We present radial-velocity measurements for three solar-type stars (HD 127506, HD 174457 and HD 185414) hosting low-mass companions. The measurements were obtained with the ELODIE echelle spectrograph mounted on the 1.93–m telescope at Observatoire de Haute–Provence (CNRS, France) within the frame of the OHP-ELODIE Planet Search Programme. The inferred minimum masses of the detected companions are in the substellar mass range. Combining ELODIE radial-velocity data and HIPPARCOS astrometric data, the inclination angles of the orbital planes of HD 127506 and HD 174457 have been derived providing us with the de-projected masses of the companions: m2 = 44MJup for the companion of HD 127506 and m2= 0.13M⊙ for the companion of HD 174457. Moreover, using adaptive optics measurements, we show that HD 174457 is probably a (F8V + M7V + M3-4V) triple system. To date, only a minimal orbital solution is available for HD 185414.

We present a study of the Palomar Adaptive Optics System and the PHARO near infrared camera in coronagraphic mode. The camera provides two different focal plane occulting masks–opaque circular disks 0.43 and 0.97″ across. Three different pupil plane apodizing masks (Lyot masks) are also provided. The six different combinations of Lyot mask and focal plane mask suppress differently the point spread function of a bright star centered on the focal plane mask. We obtained images of the bright nearby star Gliese 614 with all six different configurations in the K filter. We measured the dynamic range achievable with these configurations. Within 2.5″, the dynamic range is at least 8 magnitudes at the 5σ level and as high as 12 in a 1 s exposure. This represents a substantial gain over similar techniques without adaptive optics.

Since the discovery of 51 Peg by Mayor & Queloz (1995) about 50 extra-solar planets have been discovered by means of the Doppler technique, and much more will follow. In future the goal will be to detect even lighter planets and/or planets with longer orbital periods, which may induce changes of only few m/s on the radial velocity of their parent star. Therefore very high performance instruments will be required. In view of the realization of HARPS (Pepe et al. 2000), the high-accuracy RV spectrograph for the ESO 3.6-m telescope dedicated to extra-solar planet search, we are investigating the accuracy limits and possible error sources. First results are presented in this paper.

We present radial-velocity data measurements for 4 solar-type stars (HD 6434, HD 19994, HD 92788 and HD 121504) harboring new detected planetary companions. The measurements were obtained with the CORALIE echelle spectrograph mounted on the 1.2–m “Leonard Euler” Swiss telescope at ESO–LaSilla Observatory (Chile). The minimum masses inferred for the planets are m2 sin i = 0.48, 2.0, 3.81 and 0.89MJup, respectively.

We investigate the prospects of detecting the presence of Na D absorption features during transits of the planet of HD209458 by means of high-resolution spectroscopy.

Schaefer, King & Deliyannis (2000) reported the discovery of powerful stellar flares on single, solar-type stars. The outbursts on these F8-G8 stars were 102–107 times more powerful than the largest solar flares. The observed properties are similar to the magnetic reconnection driven events of RS CVn binaries. Rubenstein & Schaefer (2000) suggested that superflares may be magnetic reconnection events mediated by the interaction between the magnetospheres of a close-in jovian planet and the star. Stars exhibiting superflares may therefore harbor detectable planets.

When a star with a mass of about 1 solar mass enters the red giant stage of its evolution, the radius of its atmosphere reaches several astronomical units. If the star possessed during its mainsequence life a planetary system, similar to the solar system, the planets will be embedded into a rather dense and hot medium. Effects of a planet revolving around a red giant at a short distance (inside its circumstellar envelope) are discussed. Systematic monitoring of the spectra of red giants may reveal periodicities in the emergence of shock-induced emission lines and thus to detect probable remnant planetary systems around these stars.

We present the spectroscopy results of a new set of planetary host stars discovered in the context of the Geneva extra-solar planet search programme. The analysis was based on high S/N spectra obtained with the CORALIE spectrograph at the 1.2-m Euler Swiss Telescope (at La Silla, ESO). We revisit the metallicity distribution of stars with planets. The present sample, largely enriched by the inclusion of the most recent discoveries, strongly suggests that stars with planets are anomalously metal rich, but that the source of the metallicity excess is most probably “primordial”.

In this contribution we present the results of the application of the bisector of the cross-correlation function as a diagnostic of activity-related radial-velocity variations. The results show that the technique is very effective. We present examples for which the application of the bisector analysis was essential to establish the planetary nature of the candidate or to exclude an orbital signature. An analysis of the behaviour of the bisector for active dwarfs of different spectral types shows that the relation between the bisector and the radial-velocity variation depends in a great extent on the v sin i of the star. The results may shed a new light on the intrinsic sources of radial-velocity variation for different types of solar-type dwarfs.

We present our radial-velocity data for HD 190228. The measurements were obtained with the ELODIE echelle spectrograph mounted on the 1.93-m telescope at Observatoire de Haute-Provence. A 1100-day periodic low-amplitude radial-velocity signal is detected revealing the presence of a planetary companion with a minimum mass of 5 MJup.

The methods used to calculate projected rotational velocities and effective temperatures for the targets observed during the 1998-1999 La Palma International Time campaign are described here. This is part of a project whose main goal is to perform a detailed chemical analysis of these objects and to study their potential implications in the planetary formation phenomenon.

We report preliminary results from a deep I-band optical search for substellar candidates in the p Oph star-forming region. The dusty molecular cloud provides an opaque screen at optical wavelengths, making the survey sensitive to faint substellar candidates near the cloud surface. Of the 89 objects detected in the oph A and oph C molecular cores, one third are substellar candidates.

IR spectroscopy with a resolution ⋋/△⋋ ≳ 10, 000 is a powerful technique for the investigation of short-periodic giant extra-solar planets. For an unambiguous direct detection attempt one exploits the large-amplitude Doppler modulation of the planet's IR spectrum. A successful measurement of the planet's radial velocity amplitude would yield directly the planet-star mass ratio. Spectral information can be extracted if high per-pixel S/N levels are achieved.

Based on the high-resolution, high signal-to-noise ratio spectra collected with the coudé echelle spectrograph attached to the 2.16m telescope at Beijing Astronomical Observatory, we determined the chemical abundance patterns for a sample of six planet-harboring stars. The result is used to investigate the connection between giant planet and high metallicity and to probe the influence of this process on other elements.

The discovery of gas giant planets around nearby stars has launched a new era in our understanding of the formation and evolution of planetary systems. However, none of the over four dozen companions detected to date strongly resembles Jupiter or Saturn: their inferred masses range from sub-Saturn-mass to 10 Jupiter-masses or more, while their orbits extend from periods of a few days to a few years. Given this situation, it seems prudent to re-examine mechanisms for gas giant planet formation. The two extreme cases are top-down or bottom-up. The latter is the core accretion mechanism, long favored for our Solar System, where a roughly 10 Earth-mass solid core forms by collisional accumulation of planetesimals, followed by hydrodynamic accretion of a gaseous envelope. The former is the long-discarded disk instability mechanism, where the protoplanetary disk forms self-gravitating, gaseous protoplanets through a gravitational instability of the gas, accompanied by settling and coagulation of dust grains to form solid cores. Both of these mechanisms have a number of advantages and disadvantages, making a purely theoretical choice between them difficult at present. Observations should be able to decide the dominant mechanism by dating the epoch of gas giant planet formation: core accretion requires more than a million years to form a Jupiter-mass planet, whereas disk instability is much more rapid.

We discuss theories of origin and evolution of the newly discovered extrasolar planetary systems. As these systems failed to fulfill prior expectations concerning their orbital structure, we are challenged to extend and/or revise many preexisting theories. Important extensions include migration of bodies in disks and planetary eccentricity pumping by planet-planet interaction and primordial disk-planet interaction. Progress in observational techniques will allow us to find which of these two types of interaction is responsible for the observed variety of orbits and masses of planets. New insights into the formation of giant planets in our system can be obtained by asking why Jupiter and Saturn are not larger, closer to the sun and/or do not follow noticeably elliptic orbits.

Accretion of terrestrial planets and solid cores of jovian planets is discussed, based on the results of our N-body simulations. Protoplanets accrete from planetesimals through runaway and oligarchic growth until they become isolated. The isolation mass of protoplanets in terrestrial planet region is about 0.2 Earth mass, which suggests that in the final stage of terrestrial planet formation giant impacts between the protoplanets occur. On the other hand, the isolation mass in jovian planet region is about a few to 10 Earth masses, which may be massive enough to form a gas giant. Extending the above arguments to disks with various initial masses, we discuss diversity of planetary systems. We predict that the extrasolar planets so far discovered may correspond to the systems formed from disks with large initial masses and that the other disks with smaller masses, which are the majority of the disks, may form Earth-like planets.

Low mass circumstellar disks are a result of the star formation process. The growth of dust and solid planets in such pre-planetary disks determines many properties of our solar system. Models of the Solar System giant planets indicate an enrichment of heavy elements and imply heavy element cores. Detailed models therefore describe giant planet formation as a consequence of the formation of solid planets that have grown sufficiently large to permanently bind gas from the protoplanetary nebula. The diversity of Solar System and extrasolar giant planets is explained by variations in the core growth rates caused by a coupling of the dynamics of planetesimals and the contraction of the massive envelopes they dive into, as well as by changes in the hydrodynamical accretion behavior of the envelopes resulting from differences in nebula density, temperature and orbital distance. Detailed formation models are able to determine observables as luminosities, radii and effective temperatures of young giant planets. Present observational techniques do now allow to probe star formation regions at ages covering all evolutionary stages of the giant planet formation process.

It is significant that the orbits of the planets in the solar system are very nearly circular, except for Mercury and Pluto where, conceivably, due to their comparatively small sizes, the tidal forces have played a less active role. Most of the suspected planets orbiting pulsars have nearly circular orbits. These systems tend to have minimum energy and are subjected to tidal forces. We find that a planet circularizes its orbit, in an effort to attain orbital stability and the ground state. Details can be found in Magalinsky & Chatterjee, 1997, and Magalinsky and Chatterjee, 2000.

We review our knowledge of the composition of cometary volatiles in the light of recent observations of comets C/1996 B2 (Hyakutake) and C/1995 01 (Hale-Bopp) and examine how this could constrain models of planetary system formation.