 0 -- 10 M_Jup, that distinguishes them as a separate class, presumably planetary. Their small semi-major axes imply that they either formed in situ or suffered inward migration. Orbital migration of giant planets in pre-main-sequence appears inevitable, both theoretically and observationally. Time variability has been reported in the shape of one spectral line of 51 Peg. However, two other studies found no such line-shape variability in 51 Peg. Further, tau Bootis shows no line-profile variations, thus ruling out oscillations for it. Indeed, an orbiting planet explains all other observations of 51 Peg, including the single Doppler period that lacks overtones, the Doppler residuals to the Keplerian fit which are simply measurement errors, and the photometric stability (better than 1 millimag). A planetary companion remains the only physically plausible interpretation for it and for the long period Keplerian variables. |
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