Hubble Space Telescope (HST ) observations of the nearby (3.22 pc), K2 V star ǫ Eridani have been combined with ground-based astrometric and radial velocity data to determine the mass of its known companion. We model the astrometric and radial velocity measurements simultaneously to obtain the parallax, proper motion, perturbation period, perturbation inclination, and perturbation size. Because of the long period of the companion, ǫ Eri b, we extend our astrometric coverage to a total of 14.94 years (including the three year span of the HST data) by including lower-precision ground-based astrometry from the Allegheny Multichannel Astrometric Photometer. Radial velocities now span 1980.8 -2006.3. We obtain a perturbation period, P = 6.85 ± 0.03 yr, semi-major axis α = 1.88 ± 0.20 mas, and inclination i = 30. • 1 ± 3. • 8. This inclination is consistent with a previously measured dust disk inclination, suggesting coplanarity. Assuming a primary mass M * = 0.83M ⊙ , we obtain a companion mass M = 1.55 ± 0.24 M Jup . Given the relatively young age of ǫ Eri (∼800 Myr), this accurate exoplanet mass and orbit can usefully inform future direct imaging attempts. We predict the next periastron at 2007.3 with a total separation, ρ = 0. ′′ 3 at position angle, p.a. = -27 • . Orbit orientation and geometry dictate that ǫ Eri b will appear brightest in reflected light very nearly at periastron. Radial velocities spanning over 25 years indicate an acceleration consistent with a Jupiter-mass object with a period in excess of 50 years, possibly responsible for one feature of the dust morphology, the inner cavity.

Abstract. We report results from 2 1/2 yr of high precision radial velocity (RV) monitoring of Barnard's star. The high RV measurement precision of the VLT-UT2+UVES of 2.65 m s −1 made the following findings possible.(1) The first detection of the change in the RV of a star caused by its space motion (RV secular acceleration). (2) An anti-correlation of the measured RV with the strength of the filling-in of the H α line by emission. (3) Very stringent mass upper limits to planetary companions. Using only data from the first 2 years, we obtain a best-fit value for the RV secular acceleration of 5.15 ± 0.89 m s −1 yr −1 . This agrees within 0.95σ with the predicted value of 4.50 m s −1 yr −1 based on the Hipparcos proper motion and parallax combined with the known absolute radial velocity of the star. When the RV data of the last half-year are added the best-fit slope is strongly reduced to 2.97 ± 0.51 m s −1 yr −1 (3.0σ away from the predicted value), clearly suggesting the presence of additional RV variability in the star. Part of it can be attributed to stellar activity as we demonstrate by correlating the residual RVs with an index that describes the filling-in of the H α line by emission. A correlation coefficient of −0.50 indicates that the appearance of active regions causes a blueshift of photospheric absorption lines. Assuming that active regions basically inhibit convection we discuss the possibility that the fundamental (inactive) convection pattern in this M4V star produces a convective redshift which would indicate that the majority of the absorption lines relevant for our RV measurements is formed in a region of convective overshoot. This interpretation could possibly extend a trend indicated in the behaviour of earlier spectral types that exhibit convective blueshift, but with decreasing line asymmetries and blueshifts as one goes from G to K dwarfs. Based on this assumption, we estimate that the variation of the visible plage coverage is about 20%. We also determine upper limits to the projected mass m sin i and to the true mass m of hypothetical planetary companions in circular orbits. For the separation range 0.017−0.98 AU we exclude any planet with m sin i > 0.12 M Jupiter and m > 0.86 M Jupiter . Throughout the habitable zone around Barnard's star, i.e. 0.034−0.082 AU, we exclude planets with m sin i > 7.5 M Earth and m > 3.1 M Neptune .

High-precision radial velocity (RV) measurements spanning the years 1980.8-2000.0 are presented for the nearby (3.22 pc) K2 V star e Eri. These data, which represent a combination of six independent data sets taken with four different telescopes, show convincing variations with a period of ≈7 yr. A least-squares orbital solution using robust estimation yields orbital parameters of period yr, velocity amplitude m s Ϫ1 , ec-P p 6.9K p 19 centricity , projected companion mass , and semimajor axis AU. Ca ii e p 0.6 M sin i p 0.86 M a p 3.4Jupiter 2 H and K S-index measurements spanning the same time interval show significant variations with periods of 3 and 20 yr yet none at the RV period. If magnetic activity were responsible for the RV variations, then it produces a significantly different period than is seen in the Ca ii data. Given the lack of Ca ii variation with the same period as that found in the RV measurements, the long-lived and coherent nature of these variations, and the high eccentricity of the implied orbit, Keplerian motion due to a planetary companion seems to be the most likely explanation for the observed RV variations. The wide angular separation of the planet from the star (approximately 1Љ) and the long orbital period make this planet a prime candidate for both direct imaging and space-based astrometric measurements.

Abstract. We present the complete results of the planet search program carried out at the ESO Coudé Echelle Spectrometer (CES) on La Silla, using the Long Camera from Nov. 1992 to April 1998. The CES survey has monitored 37 late-type (F8V -M5V) stars in the southern hemisphere for variations in their differential radial velocities (RV) in order to detect Doppler reflex motions caused by planetary companions. This led to the discovery of the first extrasolar planet in an Earth-like orbit around the young (ZAMS) and active G0V star ι Horologii . Here we present the RV results for all survey stars and perform a statistical examination of the whole data-set. Each star is tested for RV variability, RV trends (linear and non-linear) and significant periodic signals. β Hyi and Ind are identified as long-term, low-amplitude RV variables. Furthermore, for 30 CES survey stars we determine quantitative upper mass-limits for giant planets based on our long-term RV results. We find that the CES Long Camera survey would have detected short-period ("51 Peg-type") planets around all 30 stars but no planets with m sin i < 1 M Jup at orbital separations larger than 2 AU. Finally, we demonstrate that the CES planet search can be continued without applying velocity corrections to the RV results coming from the currently installed Very Long Camera at the CES.