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arXiv · astro-ph/0109491

No planet for HD 166435

D. Queloz·G. W. Henry·J. P. Sivan·S. L. Baliunas·J. L. Beuzit·R. A. Donahue M. Mayor·D. Naef·C. Perrier·S. Udry
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Abstract

The G0V star HD166435 has been observed by the fiber-fed spectrograph ELODIE as one of the targets in the large extra-solar planet survey that we are conducting at the Observatory of Haute-Provence. We detected coherent, low-amplitude, radial-velocity variations with a period of 3.7987days, suggesting a possible close-in planetary companion. Subsequently, we initiated a series of high-precision photometric observations to search for possible planetary transits and an additional series of CaII H and K observations to measure the level of surface magnetic activity and to look for possible rotational modulation. Surprisingly, we found the star to be photometrically variable and magnetically active. A detailed study of the phase stability of the radial-velocity signal revealed that the radial-velocity variability remains coherent only for durations of about 30days. Analysis of the time variation of the spectroscopic line profiles using line bisectors revealed a correlation between radial velocity and line-bisector orientation. All of these observations, along with a one-quarter cycle phase shift between the photometric and the radial-velocity variationss, are well explained by the presence of dark photospheric spots on HD166435. We conclude that the radial-velocity variations are not due to gravitational interaction with an orbiting planet but, instead, originate from line-profile changes stemming from star spots on the surface of the star. The quasi-coherence of the radial-velocity signal over more than two years, which allowed a fair fit with a binary model, makes the stability of this star unusual among other active stars. It suggests a stable magnetic field orientation where spots are always generated at about the same location on the surface of the star.

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D. Queloz, G. W. Henry, J. P. Sivan, S. L. Baliunas, J. L. Beuzit, R. A. Donahue M. Mayor, D. Naef, C. Perrier, S. Udry. 2001-09-26. No planet for HD 166435. https://doi.org/10.1051/0004-6361%3A20011308

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