7 Summary

1.

We present more than 5 years of high precision differential radial velocities of 37 stars in the southern hemisphere observed with the 1.4 m CAT telescope and the CES spectrograph in Long Camera configuration.

2.

In this sample of stars we detected 1 extrasolar planet around the young and active G-dwarf $\iota$ Hor. The results for $\epsilon$ Eri contribute to the evidence for a long-period planetary companion.

3.

$\kappa$ For, HR 2400 and HR 3677 were found to be spectroscopic binaries with orbital periods significantly longer than the duration of the Long Camera survey. For all three stars the RV residuals after subtraction of the binary motion are consistent with our measurement errors.

4.

We identified low-amplitude linear RV trends for $\alpha$ For, HR 6416 and HR 8501 in agreement with their long-period binary orbtial motion. In the cases of $\beta$ Hyi and $\epsilon$ Ind we detected low-amplitude linear RV slopes of unknown origin.

5.

A period search within the complete RV data set did not reveal another significant periodic signal beside the planetary signal of $\iota$ Hor b and in the case of HR 8501 a signal with P>5000 days indicating the found linear RV trend for this star.

6.

We set quantitative upper mass-limits for planets orbiting the CES Long Camera survey stars based on our long-term RV data and numerical simulations of planetary signatures.

7.

Based on these mass-limits we can exclude the presence of short-period Jupiter-type planets around all examined survey stars, while planets with $m\sin i < 1~{M}_{\rm Jup}$ outside of 2 AU were undetectable by the CES Long Camera survey.

8.

Except for CES targets with B-V<0.6, a comparison of our simulation results with the RV-signals of known extrasolar planets shows that most of these planets could have been detected by the CES Long Camera survey.

9.

We demonstrate that the I₂-cell technique successfully compensates for the instrumental changes at the CES after April 1998 and that a smooth continuation of the CES planet search program is guaranteed. The increase in time baseline as well as a possible better RV precision with the Very Long Camera data will allow us to become sensitive to planetary systems more similar to our own Solar System.

Acknowledgements

We are thankful to the ESO OPC for generous allocation of observing time to the CES planet search program and to the ESO night assistants and support staff at La Silla and Garching (during remote observing runs). Our referee Stephane Udry had many important comments which helped to improve this article significantely. We would also like to thank Gustavo F. Porto de Mello, who contributed with many valuable discussions on the stellar properties of the CES target stars. ME and SE both acknowledge support by the ESO science office, ME was also supported by the Austrian Fond zur Förderung der wissenschaftlichen Forschung No. S7302 and SE under E.U. Marie Curie Fellowship contract HPMD-CT-2000-00005. ME, APH and WDC acknowledge support from NSF Grant AST-9808980 and NASA Grant NAG5-9227. During most of the time for this work MK was employed by the European Southern Observatory whose support is gratefully acknowledged. This work made us of the online SIMBAD database.