Showing papers on "Planetary system published in 2002"
TL;DR: In this paper, the exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening were presented, and the authors applied these results to the Hubble Space Telescope observations of HD 209458, showing that the ratio of the planetary to stellar radii is 0.1207 ± 0.0003.
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 light curve 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 Hubble Space Telescope 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 light curves using limb-darkening coefficients from model atmospheres that should aid in the detection, simulation, and parameter fitting of planetary transits.
2,253 citations
TL;DR: In this paper, high-precision spectrophotometric observations of four planetary transits of HD 209458, in the region of the sodium resonance doublet at 589.3 nm, were reported.
Abstract: We report high-precision spectrophotometric observations of four planetary transits of HD 209458, in the region of the sodium resonance doublet at 589.3 nm. We find that the photometric dimming during transit in a bandpass centered on the sodium feature is deeper by (2.32 ± 0.57) × 10-4 relative to simultaneous observations of the transit in adjacent bands. We interpret this additional dimming as absorption from sodium in the planetary atmosphere, as recently predicted from several theoretical modeling efforts. Our model for a cloudless planetary atmosphere with a solar abundance of sodium in atomic form predicts more sodium absorption than we observe. There are several possibilities that may account for this reduced amplitude, including reaction of atomic sodium into molecular gases and/or condensates, photoionization of sodium by the stellar flux, a low primordial abundance of sodium, and the presence of clouds high in the atmosphere.
1,300 citations
TL;DR: Measurements of tungsten isotope compositions and hafnium–tungsten ratios of several meteorites indicate that the bulk of metal–silicate separation in the Solar System was completed within <30 Myr, completely consistent with other evidence for rapid planetary formation.
Abstract: Determining the chronology for the assembly of planetary bodies in the early Solar System is essential for a complete understanding of star- and planet-formation processes. Various radionuclide chronometers (applied to meteorites) have been used to determine that basaltic lava flows on the surface of the asteroid Vesta formed within 3 million years (3 Myr) of the origin of the Solar System1,2,3. Such rapid formation is broadly consistent with astronomical observations of young stellar objects, which suggest that formation of planetary systems occurs within a few million years after star formation4,5. Some hafnium–tungsten isotope data, however, require that Vesta formed later6 (∼16 Myr after the formation of the Solar System) and that the formation of the terrestrial planets took a much longer time7,8,9,10 (62-14+4504 Myr). Here we report measurements of tungsten isotope compositions and hafnium–tungsten ratios of several meteorites. Our measurements indicate that, contrary to previous results7,8,9,10, the bulk of metal–silicate separation in the Solar System was completed within <30 Myr. These results are completely consistent with other evidence for rapid planetary formation1,2,3,4,5, and are also in agreement with dynamic accretion models11,12,13 that predict a relatively short time (∼10 Myr) for the main growth stage of terrestrial planet formation.
610 citations
TL;DR: In this paper, it was shown that the GJ 876 system is stable with respect to the eccentricity of the inner and outer planets, assuming that 1 = 2 for stable simultaneous librations of θ1 and θ2, whereas the very small eccentricities in the Io-Europa system lead to the latter's geometry.
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.
564 citations
TL;DR: In this article, the authors 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.
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.
428 citations
TL;DR: In this article, the authors investigated the formation of protoplanet systems from planetesimal disks by global (N = 5000 and 10,000 and 0.5 AU 2) growth timescale increases with a but decreases with Σ1.
Abstract: We investigate the formation of protoplanet systems from planetesimal disks by global (N = 5000 and 10,000 and 0.5 AU 2. The growth timescale increases with a but decreases with Σ1. Based on the oligarchic growth model and the conventional Jovian planet formation scenario, we discuss the diversity of planetary systems. Jovian planets can form in the disk range where the contraction timescale of planetary atmosphere and the growth timescale of protoplanets (cores) are shorter than the lifetime of the gas disk. We find that for the disk lifetime ~108 yr, several Jovian planets would form from massive disks with Σ1 30 with Uranian planets outside the Jovian planets. Only terrestrial and Uranian planets would form from light disks with Σ1 3. Solar system-like planetary systems would form from medium disks with Σ1 10.
423 citations
TL;DR: In this paper, the authors show that the radius of 51 Peg b-like planets can be reconstructed if only a small fraction 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: 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.
366 citations
TL;DR: In this article, an integral-field spectrograph coupled with a coronagraph was used to produce a data cube of two space dimensions and one wavelength for the detection of a Jovian planet at 2 pc with a 2 m coronagraphic space telescope.
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.
366 citations
TL;DR: In this article, the effect of the quadrupole moment of the parent star and of a possible second planet perturbing the orbit of the transiting planet was considered, which caused a precession of the orbital plane and of the periastron of the planet, resulting in a long-term variation of the duration and the period of transits.
Abstract: The recent discovery of a planetary transit in the star HD 209458, and the subsequent highly precise observation of the transit light curve with Hubble Space Telescope, is encouraging to search for any phenomena that might induce small changes in the light curve. Here we consider the effect of the quadrupole moment of the parent star and of a possible second planet perturbing the orbit of the transiting planet. Both of these cause a precession of the orbital plane and of the periastron of the planet, which result in a long-term variation of the duration and the period of the transits. For a transiting planet at 0.05 AU, either a quadrupole moment similar to that of the Sun or the gravitational tug from an Earth-like planet on an orbit of semimajor axis ~0.2 AU and a relative inclination near the optimal 45° would cause a transit duration time derivative of ~1 s yr-1.
306 citations
TL;DR: In this paper, the authors examined 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 and showed that solar-like variability does not prevent the detection of Earth-sized planets even for stars rotating significantly faster than the Sun.
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
274 citations
TL;DR: In this paper, the formation of organic molecules in space has been studied and the physical and chemical conditions, including density, temperature, ultraviolet (UV) radiation and energetic particles, have been used to determine reaction pathways and the complexity of organic molecule in different space environments.
Abstract: Stellar nucleosynthesis of heavy elements such as carbon allowed the formation of organic molecules in space, which appear to be widespread in our Galaxy. The physical and chemical conditions—including density, temperature, ultraviolet (UV) radiation and energetic particles—determine reaction pathways and the complexity of organic molecules in different space environments. Dense interstellar clouds are the birth sites of stars of all masses and their planetary systems. During the protostellar collapse, interstellar organic molecules in gaseous and solid phases are integrated into protostellar disks from which planets and smaller solar
TL;DR: In this article, the authors investigate the long-term dynamical stability of hypothetical moons orbiting extrasolar giant planets and derive an upper mass limit for those satellites that might have survived to the present day.
Abstract: We investigate the long-term dynamical stability of hypothetical moons orbiting extrasolar giant planets. Stellar tides brake a planet's rotation and, together with tidal migration, act to remove satellites; this process limits the lifetimes of larger moons in extrasolar planetary systems. Because more massive satellites are removed more quickly than less massive ones, we are able to derive an upper mass limit for those satellites that might have survived to the present day. For example, we estimate that no primordial satellites with masses greater than 7 × 10-7 M⊕ (~70 km radius for ρ = 3 g cm-3) could have survived around the transiting planet HD 209458b for the age of the system. No meaningful mass limits can be placed on moons orbiting Jovian planets more than ~0.6 AU from their parent stars. Earthlike moons of Jovian planets could exist for 5 Gyr in systems where the stellar mass is greater than 0.15 M☉. Transits show the most promise for the discovery of extrasolar moons—we discuss prospects for satellite detection via transits using space-based photometric surveys and the limits on the planetary tidal dissipation factor Qp that a discovery would imply.
01 Nov 2002
TL;DR: In this paper, the formation of organic molecules in space has been studied and the physical and chemical conditions, including density, temperature, ultraviolet (UV) radiation and energetic particles, have been used to determine reaction pathways and the complexity of organic molecule in different space environments.
Abstract: Stellar nucleosynthesis of heavy elements such as carbon allowed the formation of organic molecules in space, which appear to be widespread in our Galaxy. The physical and chemical conditions—including density, temperature, ultraviolet (UV) radiation and energetic particles—determine reaction pathways and the complexity of organic molecules in different space environments. Dense interstellar clouds are the birth sites of stars of all masses and their planetary systems. During the protostellar collapse, interstellar organic molecules in gaseous and solid phases are integrated into protostellar disks from which planets and smaller solar
TL;DR: In this paper, the K giant ι Dra (HD 137759, HR 5744, HIP 75458) was found to have a substellar companion orbiting the primary star, which is the first brown dwarf or planet to orbit a giant rather than a main-sequence star.
Abstract: We report precise radial velocity measurements of the K giant ι Dra (HD 137759, HR 5744, HIP 75458), carried out at Lick Observatory, which reveal the presence of a substellar companion orbiting the primary star. A Keplerian fit to the data yields an orbital period of about 536 days and an eccentricity of 0.70. Assuming a mass of 1.05 M☉ for ι Dra, the mass function implies a minimum companion mass m2 sin i of 8.9 MJ, making it a planet candidate. The corresponding semimajor axis is 1.3 AU. The nondetection of the orbital motion by Hipparcos allows us to place an upper limit of 45 MJ on the companion mass, establishing the substellar nature of the object. We estimate that transits in this system could occur already for inclinations as low as 815, as a result of the large diameter of the giant star. The companion to ι Dra is the first brown dwarf or planet found to orbit a giant rather than a main-sequence star.
TL;DR: In this article, the authors present a method for calculating self-consistently the tidal, spin, and dynamical evolution of a many-body system, here with particular emphasis on planetary systems.
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: 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.
TL;DR: In this paper, a possible correlation between the masses and periods of the extrasolar planets, manifested as a paucity of massive planets with short orbital periods, was reported, and Monte Carlo simulations show the effect is significant and is not solely due to an observational selection effect.
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.
TL;DR: In this paper, empirical methods for setting appropriate detection thresholds and for establishing the confidence level in planetary candidates obtained from transit photometry of even a large number of stars are presented. But the success of these efforts depends in part on the ability to establish appropriate detection threshold to control false alarm rates and assess the statistical confidence in planetary candidate drawn from any such search.
Abstract: Increased attention is being paid to transit photometry as a viable method for discovering or confirming detections of extrasolar planets. Several ground-based efforts are underway that target short-period, giant planets such as 51 Peg b, and several missions have been proposed to NASA and ESA to detect planets as small as Earth from spaceborne photometers. The success of these efforts depends in part on the ability to establish appropriate detection thresholds to control false alarm rates and the ability to assess the statistical confidence in planetary candidates drawn from any such search. This latter function attains higher importance for the space-based efforts, where direct ground-based confirmation of terrestrial-size planets is not possible. These tasks are complicated by the need to survey tens of thousands of stars to overcome the limited geometric probability of transit alignment and by the nature of the transit signals themselves. In this paper, we present empirical methods for setting appropriate detection thresholds and for establishing the confidence level in planetary candidates obtained from transit photometry of even a large number of stars. The methods are simple and allow the observer to quickly assess the statistical significance of any particular set of transits.
TL;DR: In this paper, a space-based gravitational microlensing survey for terrestrial extrasolar planets is proposed, which can provide a nearly complete picture of the properties of planetary systems in our Galaxy.
Abstract: We show that a space-based gravitational microlensing survey for terrestrial extrasolar planets is feasible in the near future and could provide a nearly complete picture of the properties of planetary systems in our Galaxy. We present simulations of such a survey using a 1-2 m aperture space telescope with a ~2 deg2 field of view to continuously monitor ~108 Galactic bulge main-sequence stars. The microlensing techniques allow the discovery of low-mass planets with high signal-to-noise ratio, and the space missions that we have studied are sensitive to planets with masses as low as that of Mars. By targeting main-sequence source stars, which can only be resolved from space, the space-based microlensing survey is able to detect enough light from the lens stars to determine the spectral type of one-third of the lens stars with detected planets, including virtually all of the F, G, and K stars, which comprise one-quarter of the event sample. This enables the determination of the planetary masses and separations in physical units as well as the abundance of planets as a function of stellar type and distance from the Galactic center. We show that a space-based microlensing planet search program has its highest sensitivity to planets at orbital separations of 0.7-10 AU, but it will also have significant sensitivity at larger separations and will be able to detect free-floating planets in significant numbers. This complements the planned terrestrial planet transit missions, which are sensitive to terrestrial planets at separations of ?1 AU. Such a mission should also detect ~50,000 giant planets via transits, and it is, therefore, the only proposed planet detection method that is sensitive to planets at all orbital radii.
TL;DR: In this paper, a combination of high-resolution and wide-field imaging reveals two binary stars and one triple star system among the sample of the first 11 stars with planets detected by radial velocity variations.
Abstract: A combination of high-resolution and wide-field imaging reveals two binary stars and one triple star system among the sample of the first 11 stars with planets detected by radial velocity variations. High-resolution speckle or adaptive optics (AO) data probe subarcsecond scales down to the diffraction limit of the Keck 10 m or the Lick 3 m, and direct images or AO images are sensitive to a wider field, extending to 10'' or 38'', depending on the camera. One of the binary system—HD 114762—was not previously known to be a spatially resolved multiple system; additional data taken with the combination of Keck adaptive optics and NIRSPEC are used to characterize the new companion. The second binary system—τ Boo—was a known multiple with two conflicting orbital solutions; the current data will help constrain the discrepant estimates of periastron time and separation. Another target—16 Cyg B—was a known common proper motion binary, but the current data resolve a new third component, close to the wide companion 16 Cyg A. Both the HD 114762 and 16 Cyg B systems harbor planets in eccentric orbits, while the τ Boo binary contains an extremely close planet in a tidally circularized orbit. Although the sample is currently small, the proportion of binary systems is comparable to that measured in the field over a similar separation range. Incorporating the null result from another companion search project lowers the overall fraction of planets in binary systems, but the detections in our survey reveal that planets can form in binaries separated by less than 50 AU.
TL;DR: In this article, the first astrometrically determined mass of an extrasolar planet, a companion previously detected by Doppler spectroscopy, was reported, and 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.
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
TL;DR: In this paper, a suite of disk instability models calculated with a three-dimensional, gravitational hydrodynamics code is presented, where the authors explore the effects of varying the thermodynamic assumptions, the initial degree of gravitational instability, and the numerical spatial resolution.
Abstract: Disk instability is a promising mechanism for explaining the rapid formation of the gas and ice giant planets in our solar system as well as in extrasolar planetary systems. Disk instability involves the formation of self-gravitating clumps in marginally gravitationally unstable protoplanetary disks on timescales of ~1000 yr. We present here the results of a suite of disk instability models calculated with a three-dimensional, gravitational hydrodynamics code. The models explore the effects of varying the thermodynamical assumptions, the initial degree of gravitational instability, and the numerical spatial resolution. For all models, the disk has an initial mass of 0.091 M☉ inside 20 AU, in orbit around a 1 M☉ protostar. The most realistic models are calculated with an energy equation and diffusion approximation radiative transfer, which produces results intermediate between those of models with a locally isothermal or locally adiabatic thermodynamic response to the growth of azimuthal density perturbations. Locally adiabatic models suppress the growth of clumps, while radiative transfer models permit the formation of clumps similar to those in locally isothermal models. Vertical convection is identified as the primary means for cooling the midplane in the models with radiative transfer. These models suggest that the disk instability mechanism is capable of rapidly forming self-gravitating protoplanets in marginally unstable disks with a mass similar to that inferred for the solar nebula and for other protoplanetary disks. Assuming that the protoplanets survive their subsequent evolution, the likelihood that all protoplanetary disks pass through a phase of marginal gravitational instability might then imply a high frequency of extrasolar giant planets.
TL;DR: In this article, it was shown that if disk instability is the primary formation mechanism for extrasolar gas giant planets, even relatively low-metallicity galactic disk stars should harbor gas giant planet formation.
Abstract: Spectroscopic searches for extrasolar planets are most successful when the target star has high metallicity, a trend that may be caused by observational selection effects, pollution by ingested planetary material, or a requirement of high metallicity for gas giant planet formation. We show that in the scenario of the disk instability mechanism for forming gas giant protoplanets, clump-forming gravitational instabilities proceed in much the same manner in protoplanetary disks with metallicities that vary by factors of 10 greater or less than that of a standard disk model. This remarkable insensitivity to the dust grain opacity is attributed to radiative energy losses from the disks being controlled more by their being embedded in a thermal bath determined by their central protostar than by radiative fluxes deep within the disks' optically thick midplanes. This result suggests that if disk instability is the primary formation mechanism for extrasolar gas giant planets, even relatively low-metallicity galactic disk stars should harbor gas giant planets.
TL;DR: In this article, the authors explore the possibility that extrasolar planets might be found in the 1 : 1 mean motion resonance, in which a pair of planets share a time-averaged orbital period.
Abstract: We explore the possibility that extrasolar planets might be found in the 1 : 1 mean motion resonance, in which a pair of planets share a time-averaged orbital period. There are a variety of stable co-orbital configurations, and we specifically examine three different versions of the 1 : 1 resonance. In the first configuration, the two planets and the star participate in tadpole-type librations about the vertices of an equilateral triangle. The dynamics of this situation resemble the orbits of Jupiter's Trojan asteroids. We show analytically that an equilateral configuration consisting of a star and two equal-mass planets is linearly stable for mass ratios μ = 2mpl/(2mpl + M*) < 0.03812. When the equilateral configuration is subjected to larger perturbations, a related 1 : 1 resonance occurs. In this second family of configurations, the planet pair executes horseshoe-type orbits in which the librating motion in the corotating frame is symmetric about a 180° separation. The Saturnian satellites Janus and Epimetheus provide a solar system example of this phenomenon. In the case of equal-mass planets, a numerical survey indicates that horseshoe configurations are stable over long periods for mass ratios μ < 0.0004, indicating that a pair of Saturn-mass planets can exist in this resonance. The third configuration that we examine is more exotic and involves a pair of planets that exchange angular momentum in a manner that allows them to indefinitely avoid close encounters. An illustrative example of this resonance occurs when one planet has a highly eccentric orbit while the other planet moves on a nearly circular orbit; the periapses are in alignment, and conjunctions occur near periapse. All three of these resonant configurations can be stable over timescales comparable to or longer than stellar lifetimes. We show that pairs of planets in 1 : 1 resonance yield characteristic radial velocity signatures that are not prone to the sin i degeneracy. Indeed, Keplerian fits to the radial velocities cannot reveal the presence of two planets in the 1 : 1 resonance. We discuss a dynamical fitting method for such systems and illustrate its use with a simulated data set. Finally, we argue that hydrodynamic simulations and torqued three-body simulations indicate that 1 : 1 resonant pairs might readily form and migrate within protostellar disks.
TL;DR: In this paper, the morphology of the Eridani dust ring is reproduced by a numerical simulation of dust particles captured into the 5 : 3 and 3 : 2 exterior mean motion resonances with a 0.3 eccentricity 10-4 M☉ planet at periastron at a semimajor axis of 40 AU.
Abstract: The morphology of the Eridani dust ring is reproduced by a numerical simulation of dust particles captured into the 5 : 3 and 3 : 2 exterior mean motion resonances with a 0.3 eccentricity 10-4 M☉ planet at periastron at a semimajor axis of 40 AU. The morphology will differ when the planet is at apastron, in about 140 yr. Moderate eccentricity planets in outer extrasolar systems will cause observable variations in the morphology of associated dusty rings.
TL;DR: The mass distribution of extrasolar planets continues to exhibit a rapid rise from 10 MJUP toward the lowest detectable masses near 1 MSAT as discussed by the authors, characterized by nearly circular orbits and orbital radii greater than 1 AU.
Abstract: Ten new companions have emerged from the Keck precision Doppler velocity survey, with minimum (M sin i) masses ranging from 0.8 MJUP to 0.34 M☉. Five of these are planet candidates with M sin i < 12 MJUP, two are brown dwarf candidates with M sin i ~ 30 MJUP, and three are low-mass stellar companions. Hipparcos astrometry reveals the orbital inclinations and masses for three of the (more massive) companions, and it provides upper limits to the masses for the rest. A new class of extrasolar planet is emerging, characterized by nearly circular orbits and orbital radii greater than 1 AU. The planet HD 4208b appears to be a member of this new class. The mass distribution of extrasolar planets continues to exhibit a rapid rise from 10 MJUP toward the lowest detectable masses near 1 MSAT.
TL;DR: In this paper, the authors numerically model the orbital evolution of Kuiper belt (KB) dust and estimate its equilibrium spatial distribution and its brightness and spectral energy distribution, assuming graybody absorption and emission by the dust grains.
Abstract: The dust produced in the Kuiper belt (KB) spreads throughout the solar system, forming a dust disk. We numerically model the orbital evolution of KB dust and estimate its equilibrium spatial distribution and its brightness and spectral energy distribution (SED), assuming graybody absorption and emission by the dust grains. We show that the planets modify the KB disk SED, so potentially we can infer the presence of planets in spatially unresolved debris disks by studying the shape of their SEDs. We point out that there are inherent uncertainties in the prediction of structure in the dust disk, owing to the chaotic dynamics of dust orbital evolution imposed by resonant gravitational perturbations of the planets.
TL;DR: In this paper, the authors analyze 5 years of PLANET photometry of microlensing events toward the Galactic bulge to search for the short-duration deviations from single-lens light curves that are indicative of the presence of planetary companions to the primary microlenses.
Abstract: We analyze 5 years of PLANET photometry of microlensing events toward the Galactic bulge to search for the short-duration deviations from single-lens light curves that are indicative of the presence of planetary companions to the primary microlenses. Using strict event-selection criteria, we construct a well-defined sample of 43 intensively monitored events. We search for planetary perturbations in these events over a densely sampled region of parameter space spanning two decades in mass ratio and projected separation, but find no viable planetary candidates. By combining the detection efficiencies of the events, we find that, at 95% confidence, less than 25% of our primary lenses have companions with mass ratio q = 10-2 and separations in the lensing zone, [0.6-1.6]θE, where θE is the Einstein ring radius. Using a model of the mass, velocity, and spatial distribution of bulge lenses, we infer that the majority of our lenses are likely M dwarfs in the Galactic bulge. We conclude that less than 33% of M dwarfs in the Galactic bulge have companions with mass mp = MJ between 1.5 and 4 AU, and less than 45% have companions with mp = 3MJ between 1 and 7 AU, the first significant limits on planetary companions to M dwarfs. We consider the effects of the finite size of the source stars and changing our detection criterion, but find that these do not alter our conclusions substantially.
TL;DR: In this article, a computer code for precise measurements of stellar radial velocity variations with iodine (I2) cells attached to the HDS on Subaru Telescope and the HIgh Dispersion Echelle Spectrograph (HIDES) on Okayama 188cm reflector was developed.
Abstract: We have developed a computer code for precise measurements of stellar radial velocity variations with iodine (I2) cells attached to the High Dispersion Spectrograph (HDS) on Subaru Telescope and the HIgh Dispersion Echelle Spectrograph (HIDES) on Okayama 188cm reflector. Our modeling technique for I2 data is similar to those described by Butler et al. (1996, AAA 65.036.447) and Valenti et al. (1995, AAA 64.036.209) concerning the point that the stellar spectrum taken through the I2 cell (star + I2 spectrum) is modeled as the product of high-resolution stellar and I2 template spectra convolved with the modeled instrumental profile (IP) of the spectrograph. In order to generate a template stellar spectrum, we have devised a new method to extract an intrinsic stellar spectrum from observed star + I2 spectra. This enables us to obtain a well-established template stellar spectrum even in cases when the IP and the wavelength scale are apt to vary with time and the observational conditions, and the existing method which reconstructs the IP from a B-star + I2 spectrum (Butler et al. 1996; Endl et al. 2000, A&A, 362, 585) fails. We here report on the results of our Doppler measurements of three solar-type stars, 16 Cyg B, τ Cet, and υ And, based on data collected with HDS and HIDES for about one year. These results show that we have achieved a precision of about 5–6ms −1 over a time span of one year with our current analysis package with both spectrographs.
TL;DR: In this article, the presence of two extrasolar planets orbiting the star 47 UMa was confirmed by precise Doppler velocity measurements during 13 yr at Lick Observatory, and the residuals to that single-Keplerian fit exhibit a periodicity that is consistent with an additional planetary companion.
Abstract: Precise Doppler velocity measurements during 13 yr at Lick Observatory reveal the presence of two planets orbiting the star 47 UMa. The previously detected inner planet is confirmed by the newer velocities that yield a revised orbital period Pb = 1089.0 ± 2.9 days, M sin i = 2.54 MJ, and eccentricity eb = 0.061 ± 0.014. The residuals to that single-Keplerian fit exhibit a periodicity that is consistent with an additional planetary companion. A simultaneous fit for both planets implies that the outer planet has Pc = 2594 ± 90 days, a = 3.73 AU, 0 < ec < 0.2, and M sin i = 0.76 MJ. Its semimajor axis is the largest yet found for an extrasolar planet, and its angular separation from the host star of 026 makes it a good target for direct detection and astrometry. Hipparcos astrometry places limits on the masses of these planets at less than ~10 MJ, and dynamical modeling places limits on both ec and the orbital inclinations. The outer planet induces a velocity semiamplitude of K = 11.1 m s-1 in the star during its 7 yr orbit, similar to the signal induced on the sun by Jupiter.