Abstract: We present exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening. In the limit that the planet radius is less than a tenth of the stellar radius, we show that the exact lightcurve can be well approximated by assuming the region of the star blocked by the planet has constant surface brightness. We apply these results to the HST observations of HD 209458, showing that the ratio of the planetary to stellar radii is 0.1207+-0.0003. These formulae give a fast and accurate means of computing lightcurves using limb-darkening coefficients from model atmospheres which should aid in the detection, simulation, and parameter fitting of planetary transits.

Abstract: The timescales and mechanisms for the formation and chemical differentiation of the planets can be quantified using the radioactive decay of short-lived isotopes. Of these, the (182)Hf-to-(182)W decay is ideally suited for dating core formation in planetary bodies. In an earlier study, the W isotope composition of the Earth's mantle was used to infer that core formation was late (> or = 60 million years after the beginning of the Solar System) and that accretion was a protracted process. The correct interpretation of Hf-W data depends, however, on accurate knowledge of the initial abundance of (182)Hf in the Solar System and the W isotope composition of chondritic meteorites. Here we report Hf-W data for carbonaceous and H chondrite meteorites that lead to timescales of accretion and core formation significantly different from those calculated previously. The revised ages for Vesta, Mars and Earth indicate rapid accretion, and show that the timescale for core formation decreases with decreasing size of the planet. We conclude that core formation in the terrestrial planets and the formation of the Moon must have occurred during the first approximately 30 million years of the life of the Solar System.

Abstract: Received 7 February 2002 / Accepted 19 March 2002 We present the discovery of two Saturn-mass companions to HD 108147 and HD 168746. Both belong to the lightest ever discovered planets. The minimum mass of the companion to HD 168746 is of only 0.77 the mass of Saturn and its orbital period is 6.4 days. The companion to HD 108147 orbits its parent star in 10.9 days and its minimum mass is 1.34 that of Saturn. Its orbit is characterized by a high eccentricity, e = 0.50, indicating possibly the presence of a second companion. The detection of Saturn-mass planets by means of the Doppler technique demands high radial-velocity measurement precision. The two new candidates were discovered by means of the CORALIE echelle spectrograph. The instrumental accuracy of CORALIE combined with the simultaneous ThAr-reference technique has reached a level better than 3 m s - 1 . On many observed objects the precision is now limited by photon noise. We present in this paper the weighted cross-correlation technique, which leads to an improvement in the photon noise of the computed radial velocity. We discuss as well a modification of the numerical cross-correlation mask which reduces significantly the residual perturbation effects produced by telluric absorption lines.

Abstract: The discovery by Marcy and coworkers of two planets in 2 : 1 orbital resonance about the star GJ 876 has been supplemented by a dynamical fit to the data by Laughlin & Chambers, which places the planets in coplanar orbits deep in three resonances at the 2 : 1 mean-motion commensurability. The selection of this almost singular state by the dynamical fit means that the resonances are almost certainly real, and with the small amplitudes of libration of the resonance variables, indefinitely stable. Several unusual properties of the 2 : 1 resonances are revealed by the GJ 876 system. The libration of both lowest order mean-motion resonance variables and the secular resonance variable, θ1 = λ1 - 2λ2 + 1, θ2 = λ1 - 2λ2 + 2, and θ3 = 1 - 2, about 0° (where λ1,2 are the mean longitudes of the inner and outer planet and 1,2 are the longitudes of periapse) differs from the familiar geometry of the Io-Europa pair, where θ2 and θ3 librate about 180°. By considering the condition that 1 = 2 for stable simultaneous librations of θ1 and θ2, we show that the GJ 876 geometry results from the large orbital eccentricities ei, whereas the very small eccentricities in the Io-Europa system lead to the latter's geometry. Surprisingly, the GJ 876 configuration, with θ1, θ2, and θ3 all librating, remains stable for e1 up to 0.86 and for amplitude of libration of θ1 approaching 45° with the current eccentricities—further supporting the indefinite stability of the existing system. Any process that drives originally widely separated orbits toward each other could result in capture into the observed resonances at the 2 : 1 commensurability. We find that forced inward migration of the outer planet of the GJ 876 system results in certain capture into the observed resonances if initially e1 0.06 and e2 0.03 and the migration rate |2/a2| 3 × 10-2(a2/AU)-3/2 yr-1. Larger eccentricities lead to likely capture into higher order resonances before the 2 : 1 commensurability is reached. The planets are sufficiently massive to open gaps in the nebular disk surrounding the young GJ 876 and to clear the disk material between them, and the resulting planet-nebular interaction typically forces the outer planet to migrate inward on the disk viscous timescale, whose inverse is about 3 orders of magnitude less than the above upper bound on |2/a2| for certain capture. If there is no eccentricity damping, eccentricity growth is rapid with continued migration within the resonance, with ei exceeding the observed values after a further reduction in the semimajor axes ai of only 7%. With eccentricity damping i/ei = -K|i/ai|, the eccentricities reach equilibrium values that remain constant for arbitrarily long migration within the resonances. The equilibrium eccentricities are close to the observed eccentricities for K ≈ 100 if there is migration and damping of the outer planet only, but for K ≈ 10 if there is also migration and damping of the inner planet. This result is independent of the magnitude or functional form of the migration rate i as long as i/ei = -K|i/ai|. Although existing analytic estimates of the effects of planet-nebula interaction are consistent with this form of eccentricity damping for certain disk parameter values, it is as yet unclear that such interaction can produce the large value of K required to obtain the observed eccentricities. The alternative eccentricity damping by tidal dissipation within the star or the planets is completely negligible, so the observed dynamical properties of the GJ 876 system may require an unlikely fine-tuning of the time of resonance capture to be near the end of the nebula lifetime.

Abstract: The major goals of NASA's Terrestrial Planet Finder (TPF) and the European Space Agency's Darwin missions are to detect terrestrial-sized extrasolar planets directly and to seek spectroscopic evidence of habitable conditions and life. Here we recommend wavelength ranges and spectral features for these missions. We assess known spectroscopic molecular band features of Earth, Venus, and Mars in the context of putative extrasolar analogs. The preferred wavelength ranges are 7-25 μm in the mid-IR and 0.5 to ~1.1 μm in the visible to near-IR. Detection of O2 or its photolytic product O3 merits highest priority. Liquid H2O is not a bioindicator, but it is considered essential to life. Substantial CO2 indicates an atmosphere and oxidation state typical of a terrestrial planet. Abundant CH4 might require a biological source, yet abundant CH4 also can arise from a crust and upper mantle more reduced than that of Earth. The range of characteristics of extrasolar rocky planets might far exceed that of the Solar Syst...

Abstract: We examine formation conditions for the Galilean satellites in the context of models of late-stage giant planet accretion and satellite-disk interactions. We first reevaluate the current standard, in which the satellites form from a ‘‘ minimum mass subnebula ’’ disk, obtained by augmenting the mass of the current satellites to solar abundance and resulting in a disk mass containing about 2% of Jupiter’s mass. Conditions in such a massive and gas-rich disk are difficult to reconcile with both the icy compositions of Ganymede and Callisto and the protracted formation time needed to explain Callisto’s apparent incomplete differentiation. In addition, we argue that disk torques in such a gas-rich disk would cause large satellites to be lost to inward decay onto the planet. These issues have prevented us from identifying a self-consistent scenario for the formation and survival of the Galilean satellites using the standard model. We then consider an alternative, in which the satellites form in a circumplanetary accretion disk produced during the very end stages of gas accretion onto Jupiter. In this case, an amount of gas and solids of at least � 0.02 Jovian masses must still be processed through the disk during the satellite formation era, but this amount need not have been present all at once. We find that an accretion disk produced by a slow inflow of gas and solids, e.g., 2 � 10 � 7 Jovian masses per year, is most consistent with conditions needed to form the Galilean satellites, including disk temperatures low enough for ices and protracted satellite accretion times of � 10 5 yr. Such a ‘‘ gas-starved ’’ disk has an orders-of-magnitude lower gas surface density than the minimum mass subnebula (and for many cases is optically thin). Solids delivered to the disk build up over many disk viscous cycles, resulting in a greatly reduced gas-to-solids ratio during the final stages of satellite accretion. This allows for the survival of Galilean-sized satellites against disk torques over a wide range of plausible conditions.

Abstract: The presence of planets around solar-type stars suggests that many white dwarfs should have relic planetary systems. While planets closer than ~5 AU will most likely not survive the post-main-sequence lifetime of their parent star, any planet with semimajor axis greater than 5 AU will survive, and its semimajor axis will increase as the central star loses mass. Since the stability of adjacent orbits to mutual planet-planet perturbations depends on the ratio of the planet mass to the central star's mass, some planets in previously stable orbits around a star undergoing mass loss will become unstable. We show that when mass loss is slow, systems of two planets that are marginally stable can become unstable to close encounters, while for three planets the timescale for close approaches decreases significantly with increasing mass ratio. These processes could explain the presence of anomalous IR excesses around white dwarfs that cannot be explained by close companions, such as G29-38, and may also be an important factor in explaining the existence of DAZ white dwarfs. The onset of instability through changing mass ratios will also be a significant effect for planetary embryos gaining mass in protoplanetary disks.

Abstract: Mantle Convection in the Earth and Planets is a comprehensive synthesis of all aspects of mantle convection within the Earth, the terrestrial planets, the Moon, and the Galilean satellites of Jupiter. Mantle convection sets the pace for the evolution of the Earth as a whole. It influences Earth’s topography, gravitational field, geodynamo, climate system, cycles of glaciation, biological evolution, and formation of mineral and hydrocarbon resources. It is the primarymechanism for the transport of heat from the Earth’s deep interior to its surface. Mantle convection is the fundamental cause of plate tectonics, formation and drift of continents, volcanism, earthquakes, and mountain building. This book provides both a connected overview and an in-depth analysis of the relationship between these phenomena and the process of mantle convection. Complex geodynamical processes are explained with simple mathematical models. The book includes up-to-date discussions of the latest research developments that have revolutionized our understanding of the Earth and the planets. These developments include:

Abstract: About one-quarter of the extrasolar giant planets discovered so far have orbital distances smaller than 0.1 AU. These "51 Peg b-like" planets can now be directly characterized, as shown by the planet transiting in front the star HD 209458. We review the processes that affect their evolution. We apply our work to the case of HD 209458b, whose radius has been recently measured. We argue that its radius can be reproduced only when the deep atmosphere is assumed to be unrealistically hot. When using more realistic atmospheric temperatures, an energy source appears to be missing in order to explain HD 209458b's large size. The most likely source of energy available is not in the planet's spin or orbit, but in the intense radiation received from the parent star. We show that the radius of HD 209458b can be reproduced if a small fraction (∼1%) of the stellar flux is transformed into kinetic energy in the planetary atmosphere and subsequently converted to thermal energy by dynamical processes at pressures of tens of bars.

Abstract: We propose that coronagraphic imaging in combination with moderate to high spectral resolution from the outset may prove more effective in both detecting extrasolar planets and characterizing them than a standard coronagraphic imaging approach. We envisage an integral-field spectrograph coupled to a coronagraph to produce a data cube of two space dimensions and one wavelength. For the idealized case where the spectrum of the star is well known and unchanging across the field, we discuss the utility of cross-correlation to seek the extrasolar planet signal and describe a mathematical approach to completely eliminate stray light from the host star (although not its Poisson noise). For the case where the point-spread function (PSF) is dominated by diffraction and scattering effects and comprises a multitude of speckles within an Airy pattern, typical of a space-based observation, we turn the wavelength dependence of the PSF to advantage and present a general way to eliminate the contribution from the star while preserving both the flux and spectrum of the extrasolar planet. We call this method spectral deconvolution. We illustrate the dramatic gains by showing an idealized simulation that results in a 20 ? detection of a Jovian planet at 2 pc with a 2 m coronagraphic space telescope, even though the planet's peak flux is only 1% that of the PSF wings of the host star. This scales to detection of a terrestrial extrasolar planet at 2 pc with an 8 m coronagraphic Terrestrial Planet Finder in ~7 hr (or less with appropriate spatial filtering). Data on the spectral characteristics of the extrasolar planet and hence on its atmospheric constituents and possible biomarkers are naturally obtained as part of this process.

Abstract: Transit photometry is a promising method for discovering extrasolar planets as small as Earth from spacebased photometers, and several near-term photometric missions are on the drawing board. In particular, NASA’s recently selected Kepler mission is devoted primarily to detecting extrasolar planets. The success of these e!o rts depends in part on the ability to detect transit signatures against the inherent photometric variability of the target stars. While other noise sources such as shot noise and CCD noise are under the control of the instrument designers, this one is not. The photometric variability of solar-like stars presents a fundamental lower limit to the minimum detectable planet radius for a given star and number of observed transits. In this paper we examine the capability of such missions using bolometric data for the only star for which su"cient photometric precision exists to address this question: the Sun. The results indicate that solar-like variability does not prevent the detection of Earth-sized planets even for stars rotating significantly faster than the Sun. Four transits are detectable for mv ! 12 stars with rotation periods as short as " 21 days, while six transitsallowdetectionforstellarrotation periods asshortas" 16days.Indeed, thelimitsposed bysolar-like variability allow for the detection of planets significantly smaller than Earth orbiting Sun-like stars. Planets as small as 0.6 Earth radii exhibitingat least sixtransits can be detected orbiting bright (mv ! 10) solar analogs. Subject headings: methods: data analysis — planetary systems — techniques: photometric

Abstract: About one-quarter of the extrasolar giant planets discovered so far have orbital distances smaller than 0.1 AU. These ``51Peg b-like'' planets can now be directly characterized, as shown by the planet transiting in front the star HD209458. We review the processes that affect their evolution. We apply our work to the case of HD209458b, whose radius has been recently measured. We argue that its radius can be reproduced only when the deep atmosphere is assumed to be unrealistically hot. When using more realistic atmospheric temperatures, an energy source appears to be missing in order to explain HD209458b's large size. The most likely source of energy available is not in the planet's spin or orbit, but in the intense radiation received from the parent star. We show that the radius of HD209458b can be reproduced if a small fraction (~1%) of the stellar flux is transformed into kinetic energy in the planetary atmosphere and subsequently converted to thermal energy by dynamical processes at pressures of tens of bars.

Abstract: The presence of planets around solar-type stars suggests that many white dwarfs should have relic planetary systems. While planets closer than $\sim$ 5~AU will most likely not survive the post-main sequence lifetime of its parent star, any planet with semimajor axis $>$ 5~AU will survive, and its semimajor axis will increase as the central star loses mass. Since the stability of adjacent orbits to mutual planet-planet perturbations depends on the ratio of the planet mass to the central star's mass, some planets in previously stable orbits around a star undergoing mass loss will become unstable. We show that when mass loss is slow, systems of two planets that are marginally stable can become unstable to close encounters, while for three planets the timescale for close approaches decreases significantly with increasing mass ratio. These processes could explain the presence of anomalous IR excesses around white dwarfs that cannot be explained by close companions, such as G29-38, and may also be an important factor in explaining the existence of DAZ white dwarfs. The onset of instability through changing mass-ratios will also be a significant effect for planetary embryos gaining mass in protoplanetary disks.

Abstract: This paper presents a model for the outcome of collisions between planetesimals in a debris disc, and assesses the impact of collisional processes on the structure and size distribution of the disc. The model is presented by its application to Fomalhaut’s collisionally replenished dust disc; a recent 450-µm image of this disc shows a clump embedded within it with a flux ∼5 per cent of the total. The following conclusions are drawn. (i) Spectral energy distribution modelling is consistent with Fomalhaut’s disc having a collisional cascade size distribution extending from bodies 0.2 m in diameter (the largest that contribute to the 850-µm flux) down to 7-µm-sized dust (smaller grains are blown out of the system by radiation pressure). (ii) Collisional lifetime arguments imply that the collisional cascade starts with planetesimals 1.5‐4 km in diameter, and so has a mass of 20‐30 M⊕. Any larger bodies must be predominantly primordial. (iii) Constraints on the time-scale for the ignition of the collisional cascade from planet formation models are consistent with these primordial planetesimals having the same distribution as the cascade extending up to 1000 km, resulting in a disc mass of 5‐10 times the minimum solar nebula mass. (iv) The debris disc is expected to be intrinsically clumpy, as planetesimal collisions result in dust clumps that can last up to 700 orbital periods. The intrinsic clumpiness of Fomalhaut’s disc is below current detection limits, but it could be detectable by future observatories such as ALMA, and could provide the only way of determining this primordial planetesimal population. Also, we note that such intrinsic clumpiness in an exozodiacal cloudlike disc could present a confusion limit when trying to detect terrestrial planets. (v) The observed clump could have originated in a collision between two runaway planetesimals, both larger than 1400 km in diameter. It appears unlikely that we should witness such an event unless both the formation of these runaways and the ignition of the collisional cascade occurred relatively recently (within the last ∼10 Myr), however this is a topic which would benefit from further exploration using planet formation and collisional models. (vi) Another explanation for Fomalhaut’s clump is that ∼5 per cent of the planetesimals in the ring were trapped in 1:2 resonance with a planet orbiting at 80 au when it migrated out as a result of the clearing of a residual planetesimal disc. The motion on the sky of such a clump would be 0.2 arcsec yr −1 ,

Abstract: In this article we present the case of HD 41004 AB, a system composed of a K0V star and a 3.7-mag fainter M-dwarf companion. We have obtained 86 CORALIE spectra of this system with the goal of obtaining precise radial-velocity measure- ments. Since HD 41004 A and B are separated by only 0.5 00 , in every spectrum taken for the radial-velocity measurement, we are observing the blended spectra of the two stars. An analysis of the measurements has revealed a velocity variation with an amplitude of about 50 m s 1 and a periodicity of 1.3 days. This radial-velocity signal is consistent with the expected variation induced by the presence of a companion to either HD 41004 A or HD 41004 B, or to some other eect due to e.g. activity related phenomena. In particular, such a small velocity amplitude could be the signature of the presence of a very low mass giant plane- tary companion to HD 41004 A, whose light dominates the spectra. The radial-velocity measurements were then complemented with a photometric campaign and with the analysis of the bisector of the CORALIE Cross-Correlation Function (CCF). While the former revealed no significant variations within the observational precision of0.003-0.004 mag (except for an observed flare event), the bisector analysis showed that the line profiles are varying in phase with the radial-velocity. This latter result, complemented with a series of simulations, has shown that we can explain the observations by considering that HD 41004 B has a brown-dwarf companion orbiting with the observed 1.3-day period. As the spectrum of the fainter HD 41004 B "moves" relative to the one of HD 41004 A (with an amplitude of a few km s 1 ), the relative position of the spectral lines of the two spectra changes, thus changing the blended line-profiles. This variation is large enough to explain the observed radial-velocity and bisector variations, and is compatible with the absence of any photometric signal. If confirmed, this detection represents the first discovery of a brown dwarf in a very short period (1.3-day) orbit around an M dwarf. Finally, this case should be taken as a serious warning about the importance of analyzing the bisector when looking for planets using radial-velocity techniques.

Abstract: Coronagraphic imaging in combination with moderate to high spectral resolution may prove more effective in both detecting extrasolar planets and characterizing them than a standard coronagraphic imaging approach. We envisage an integral-field spectrograph coupled to a coronagraph to produce a 3D datacube. For the idealised case where the spectrum of the star is well-known and unchanging across the field, we discuss the utility of cross-correlation to seek the extrasolar planet signal, and describe a mathematical approach to completely eliminate stray light from the host star (although not its Poisson noise). For the case where the PSF is dominated by diffraction and scattering effects, and comprises a multitude of speckles within an Airy pattern typical of a space-based observation, we turn the wavelength dependence of the PSF to advantage and present a general way to eliminate the contribution from the star while preserving both the flux and spectrum of the extrasolar planet. We call this method `spectral deconvolution'. We illustrate the dramatic gains by showing an idealized simulation that results in a 20-sigma detection of a Jovian planet at 2 pc with a 2-m coronagraphic space telescope, even though the planet's peak flux is only 1% that of the PSF wings of the host star. This scales to detection of a terrestrial extrasolar planet at 2 pc with an 8-m coronagraphic Terrestrial Planet Finder (TPF) in ~7 hr (or less with appropriate spatial filtering). Data on the spectral characteristics of the extrasolar planet and hence on its atmospheric constituents and possible biomarkers are obtained naturally as part of this process.

Abstract: We study the evolution of embedded protoplanets in a protostellar disk using very high resolution nested- grid computations This method allows us to perform global simulations of planets orbiting in disks and, at the same time, to resolve in detail the dynamics of the flow inside the Roche lobe of the planet The primary interest of this work lies in the analysis of the gravitational torque balance acting on the planet For this purpose we study planets of dierent masses, ranging from one Earth-mass up to one Jupiter-mass, assuming typical parameters of the protostellar disk The high resolution supplied by the nested-grid technique permits an evaluation of the torques, resulting from short and very short range disk-planet interactions, more reliable than the one previously estimated with the aid of numerical methods Likewise, the mass flow onto the planet is computed in a more accurate fashion The obtained migration time scales are in the range from few times 10 4 years, for intermediate mass planets, to 10 6 years, for very low and high mass planets These are longer than earlier assessments due to the action of circumplanetary material Typical growth time scales depend strongly on the planetary mass Below 64 Earth-masses, we nd this time scale to increase as the 2=3-power of the planet's mass; otherwise it rises as the 4=3-power In the case of Jupiter-size planets, the growth time scale is several times ten thousand years

Abstract: This paper presents a model for the outcome of collisions between planetesimals in a debris disk and assesses the impact of collisional processes on the structure and size distribution of the disk. The model is presented by its application to Fomalhaut's collisionally replenished dust disk; a recent 450 micron image of this disk shows a clump embedded within it with a flux ~5 per cent of the total. The following conclusions are drawn: (i) SED modelling is consistent with Fomalhaut's disk having a collisional cascade size distribution extending from bodies 0.2 m in diameter down to 7 micron-sized dust. (ii) Collisional lifetime arguments imply that the cascade starts with planetesimals 1.5-4 km in diameter. Any larger bodies must be predominantly primordial. (iii) Constraints on the timescale for the ignition of the cascade are consistent with these primordial planetesimals having a distribution that extends up to 1000km, resulting in a disk mass of 5-10 times the minimum mass solar nebula. (iv) The debris disk is expected to be intrinsically clumpy, since planetesimal collisions result in dust clumps. The intrinsic clumpiness of Fomalhaut's disk is below current detection limits, but could be detectable by future observatories such as the ALMA, and could provide the only way of determining the primordial planetesimal population. (v) The observed clump could have originated in a collision between two runaway planetesimals, both larger than 1400 km diameter. It is unlikely that we should witness such an event unless both the formation of these runaways and the ignition of the collisional cascade occurred within the last ~10 Myr. (vi) Another explanation for Fomalhaut's clump is that ~5 per cent of the planetesimals in the ring are trapped in 1:2 resonance with a planet orbiting at 80 AU.

Abstract: Based on formulations by Heggie and by Eggleton, we present an efficient method for calculating self-consistently the tidal, spin, and dynamical evolution of a many-body system, here with particular emphasis on planetary systems. The star and innermost planet (or in general the closest pair of bodies in the system) are endowed with structure while the other bodies are treated as point masses. The evolution of the spin rates and obliquities of the extended bodies are calculated (for arbitrary initial obliquities), as is the tidal evolution of the innermost orbit. In addition, the radius of the innermost planet is evolved according to its ability to efficiently dissipate tidal energy. Relativistic effects are included to post-Newtonian order. For resonant systems such as GJ 876, the evolution equations must be integrated directly to allow for variation of the semimajor axes (other than from tidal damping) and for the possibility of instability. For systems such as Upsilon Andromedae in which the period ratio of the two inner planets is small, the innermost orbit may be averaged producing (in this case) a 50-fold reduction in the calculation time. In order to illustrate the versatility of the formulation, we consider three hypothetical primitive Earth-Moon-Sun-Jupiter systems. The parameters and initial conditions are identical in the first two models except for the Love number of the Earth, which results in dramatically different evolutionary paths. The third system is one studied by Touma & Wisdom and serves as a test of the numerical formulations presented here by reproducing two secular mean motion resonances (the evection and eviction resonances). The methods may be used for any system of bodies.

Abstract: In this article we present a detailed spectroscopic analysis of more than 50 extra-solar planet host stars. Stellar atmospheric parameters and metallicities are derived using high resolution and high S/N spectra. The spectroscopy results, added to the previous studies, imply that we have access to a large and uniform sample of metallicities for about 80 planet hosts stars. We make use of this sample to confirm the metal-rich nature of stars with planets, and to show that the planetary frequency is rising as a function of the [Fe/H]. Furthermore, the source of this high metallicity is shown to have most probably an ``primordial'' source, confirming previous results. The comparison of the orbital properties (period and eccentricity) and minimum masses of the planets with the stellar properties also reveal some emerging but still not significant trends. These are discussed and some explanations are proposed. Finally, we show that the planet host stars included in the CORALIE survey have similar kinematical properties as the whole CORALIE volume-limited planet search sample. Planet hosts simply seem to occupy the metal-rich envelope of this latter population.

Abstract: We report precise Doppler-shift measurements of 55 Cancri (G8 V) obtained from 1989 to 2002 at Lick Observatory. The velocities reveal evidence for an outer planetary companion to 55 Cancri orbiting at 5.5 AU. The velocities also conirm a second, inner planet at 0.11 AU. The outer planet is the irst extrasolar planet found that orbits near or beyond the orbit of Jupiter. It was drawn from a sample of 50 stars observed with suci ent duration and quality to detect a giant planet at 5 AU, implying that such planets are not rare. The properties of this Jupiter analog may be compared directly to those of the Jovian planets in our solar system. Its eccentricity is modest, e … 0:16, compared with e … 0:05 for both Jupiter and Saturn. Its mass is at least 4.0 MJUP (M sini). The two planets do not perturb each other signiicantly. Moreover, a third planet of sub-Jupiter mass could easily survive between these two known planets. Indeed, a third periodicity remains in the velocity measurements with P … 44:3 days and a semiamplitude of 13 m s 1 . This periodicity is caused either by a third planet at a … 0:24 AU or by inhomogeneities on the stellar surface that rotate with period 42 days. The planet interpretation is more likely, as the stellar surface is quiet both chromospherically [log﷿R 0 fi… 5 :0] and photospherically (brightness variations less than 1 mmag). Moreover, any hypothetical surface inhomogeneity would have to persist in longitude for 14 yr. Even with all three planets, an additional planet of terrestrial mass could orbit stably at 1 AU. The star 55 Cancri is apparently a normal, middle-aged main-sequence star with a mass of 0.95 M , rich in heavy elements (‰Fe=H …˛ 0 :27). This high metallicityraises the issue of the precise relationship between its age, rotation, and chromosphere. Subject headings: planetary systems N stars:individual (55 Cancri,HIP 43587,HD 75732, HR 3522, 1 Cancri)

Abstract: Gap formation in a gas disk triggered by disk-planet tidal interaction is considered. Density waves launched by the planet are assumed to be damped as a result of their nonlinear evolution leading to shock formation and its subsequent dissipation. As a consequence, wave angular momentum is transferred to the disk, leading to evolution of its surface density. Planetary migration is an important ingredient of the theory; effects of the planet-induced surface density perturbations on the migration speed are considered. A gap is assumed to form when a stationary solution for the surface density profile is no longer possible in the frame of reference migrating with the planet. An analytical limit on the planetary mass necessary to open a gap in an inviscid disk is derived. The critical mass turns out to be smaller than the mass M1 for which the planetary Hill radius equals the disk scale height by a factor of at least Q5/7 (Q is the Toomre stability parameter), depending on the strength of the migration feedback. In viscous disks the critical planetary mass could vary from ~0.2M1 to M1, depending on the disk viscosity. This implies that a gap could be formed by a planet with mass of 2-15 M⊕, depending on the disk aspect ratio, viscosity, and the planet's location in the nebula.

Abstract: We report the first astrometrically determined mass of an extrasolar planet, a companion previously detected by Doppler spectroscopy. Radial velocities first provided an ephemeris with which to schedule a significant fraction of the Hubble Space Telescope(HST) observations near companion peri- and apastron. The astrometry residuals at these orbital phases exhibit a systematic deviation consistent with a perturbation due to a planetary mass companion. Combining HST astrometry with radial velocities, we solve for the proper motion, parallax, perturbation size, inclination, and position angle of the line of nodes, while constraining period, velocity amplitude, longitude of periastron, and eccentricity to values determined from radial velocities. We find a perturbation semimajor axis and inclination, mas, , and Gl 876 absolute parallax, a p 0.25 0.06 i p 84 6 p p abs mas. Assuming that the mass of the primary star is , we find the mass of the planet, 214.6 0.2 M p 0.32 M ∗ , Gl 876b, . M p 1.89 0.34 M b Jup

Abstract: We report on a possible correlation between the masses and periods of the extrasolar planets, manifested as a paucity of massive planets with short orbital periods. Monte Carlo simulations show the effect is significant and is not solely due to an observational selection effect. We also show the effect is stronger than the one already implied by published models that assumed independent power-law distributions for the masses and periods of the extrasolar planets. Planets found in binary stellar systems may have an opposite correlation. The difference is highly significant despite the small number of planets in binary systems. We discuss the paucity of short-period massive planets in terms of some theories for the close-in giant planets. Almost all models can account for the deficit of massive planets with short periods, in particular the model that assumes migration driven by a planet-disk interaction, if the planet masses do not scale with their disk masses.

Abstract: Doppler CORALIE measurements of the solar-type stars HD 141937, HD 162020, HD 168443 and HD 202206 show Keplerian radial-velocity variations revealing the presence of 4 new companions with minimum masses close to the planet/brown-dwarf transition, namely with m2 sini= 9.7, 14.4, 16.9, and 17.5 MJup, respectively. The orbits present fairly large eccentricities (0:22 e 0:43). Except for HD 162020, the parent stars are metal rich compared to the Sun, as are most of the detected extra-solar planet hosts. Considerations of tidal dissipation in the short-period HD 162020 system points towards a brown-dwarf nature for the low-mass companion. HD 168443 is a multiple system with two low-mass companions being either brown dwarfs or formed simultaneously in the protoplanetary disks as superplanets. For HD 202206, the radial velocities show an additional drift revealing a further outer companion, the nature of which is still unknown. Finally, the stellar-host and orbital properties of massive planets are examined in comparison to lighter exoplanets. Observed trends include the need of metal-rich stars to form massive exoplanets and the lack of short periods for massive planets. If confirmed with improved statistics, these features may provide constraints for the migration scenario.