Showing papers on "Exoplanet published in 2002"
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.
1,534 citations
TL;DR: In this article, the authors presented the discovery of two Saturn-mass companions to HD 108147 and HD 168746 by means of the CORALIE echelle spectrograph.
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.
685 citations
TL;DR: It is found that both the mid-IR and the visible to near-IR wavelength ranges offer valuable information regarding biosignatures and planetary properties; therefore both merit serious scientific consideration for TPF and Darwin.
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...
643 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.
448 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.
396 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
368 citations
TL;DR: In this article, a three-dimensional general circulation climate model and a one-dimensional energy-balance model were used to examine the climates of either bound or isolated earths on extremely elliptical orbits near the HZ.
Abstract: Many of the recently discovered extrasolar giant planets move around their stars on highly eccentric orbits, and some with e & 0-7. Systems with planets within or near the habitable zone (HZ) will possibly harbour life on terrestrial-type moons if the seasonal temperature extremes resulting from the large orbital eccentricities of the planets are not too severe. Here we use a three-dimensional general- circulation climate model and a one-dimensional energy-balance model to examine the climates of either bound or isolated earths on extremely elliptical orbits near the HZ. While such worlds are susceptible to large variations in surface temperature, long-term climate stability depends primarily on the average stellar flux received over an entire orbit, not the length of the time spent within the HZ.
316 citations
TL;DR: In this paper, the authors examined outcomes of such evolution in systems of three Jupiter-mass planets around a solar-mass star by integration of their orbits in three dimensions, and found that the most common outcome of gravitational scattering by close encounters is hyperbolic ejection of one planet.
307 citations
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.
294 citations
TL;DR: In this article, the spectral deconvolution method was proposed to eliminate the contribution from the star while preserving both the flux and spectrum of the extrasolar planet, and the spectral characteristics of the exoplanets were obtained naturally as part of this process.
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.
253 citations
TL;DR: In this article, a detailed spectroscopic analysis of more than 50 extra-solar planet host stars is presented, where atmospheric parameters and metallicities are derived using high resolution and high S/N spectra.
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.
TL;DR: In this article, a photochemical and radiative-convective model of terrestrial planet atmospheres is presented, and it is shown that O2-rich atmospheres (up to 5%) and IR absorbing O3 layers can build up without life from H2 Oa nd CO2 photolysis.
Abstract: Darwin (ESA) and Terrestrial Planet Finder-TPF (NASA) are two projects of space telescopes aiming at the detection of extra-solar terrestrial planets and some of their atmospheric components. In particular, they will be sensitive to the 9.6 mb and of O 3 which may be the signature of an O2-rich atmosphere produced by photosynthetic life forms. In this paper, we point out that O2, and hence O3, can also be produced by photochemistry and we investigate the risk of \false positive" detection of life incurred by these missions. For this purpose, we have developed new photochemical and radiative-convective models of terrestrial planet atmospheres. By modelling the photochemistry of some realistic atmospheres, (including present and past Earth and Mars) we show that O2-rich atmospheres (up to 5%) and IR absorbing O3 layers can build up without life from H2 Oa nd CO2 photolysis. However, Darwin can still provide a reliable way to detect, through their mid-infrared signatures, ecosystems which have developed oxygenic photosynthesis. Indeed, the two photochemical sources of O2 are shown to interfere with each other; second, when the CO2 pressure is high enough (>50 mbar) to produce appreciable amounts of O2 and O3 ,i t also masks the O 3 feature; and third, the by-products of H2O photolysis destroy O3 .A s a result, whereas the unique detection of O2 remains ambiguous, the simultaneous infrared detection of O3 ,C O 2 and H2O, provided by Darwin, is established to be a robust way to discriminate photochemical O2 production from biological photosynthesis: none of the atmospheres modelled exhibits this \triple signature", even in the most extreme \high risk" cases.
TL;DR: In this article, precise Doppler-shift measurements of 55 Cancri (G8 V) obtained from 1989 to 2002 at Lick Observatory were obtained from a sample of 50 stars observed with varying duration and quality to detect a giant planet at 5.5 AU.
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)
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 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: 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 as mentioned in this paper.
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.
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 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: Doppler CORALIE measurements of the solar-type stars HD141937, HD162020, HD168443 and HD202206 reveal the presence of 4 new companions with minimum masses close to the planet/brown-dwarf transition, namely with m_2sin(i) = 9.7, 14.4, 16.9, and 17.5 M_Jup, respectively as mentioned in this paper.
Abstract: Doppler CORALIE measurements of the solar-type stars HD141937, HD162020, HD168443 and HD202206 show Keplerian radial-velocity variations revealing the presence of 4 new companions with minimum masses close to the planet/brown-dwarf transition, namely with m_2sin(i) = 9.7, 14.4, 16.9, and 17.5 M_Jup, respectively. The orbits present fairly large eccentricities (0.22
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 paper, 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 {\it 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 {\it 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 semi-major axis and inclination, $\alpha$ = 0.25 $\pm$ 0.06 mas, $i$ = 84\arcdeg $\pm$6\arcdeg, and Gl 876 absolute parallax, $\pi_{abs}= 214.6 \pm$ 0.2 mas. Assuming that the mass of the primary star is $M_* = 0.32M_{\sun}$, we find the mass of the planet, Gl 876b, $M_b = 1.89\pm0.34M_{Jup}$.
TL;DR: For a Sun-sized star and a Jupiter-sized planet, the normalized flux difference in the transit ingress/egress light curve between a spherical and an oblate planet is a few to 15 × 10-5 for oblateness similar to Jupiter and Saturn, respectively as discussed by the authors.
Abstract: The solar system gas giant planets are oblate due to their rapid rotation. A measurement of the planet's projected oblateness would constrain the planet's rotational period. Planets that are synchronously rotating with their orbital revolution will be rotating too slowly to be significantly oblate; these include planets with orbital semimajor axes 0.2 AU (for MP ~ MJupiter and M* ~ M☉). Jupiter-like planets in the range of orbital semimajor axis 0.1 to 0.2 AU will tidally evolve to synchronous rotation on a timescale similar to main-sequence stars' lifetimes. In this case, an oblateness detection will help constrain the planet's tidal Q value. The projected oblateness of a transiting extrasolar giant planet is measurable from a very high photometric precision transit light curve. For a Sun-sized star and a Jupiter-sized planet, the normalized flux difference in the transit ingress/egress light curve between a spherical and an oblate planet is a few to 15 × 10-5 for oblateness similar to Jupiter and Saturn, respectively. The transit ingress and egress are asymmetric for an oblate planet with orbital inclination different from 90° and a nonzero projected obliquity. A photometric precision of 10-4 has been reached by Hubble Space Telescope (HST) observations of the known transiting extrasolar planet HD 209458b. Kepler, a NASA discovery-class mission designed to detect transiting Earth-sized planets, requires a photometric precision of 10-5 and expects to find 30 to 40 transiting giant planets with orbital semimajor axes 0.2 AU. Furthermore, part-per-million photometric precision (reached after averaging over several orbital periods) is expected from three other space telescopes to be launched within the next three years. Thus, an oblateness measurement of a transiting giant planet is realistic in the near future.
TL;DR: In this article, a statistical study of the post-formation migration of giant planets in a range of initial disk conditions is presented, and it is shown that the current distribution of extrasolar giant planet masses implies that high mass giant planet formation must be relatively rare.
Abstract: We present a statistical study of the post-formation migration of giant planets in a range of initial disk conditions. For given initial conditions we model the evolution of giant planet orbits under the influence of disk, stellar, and mass loss torques. We determine the mass and semi-major axis distribution of surviving planets after disk dissipation, for various disk masses, lifetimes, viscosities, and initial planet masses. The majority of planets migrate too fast and are destroyed via mass transfer onto the central star. Most surviving planets have relatively large orbital semi-major axes of several AU or larger. We conclude that the extrasolar planets observed to date, particularly those with small semi-major axes, represent only a small fraction (∼25% to 33%) of a larger cohort of giant planets around solar-type stars, and many undetected giant planets must exist at large (>1-2 AU) distances from their parent stars. As sensitivity and completion of the observed sample increase with time, this distant majority population of giant planets should be revealed. We find that the current distribution of extrasolar giant planet masses implies that high mass (more than 1-2 Jupiter masses) giant planet formation must be relatively rare. Finally, our simulations imply that the efficiency of giant planet formation must be high: at least 10% and perhaps as many as 80% of solar-type stars possess giant planets during their pre-main sequence phase. These predictions, including those for pre-main sequence stars, are testable with the next generation of ground- and space-based planet detection techniques.
TL;DR: The projected oblateness of a transiting extrasolar giant planet is measured from a very high-photometric-precision transit light curve as mentioned in this paper, where the transit ingress and egress are asymmetric for an oblate planet with an orbital inclination different from 90 degrees.
Abstract: (Abridged) The solar system gas giant planets are oblate due to their rapid rotation. A measurement of the planet's projected oblateness would constrain the planet's rotational period. Planets that are synchronously rotating with their orbital revolution will be rotating too slowly to be significantly oblate; these include planets with orbital semi-major axes <~ 0.2AU (for M_P ~ M_J and M_* ~ M_sun). Jupiter-like planets in the range of orbital semi-major axes 0.1 AU to 0.2 AU will tidally evolve to synchronous rotation on a timescale similar to main sequence stars' lifetimes. In this case an oblateness detection will help constrain the planet's tidal Q value.
The projected oblateness of a transiting extrasolar giant planet is measurable from a very high-photometric-precision transit light curve. For a sun-sized star and a Jupiter-sized planet the normalized flux difference in the transit ingress/egress light curve between a spherical and an oblate planet is a few to 15 x 10^{-5} for oblateness similar to Jupiter and Saturn respectively. The transit ingress and egress are asymmetric for an oblate planet with an orbital inclination different from 90 degrees and a non-zero projected obliquity. A photometric precision of 10^{-4} has been reached by HST observations of the known transiting extrasolar planet HD209458b. In addition several planned space missions (including MOST, MONS, Corot, and Kepler) will study or find transiting giant planets with photometric precision 0.2 AU.
TL;DR: In this paper, a statistical study of the post-formation migration of giant planets in a range of initial disk conditions is presented, and it is shown that the majority of surviving giant planets have relatively large orbital semi-major axes of several AU or larger.
Abstract: We present a statistical study of the post-formation migration of giant planets in a range of initial disk conditions. For given initial conditions we model the evolution of giant planet orbits under the influence of disk, stellar, and mass loss torques. We determine the mass and semi-major axis distribution of surviving planets after disk dissipation, for various disk masses, lifetimes, viscosities, and initial planet masses. The majority of planets migrate too fast and are destroyed via mass transfer onto the central star. Most surviving planets have relatively large orbital semi-major axes of several AU or larger. We conclude that the extrasolar planets observed to date, particularly those with small semi-major axes, represent only a small fraction (~25% to 33%) of a larger cohort of giant planets around solar-type stars, and many undetected giant planets must exist at large (>1-2 AU) distances from their parent stars. As sensitivity and completion of the observed sample increases with time, this distant majority population of giant planets should be revealed. We find that the current distribution of extrasolar giant planet masses implies that high mass (more than 1-2 Jupiter masses) giant planet formation must be relatively rare. Finally, our simulations imply that the efficiency of giant planet formation must be high: at least 10% and perhaps as many as 80% of solar-type stars possess giant planets during their pre-main sequence phase. These predictions, including those for pre-main sequence stars, are testable with the next generation of ground- and space-based planet detection techniques
TL;DR: In this article, the authors examine the overall likelihood that the consumption of a giant planet could pollute its host star and examine whether dynamical processes could bring a giant Planet close enough to the star to destroy it and whether the destruction of a planet would necessarily affect other planets in the system.
Abstract: Given the high metal contents observed for many stars with planets (SWPs), we examine the overall likelihood that the consumption of a giant planet could pollute its host star. First, we discuss 6Li and 7Li as indicators of pollution, verifying that 6Li is a strong indicator of pollution 30 Myr after star formation and showing that it strongly constrains the amount of heavy-element pollution incorporated into the star. Detection of 6Li in SWPs could also be used to distinguish between giant planet formation theories and can be used to detect the consumption of giant planets independent of planet mass. Second, we examine the probability that giant planets between 1 and 3 MJ could be destroyed in the outer convection zone of stars slightly more massive than the Sun (for which detection of a chemical signature of pollution would be easiest). We find that heated giant planets would be efficiently destroyed near the surface of the star, while the cores of cold giant planets might be able to survive a plunge through the base of the star's convection zone. Third, we examine whether dynamical processes could bring a giant planet close enough to the star to destroy it and whether the destruction of a planet would necessarily affect other planets in the system. While tidal interaction between protoplanets and their nascent disks may have led them to the proximity of their host stars, postformation star-planet interaction can lead to tidal disruption of the planet and accretion of its material or orbital decay followed by hydrodynamical interaction. Throughout, we consider the case of HD 82943, a star with a preliminary detection of 6Li that is known to have two planets. Using stellar models including diffusion, we estimate the mass of HD 82943 to be ~1.2 M☉ and its age to be ~0.5-1.5 Gyr. The observed 7Li abundance for HD 82943 is consistent with stars of similar Teff and age in the open cluster NGC 752. We describe a possible dynamical history for a hypothetical planet in the presence of the two resonant planets currently known. We present stable orbital configurations in which the hypothetical planet has low eccentricity and semimajor axis near 0.02 AU, so that it is dynamically decoupled from the resonant planets. Tidal interactions with the slowly rotating star can subsequently drag the planet into the stellar surface within the age of the star.
TL;DR: In this paper, the authors investigate the effect of satellites in the magnification pattern near the region of the planet-induced perturbations by performing realistic simulations of Galactic bulge microlensing events and find that detecting satellite signals in lensing light curves will be very difficult because the signals are seriously smeared out by the severe finite-source effect even for events involved with source stars with small angular radii.
Abstract: Although many methods of detecting extrasolar planets have been proposed and successful implementation of some of these methods enabled a rapidly increasing number of exoplanet detections, little has been discussed about the method of detecting satellites around exoplanets. In this paper we test the feasibility of detecting satellites of exoplanets via microlensing. For this purpose, we investigate the effect of satellites in the magnification pattern near the region of the planet-induced perturbations by performing realistic simulations of Galactic bulge microlensing events. From this investigation, we find that although satellites can often cause alterations of magnification patterns, detecting satellite signals in lensing light curves will be very difficult because the signals are seriously smeared out by the severe finite-source effect even for events involved with source stars with small angular radii.
TL;DR: In this paper, the authors reported precise Doppler measurements of the stars HD 216437, HD 196050 and HD 160691 using the UCLES spectrometer together with an iodine cell as part of the Anglo-Australian Planet Search.
Abstract: We report precise Doppler measurements of the stars HD 216437, HD 196050 and HD 160691 obtained with the Anglo-Australian Telescope using the UCLES spectrometer together with an iodine cell as part of the Anglo-Australian Planet Search. Our measurements reveal periodic Keplerian velocity variations that we interpret as evidence for planets in orbit around these solar type stars. HD 216437 has a period of 1294$\pm$250 d, a semi-amplitude of 38$\pm$4 m s$^{-1}$ and of an eccentricity of 0.33$\pm$0.09. The minimum (M sin $i$) mass of the companion is 2.1$\pm$0.3 M$_{\rm JUP}$ and the semi-major axis is 2.4$\pm$0.5 au. HD 196050 has a period of 1288$\pm$230 d, a semi-amplitude of 54$\pm$8 m s$^{-1}$ and an eccentricity of 0.28$\pm$0.15. The minimum mass of the companion is 3.0$\pm$0.5 M$_{\rm JUP}$ and the semi-major axis is 2.3$\pm$0.5 au. We also report further observations of the metal rich planet bearing star HD 160691. Our new solution confirms the previously reported planet and shows a trend indicating a second, longer-period companion. These discoveries add to the growing numbers of midly-eccentric, long-period extra-solar planets around Sun-like stars. As seems to be typical of stars with planets, both stars are metal-rich.
1 Dec 2002
TL;DR: For example, this article found that methanethiol and related organosulfur compounds (as well as carbon dioxide) absorb at wavelengths near or overlapping the 9.6-microm band of ozone, and there is potential ambiguity in interpreting a feature around this wavelength in an extrasolar planet spectrum.
Abstract: A major goal of NASA's Origins Program is to find habitable planets around other stars and determine which might harbor life. Determining whether or not an extrasolar planet harbors life requires an understanding of what spectral features (i.e., biosignatures) might result from life's presence. Consideration of potential biosignatures has tended to focus on spectral features of gases in Earth's modern atmosphere, particularly ozone, the photolytic product of biogenically produced molecular oxygen. But life existed on Earth for about 1(1/2) billion years before the buildup of atmospheric oxygen. Inferred characteristics of Earth's earliest biosphere and studies of modern microbial ecosystems that share some of those characteristics suggest that organosulfur compounds, particularly methanethiol (CH(3)SH, the sulfur analog of methanol), may have been biogenic products on early Earth. Similar production could take place on extrasolar Earth-like planets whose biota share functional chemical characteristics with Earth life. Since methanethiol and related organosulfur compounds (as well as carbon dioxide) absorb at wavelengths near or overlapping the 9.6-microm band of ozone, there is potential ambiguity in interpreting a feature around this wavelength in an extrasolar planet spectrum.
TL;DR: In this paper, the authors examined how atmospheric lensing and (projected) planet oblateness/ellipticity modify transit light curves and found that the fractional change in the diminution of starlight is approximately the ratio of atmospheric scale height to planet radius.
Abstract: Future high-precision photometric measurements of transiting extrasolar planets promise to tell us much about the characteristics of these systems. We examine how atmospheric lensing and (projected) planet oblateness/ellipticity modify transit light curves. The large density gradients expected in planet atmospheres can offset the unfavorably large observer lens–to–source lens distance ratio and allow the existence of caustics. Under such conditions of strong lensing, which we quantify with an analytic expression, starlight from all points in the planet’s shadow is refracted into view, producing a characteristic slowing down of the dimming at ingress (vice versa for egress). A search over several parameters, such as the limb-darkening profile, the planet radius, the transit speed, and the transit geometry, cannot produce a nonlensed transit light curve that can mimic a lensed light curve. The fractional change in the diminution of starlight is approximately the ratio of atmospheric scale height to planet radius, expected to be 1% or less. The lensing signal varies strongly with wavelength—caustics are hidden at wave bands where absorption and scattering are strong. Planet oblateness induces an asymmetry to the transit light curve about the point of minimum flux, which varies with the planet orientation with respect to the direction of motion. The fractional asymmetry is at the level of 0.5% for a projected oblateness of 10%, independent of whether or not lensing is important. For favorable ratios of planet radius to stellar radius (i.e., gas giant planets), the above effects are potentially observable with future space-based missions. Such measurements could constrain the planet shape and its atmospheric scale height, density, and refractive coefficient, providing information on its rotation, temperature, and composition. We have examined a large range of planetary system parameter space including the planetary scale height and orbital distance. For HD 209458b, the only currently known transiting extrasolar planet, caustics are absent because of the very small lens-source separation (and a large scale height caused by a high temperature from the small separation). Its oblateness is also expected to be small because of the tidal locking of its rotation to orbital motion. Finally, we provide estimates of other variations to transit light curves that could be of comparable importance—including rings, satellites, stellar oscillations, star spots, and weather. Subject headings: gravitational lensing — planetary systems — stars: atmospheres