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Alan P. Boss - One of the best experts on this subject based on the ideXlab platform.
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astrometric constraints on the masses of long period Gas Giant Planets in the trappist 1 planetary system
The Astronomical Journal, 2017Co-Authors: Alan P. Boss, Alycia J. Weinberger, Sandra A. Keiser, Tri L. Astraatmadja, G Angladaescude, Ian B. ThompsonAbstract:Transit photometry of the M8V dwarf star TRAPPIST-1 (2MASS J23062928-0502285) has revealed the presence of at least seven Planets with masses and radii similar to that of Earth, orbiting at distances that might allow liquid water to be present on their surfaces. We have been following TRAPPIST-1 since 2011 with the CAPSCam astrometric camera on the 2.5 m du Pont telescope at the Las Campanas Observatory in Chile. In 2016, we noted that TRAPPIST-1 lies slightly farther away than previously thought, at 12.49 pc, rather than 12.1 pc. Here, we examine 15 epochs of CAPSCam observations of TRAPPIST-1, spanning the five years from 2011 to 2016, and obtain a revised trigonometric distance of 12.56 ± 0.12 pc. The astrometric data analysis pipeline shows no evidence for a long-period astrometric wobble of TRAPPIST-1. After proper motion and parallax are removed, residuals at the level of ±1.3 mas remain. The amplitude of these residuals constrains the masses of any long-period Gas Giant Planets in the TRAPPIST-1 system: no planet more massive than ~4.6 M Jup orbits with a 1 year period, and no planet more massive than ~1.6 M Jup orbits with a 5 year period. Further refinement of the CAPSCam data analysis pipeline, combined with continued CAPSCam observations, should either detect any long-period Planets, or put an even tighter constraint on these mass upper limits.
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Astrometric Constraints on the Masses of Long-Period Gas Giant Planets in the TRAPPIST-1 Planetary System
The Astronomical Journal, 2017Co-Authors: Alan P. Boss, Alycia J. Weinberger, Sandra A. Keiser, Tri L. Astraatmadja, Guillem Anglada-escudé, Ian B. ThompsonAbstract:Transit photometry of the M8V dwarf star TRAPPIST-1 (2MASS J23062928-0502285) has revealed the presence of at least seven Planets with masses and radii similar to that of Earth orbiting at distances that might allow liquid water to be present on their surfaces. We have been following TRAPPIST-1 since 2011 with the CAPSCam astrometric camera on the 2.5-m du Pont telescope at the Las Campanas Observatory in Chile. In 2016 we noted that TRAPPIST-1 lies slightly farther away than previously thought, at 12.49 pc, rather than 12.1 pc. Here we examine fifteen epochs of CAPSCam observations of TRAPPIST-1, spanning the five years from 2011 to 2016, and obtain a revised trigonometric distance of $12.56 \pm 0.12$ pc. The astrometric data analysis pipeline shows no evidence for a long-period astrometric wobble of TRAPPIST-1. After proper motion and parallax are removed, residuals at the level of $\pm 1.3$ millarcsec (mas) remain. The amplitude of these residuals constrains the masses of any long-period Gas Giant Planets in the TRAPPIST-1 system: no planet more massive than $\sim 4.6 M_{Jup}$ orbits with a 1 yr period, and no planet more massive than $\sim 1.6 M_{Jup}$ orbits with a 5 yr period. Further refinement of the CAPSCam data analysis pipeline, combined with continued CAPSCam observations, should either detect any long-period Planets, or put an even tighter constraint on these mass upper limits.
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The Effect of Protoplanetary Disk Cooling Times on the Formation of Gas Giant Planets by Gravitational Instability
The Astrophysical Journal, 2017Co-Authors: Alan P. BossAbstract:Observational evidence exists for the formation of Gas Giant Planets on wide orbits around young stars by disk gravitational instability, but the roles of disk instability and core accretion for forming Gas Giants on shorter period orbits are less clear. The controversy extends to population synthesis models of exoplanet demographics and to hydrodynamical models of the fragmentation process. The latter refers largely to the handling of radiative transfer in three dimensional (3D) hydrodynamical models, which controls heating and cooling processes in gravitationally unstable disks, and hence dense clump formation. A suite of models using the $\beta$ cooling approximation is presented here. The initial disks have masses of 0.091 $M_\odot$ and extend from 4 to 20 AU around a 1 $M_\odot$ protostar. The initial minimum Toomre $Q_i$ values range from 1.3 to 2.7, while $\beta$ ranges from 1 to 100. We show that the choice of $Q_i$ is equal in importance to the $\beta$ value assumed: high $Q_i$ disks can be stable for small $\beta$, when the initial disk temperature is taken as a lower bound, while low $Q_i$ disks can fragment for high $\beta$. These results imply that the evolution of disks toward low $Q_i$ must be taken into account in assessing disk fragmentation possibilities, at least in the inner disk, i.e., inside about 20 AU. The models suggest that if low $Q_i$ disks can form, there should be an as yet largely undetected population of Gas Giants orbiting G dwarfs between about 6 AU and 16 AU.
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Metallicity and Planet Formation: Models
Proceedings of the International Astronomical Union, 2009Co-Authors: Alan P. BossAbstract:Planets typically are considerably more metal-rich than even the most metal-rich stars, one indication that planet formation must differ greatly from star formation. There is general agreement that terrestrial Planets form by the collisional accumulation of solids composed of heavy elements in the inner regions of protoplanetary disks. Two competing mechanisms exist for the formation of Giant Planets, core accretion and disk instability, though hybrid combinations are possible as well. In core accretion, a higher metallicity in the protoplanetary disk leads directly to larger core masses and hence to more Gas Giant Planets. Given the strong correlation of Gas Giant Planets detected by Doppler spectroscopy with stellar metallicity, this has often been taken as proof that core accretion is the mechanism that forms Giant Planets. Recent work, however, implies that the formation of Gas Giants by disk instability can be enhanced by higher metallicities, though not as dramatically as for core accretion. In both scenarios, the ongoing accretion of planetesimals by Gas Giant protoPlanets leads to strong enrichments of heavy elements in their Gaseous envelopes. Both scenarios also imply that Gas Giant Planets should have significant solid cores, raising questions for Gas Giant interior models without cores. ExoPlanets with large inferred core masses seem likely to have formed by core accretion, while Gas Giants at distances beyond 20 AU seem more likely to have formed by disk instability. Given the wide variety of exoPlanets found to date, it appears that both mechanisms are needed to explain the formation of the known population of Giant Planets.
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Observational Tests of Planet Formation Models
Proceedings of the International Astronomical Union, 2007Co-Authors: Alessandro Sozzetti, Alan P. Boss, Guillermo Torres, David W. Latham, Bruce W. Carney, John B. Laird, Robert P. Stefanik, David Charbonneau, Francis T. O'donovan, Matthew J. HolmanAbstract:We summarize the results of two experiments to address important issues related to the correlation between planet frequencies and properties and the metallicity of the hosts. Our results can usefully inform formation, structural, and evolutionary models of Gas Giant Planets.
Douglas N. C. Lin - One of the best experts on this subject based on the ideXlab platform.
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retention of long period Gas Giant Planets type ii migration revisited
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Y B Chen, Douglas N. C. Lin, Xiaojia ZhangAbstract:During their formation, emerging protoPlanets tidally interact with their natal disks. Proto-Gas-Giant Planets, with Hills radius larger than the disk thickness, open gaps and quench Gas flow in the vicinity of their orbits. It is usually assumed that their type II migration is coupled to the viscous evolution of the disk. Although this hypothesis provides an explanation for the origin of close-in Planets, it also encounter predicament on the retention of long-period orbits for most Gas Giant Planets. Moreover, numerical simulations indicate that Planets migrations are not solely determined by the viscous diffusion of their natal disk. Here we carry out a series of hydrodynamic simulations combined with analytic studies to examine the transition between different paradigms of type II migration. We find a range of planetary mass for which Gas continues to flow through a severely depleted gap so that the surface density distribution in the disk region beyond the gap is maintained in a quasi-steady state. The associated gap profile modifies the location of corotation \& Lindblad resonances. In the proximity of the planet's orbit, high-order Lindblad \& corotation torque are weakened by the Gas depletion in the gap while low-order Lindblad torques near the gap walls preserves their magnitude. Consequently, the intrinsic surface density distribution of the disk determines delicately both pace and direction of Planets' type II migration. We show that this effect might stall the inward migration of Giant Planets and preserve them in disk regions where the surface density is steep.
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Transforming Gas Giant Planets into Smaller Objects Through Tidal Disruption
Proceedings of the International Astronomical Union, 2012Co-Authors: Shang-fei Liu, Douglas N. C. Lin, James Guillochon, E. Ramirez-ruizAbstract:AbstractRecent observations have revealed several Jupiter-mass Planets with highly eccentric and / or misaligned orbits, which clearly suggests that dynamical processes operated in these systems. These dynamical processes may result in close encounters between Jupiter-like Planets and their host stars. Using three-dimensional hydrodynamical simulations, we find that Planets with cores are more likely to be retained by their host stars in contrast with previous studies which suggested that coreless Planets are often ejected. We propose that after a long term evolution some Gas Giant Planets could be transformed into super-Earths or Neptune-like Planets, which is supported by our adiabatic evolution models. Finally, we analyze the orbits and structure of known Planets and Kepler candidates and find that our model is capable of producing some of the shortest-period objects.
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DUSTY DISKS AROUND WHITE DWARFS. I. ORIGIN OF DEBRIS DISKS
The Astrophysical Journal, 2010Co-Authors: Ruobing Dong, Douglas N. C. Lin, Yan Wang, X. W. LiuAbstract:A significant fraction of the mature FGK stars have cool dusty disks at least an order of magnitude brighter than the solar system's outer zodiacal light. Since such dusts must be continually replenished, they are generally assumed to be the collisional fragments of residual planetesimals analogous to the Kuiper-Belt objects. At least 10% of solar-type stars also bear Gas Giant Planets. The fraction of stars with known Gas Giants or detectable debris disks (or both) appears to increase with the stellar mass. Here, we examine the dynamical evolution of systems of long-period Gas Giant Planets and residual planetesimals as their host stars evolve off the main sequence, lose mass, and form planetary nebula around remnant white dwarf cores. The orbits of distant Gas Giant Planets and super-km-size planetesimals expand adiabatically. During the most intense asymptotic Giant branch mass-loss phase, sub-meter-size particles migrate toward their host stars due to the strong hydrodynamical drag by the intense stellar wind. Along their migration paths, Gas Giant Planets capture and sweep up sub-km-size planetesimals onto their mean-motion resonances. These planetesimals also acquire modest eccentricities which are determined by the mass of the perturbing Planets, and the rate and speed of stellar mass loss. The swept-up planetesimals undergo disruptive collisions which lead to the production of grains with an extended size range. The radiation drag on these particles is ineffective against the Planets' resonant barrier and they form 30-50 AU size rings which can effectively reprocess the stellar irradiation in the form of FIR continuum. We identify the recently discovered dust ring around the white dwarf WD 2226-210 at the center of the Helix nebula as a prototype of such disks and suggest such rings may be common.
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Planetesimal Accretion onto Growing Proto-Gas Giant Planets
The Astrophysical Journal, 2007Co-Authors: Ji-lin Zhou, Douglas N. C. LinAbstract:The solar and extrasolar Gas Giants appear to have diverse internal structure and metallicities. We examine a potential cause for these dispersions in the context of the conventional sequential accretion formation scenario. In principle, Gas accretion onto cores with masses below several times that of the Earth is suppressed by the energy released from the bombardment of residual planetesimals. Due to their aerodynamical and tidal interaction with the nascent Gas disk, planetesimals on eccentric orbits undergo slow orbital decay. We show that these planetesimals generally cannot pass through the mean motion resonances of the cores, and the suppression of planetesimal bombardment rate enables the cores to accrete Gas with little interruption, thus shortening the timescale of Gas Giant formation. During growth from the cores to protoPlanets, resonances overlap with each other, which strongly enhances the eccentricity excitation of the trapped planetesimals. Subsequent Gas drag induces the planetesimals to migrate to the proximity of the protoPlanets and collide with them. This process leads to the resumption and a surge of planetesimal bombardment during the advanced stage of the protoplanet growth. Intruder planetesimals with different masses can either be resolved in the envelope or reach the core of the protoPlanets. This mechanism may account for the diversity of the core-envelope structure between Jupiter, Saturn, and the metallicity dispersion inferred from the transiting extrasolar Planets. During the final formation stage of the proto-Gas Giants, gap opening in Gas disk leads to the accumulation of planetesimals outside the feeding zone of the protoPlanets. The surface density enhancement promotes the subsequent buildup of cores for secondary Gas Giant Planets outside the orbit of the first-born protoPlanets and the formation of eccentric multiple planet systems.
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Tidal Barrier and the Asymptotic Mass of Proto-Gas Giant Planets
The Astrophysical Journal, 2007Co-Authors: Ian Dobbs-dixon, Douglas N. C. LinAbstract:According to the conventional sequential accretion scenario, observed extrasolar Planets acquired their current masses via efficient Gas accretion onto super-Earth cores with accretion timescales that rapidly increase with mass. Gas accretion in weak-line T Tauri disks may be quenched by global depletion of Gas, but such a mechanism is unlikely to have stalled the growth in planetary systems that contain relatively low-mass, close-in Planets together with more massive, longer period companions. Here, we suggest a potential solution for this conundrum. In general, supersonic infall of surrounding Gas onto a protoplanet is only possible interior to both its Bondi and Roche radii. Above the critical mass where the Roche and Bondi radii are equal to the disk thickness, the protoplanet's tidal perturbation induces the formation of a gap. However, despite continued diffusion into the gap, the azimuthal flux across the protoplanet's Roche lobe will be quenched. Using two different schemes, we present the results of numerical simulations and analysis to show that the accretion rate increases rapidly with the ratio of the protoplanet's Roche to Bondi radii or equivalently to the disk thickness. Gas accretion is quenched, yielding relatively low protoplanetary masses, in regions with low aspect ratios. This becomes important for determining the Gas Giant planet's mass function, the distribution of their masses within multiple-planet systems, and for suppressing the emergence of Gas Giants around low-mass stars. Finally, we find that accretion rates onto protoPlanets declines gradually on a characteristic timescale of a few Myr, during which the protracted accretion timescale onto circumplanetary disks may allow for the formation and retention of regular satellites.
Masahiro N. Machida - One of the best experts on this subject based on the ideXlab platform.
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Gas Accretion onto a Protoplanet and Formation of a Gas Giant Planet
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Masahiro N. Machida, Shu-ichiro Inutsuka, Eiichiro Kokubo, Tomoaki MatsumotoAbstract:We investigate Gas accretion onto a protoplanet, by considering the thermal effect of Gas in three-dimensional hydrodynamical simulations, in which the wide region from a protoplanetary Gas disk to a Jovian radius planet is resolved using the nested-grid method. We estimate the mass accretion rate and growth timescale of Gas Giant Planets. The mass accretion rate increases with protoplanet mass for M_p M_cri, where M_cri = 0.036 M_Jup (a_p/1AU)^0.75, and M_Jup and a_p are the Jovian mass and the orbital radius, respectively. The growth timescale of a Gas Giant planet or the timescale of the Gas accretion onto the protoplanet is about 10^5 yr, that is two orders of magnitude shorter than the growth timescale of the solid core. The thermal effects barely affect the mass accretion rate because the gravitational energy dominates the thermal energy around the protoplanet. The mass accretion rate obtained in our local simulations agrees quantitatively well with those obtained in global simulations with coarser spatial resolution. The mass accretion rate is mainly determined by the protoplanet mass and the property of the protoplanetary disk. We find that the mass accretion rate is correctly calculated when the Hill or Bondi radius is sufficiently resolved. Using the oligarchic growth of protoPlanets, we discuss the formation timescale of Gas Giant Planets.
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Thermal effects of circumplanetary disc formation around proto‐Gas Giant Planets
Monthly Notices of the Royal Astronomical Society, 2009Co-Authors: Masahiro N. MachidaAbstract:The formation of a circumplanetary disc and accretion of angular momentum on to a protoplanetary system are investigated using three-dimensional hydrodynamical simulations. The local region around a protoplanet in a protoplanetary disc is considered with sufficient spatial resolution: the region from outside the Hill sphere to the Jovian radius is covered by the nested-grid method. To investigate the thermal effects of the circumplanetary disc, various equations of state are adopted. Large thermal energy around the protoplanet slightly changes the structure of the circumplanetary disc. Compared with a model adopting an isothermal equation of state, in a model with an adiabatic equation of state, the protoplanet's Gas envelope extends farther, and a slightly thick disc appears near the protoplanet. However, different equations of state do not affect the acquisition process of angular momentum for the protoplanetary system. Thus, the specific angular momentum acquired by the system is fitted as a function only of the protoplanet's mass. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disc. The disc forms only in a compact region in very close proximity to the protoplanet. Adapting the results to the Solar system, the proto-Jupiter and Saturn have compact discs in the region of r < 21r Jup (r < 0.028 r H,Jup ) and r < 66r Sat (r < 0.061r H,sat ), respectively, where r Jup (r H,Jup ) and r Sat (r H.Sat ) are the Jovian and Satumian (Hill) radius, respectively. The surface density has a peak in these regions due to the balance between centrifugal force and gravity of the protoplanet. The size of these discs corresponds well to the outermost orbit of regular satellites around Jupiter and Saturn. Regular satellites may form in such compact discs around proto-Gas Giant Planets.
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thermal effects of circumplanetary disc formation around proto Gas Giant Planets
Monthly Notices of the Royal Astronomical Society, 2009Co-Authors: Masahiro N. MachidaAbstract:The formation of a circumplanetary disc and accretion of angular momentum on to a protoplanetary system are investigated using three-dimensional hydrodynamical simulations. The local region around a protoplanet in a protoplanetary disc is considered with sufficient spatial resolution: the region from outside the Hill sphere to the Jovian radius is covered by the nested-grid method. To investigate the thermal effects of the circumplanetary disc, various equations of state are adopted. Large thermal energy around the protoplanet slightly changes the structure of the circumplanetary disc. Compared with a model adopting an isothermal equation of state, in a model with an adiabatic equation of state, the protoplanet's Gas envelope extends farther, and a slightly thick disc appears near the protoplanet. However, different equations of state do not affect the acquisition process of angular momentum for the protoplanetary system. Thus, the specific angular momentum acquired by the system is fitted as a function only of the protoplanet's mass. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disc. The disc forms only in a compact region in very close proximity to the protoplanet. Adapting the results to the Solar system, the proto-Jupiter and Saturn have compact discs in the region of r < 21r Jup (r < 0.028 r H,Jup ) and r < 66r Sat (r < 0.061r H,sat ), respectively, where r Jup (r H,Jup ) and r Sat (r H.Sat ) are the Jovian and Satumian (Hill) radius, respectively. The surface density has a peak in these regions due to the balance between centrifugal force and gravity of the protoplanet. The size of these discs corresponds well to the outermost orbit of regular satellites around Jupiter and Saturn. Regular satellites may form in such compact discs around proto-Gas Giant Planets.
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Protoplanetary Disk Formation in Molecular Cloud Cores
AIP Conference Proceedings, 2009Co-Authors: Masahiro N. Machida, Shu-ichiro Inutsuka, Tomoaki MatsumotoAbstract:Protoplanetary disk formation is investigated by three‐dimensional hydrodynamic simulations. We directly calculate the disk formation from the molecular cloud core, in which about five orders of magnitude of spatial scale is resolved using a nested grid method. We parameterized the rotational energy of the cloud core, and calculated the disk about ∼105 yr after the protostar formation. After the protoplanetary disk becomes unstable against gravity, fragmentation occurs to form Gas Giant Planets when the cloud core has a larger rotational energy at the initial state. On the other hand, a stable disk maintains for ∼105 yr after the protostar formation when the cloud core has a smaller rotational energy. Comparison of observations with our results indicate that Gas Planets are frequently formed through the gravitational instability in the protoplanetary disk, which possibly accounts for the formation of Gas Giant Planets located far from the central star.
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Thermal Effects of Circumplanetary Disk Formation around Proto-Gas Giant Planets
arXiv: Astrophysics, 2008Co-Authors: Masahiro N. MachidaAbstract:The formation of a circumplanetary disk and accretion of angular momentum onto a protoplanetary system are investigated using 3D hydrodynamical simulations. The local region around a protoplanet in a protoplanetary disk is considered with sufficient spatial resolution: the region from outside the Hill sphere to the Jovian radius is covered by the nested-grid method. To investigate the thermal effects of the circumplanetary disk, various equations of state are adopted. Large thermal energy around the protoplanet slightly changes the structure of the circumplanetary disk. Compared with a model adopting an isothermal equation of state, in a model with an adiabatic equation of state, the protoplanet's Gas envelope extends farther, and a slightly thick disk appears near the protoplanet. However, different equations of state do not affect the acquisition process of angular momentum for the protoplanetary system. Thus, the specific angular momentum acquired by the system is fitted as a function only of the protoplanet's mass. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disk. The disk forms only in a compact region in very close proximity to the protoplanet. Adapting the results to the solar system, the proto-Jupiter and Saturn have compact disks in the region of r < 21 r_J (r < 0.028 r_HJ) and r < 66 r_S (r < 0.061 r_HS), respectively, where r_J (r_HJ) and r_S (r_HS) are the Jovian and Saturnian (Hill) radius, respectively. The surface density has a peak in these regions due to the balance between centrifugal force and gravity of the protoplanet. The size of these disks corresponds well to the outermost orbit of regular satellites around Jupiter and Saturn. Regular satellites may form in such compact disks around proto-Gas Giant Planets.
Heather A Knutson - One of the best experts on this subject based on the ideXlab platform.
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Investigating Trends in Atmospheric Compositions of Cool Gas Giant Planets Using Spitzer Secondary Eclipses
The Astronomical Journal, 2019Co-Authors: Nicole Wallack, Heather A Knutson, Caroline V. Morley, Julianne I. Moses, N. H. Thomas, Daniel Thorngren, Drake Deming, Jean-michel Desert, Jonathan J. Fortney, Joshua A. KammerAbstract:We present new 3.6 and 4.5 μm secondary eclipse measurements for five cool (T 1000 K) transiting Gas Giant Planets: HAT-P-15b, HAT-P-17b, HAT-P-18b, HAT-P-26b, and WASP-69b. We detect eclipses in at least one bandpass for all Planets except HAT-P-15b. We confirm and refine the orbital eccentricity of HAT-P-17b, which is also the only planet in our sample with a known outer companion. We compare our measured eclipse depths in these two bands, which are sensitive to the relative abundances of methane versus carbon monoxide and carbon dioxide, respectively, to predictions from 1D atmosphere models for each planet. For Planets with hydrogen-dominated atmospheres and equilibrium temperatures cooler than ~1000 K, this ratio should vary as a function of both atmospheric metallicity and the carbon-to-oxygen ratio. For HAT-P-26b, our observations are in good agreement with the low atmospheric metallicity inferred from transmission spectroscopy. We find that all four of the Planets with detected eclipses are best matched by models with relatively efficient circulation of energy to the nightside. We see no evidence for a solar-system-like correlation between planet mass and atmospheric metallicity, but instead identify a potential (1.9σ) correlation between the inferred CH₄/(CO + CO₂) ratio and stellar metallicity. Our ability to characterize this potential trend is limited by the relatively large uncertainties in the stellar metallicity values. Our observations provide a first look at the brightness of these Planets at wavelengths accessible to the James Webb Space Telescope, which will be able to resolve individual CH₄, CO, and CO₂ bands and provide much stronger constraints on their atmospheric compositions.
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investigating trends in atmospheric compositions of cool Gas Giant Planets using spitzer secondary eclipses
arXiv: Earth and Planetary Astrophysics, 2019Co-Authors: Nicole Wallack, Heather A Knutson, Caroline V. Morley, Julianne I. Moses, N. H. Thomas, Daniel Thorngren, Drake Deming, Jean-michel Desert, Jonathan J. Fortney, Joshua A. KammerAbstract:We present new 3.6 and 4.5 micron secondary eclipse measurements for five cool (less than approximately 1000 K) transiting Gas Giant Planets: HAT-P-15b, HAT-P-17b, HAT-P-18b, HAT-P-26b, and WASP-69b. We detect eclipses in at least one bandpass for all Planets except HAT-P-15b. We confirm and refine the orbital eccentricity of HAT-P-17b, which is also the only planet in our sample with a known outer companion. We compare our measured eclipse depths in these two bands, which are sensitive to the relative abundances of methane versus carbon monoxide and carbon dioxide, respectively, to predictions from 1D atmosphere models for each planet. For Planets with hydrogen-dominated atmospheres and equilibrium temperatures cooler than approximately 1000 K, this ratio should vary as a function of both atmospheric metallicity and the carbon-to-oxygen ratio. For HAT-P-26b, our observations are in good agreement with the low atmospheric metallicity inferred from transmission spectroscopy. We find that all four of the Planets with detected eclipses are best matched by models with relatively efficient circulation of energy to the nightside. We see no evidence for a solar-system-like correlation between planet mass and atmospheric metallicity, but instead identify a potential (1.9 sigma) correlation between the inferred methane/(carbon monoxide + carbon dioxide) ratio and stellar metallicity. Our ability to characterize this potential trend is limited by the relatively large uncertainties in the stellar metallicity values. Our observations provide a first look at the brightness of these Planets at wavelengths accessible to the James Webb Space Telescope, which will be able to resolve individual methane, carbon monoxide, and carbon dioxide bands and provide much stronger constraints on their atmospheric compositions.
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statistics of long period Gas Giant Planets in known planetary systems
The Astrophysical Journal, 2016Co-Authors: Marta L Bryan, Heather A Knutson, Andrew W Howard, Henry Ngo, Konstantin Batygin, Justin R Crepp, Benjamin J Fulton, Sasha Hinkley, Howard Isaacson, John A JohnsonAbstract:We conducted a Doppler survey at Keck combined with NIRC2 K-band adaptive optics (AO) imaging to search for massive, long-period companions to 123 known exoplanet systems with one or two Planets detected using the radial velocity (RV) method. Our survey is sensitive to Jupiter-mass Planets out to 20 au for a majority of stars in our sample, and we report the discovery of eight new long-period Planets, in addition to 20 systems with statistically significant RV trends that indicate the presence of an outer companion beyond 5 au. We combine our RV observations with AO imaging to determine the range of allowed masses and orbital separations for these companions, and account for variations in our sensitivity to companions among stars in our sample. We estimate the total occurrence rate of companions in our sample to be 52 ± 5% over the range 1–20 M_(Jup) and 5–20 au. Our data also suggest a declining frequency for Gas Giant Planets in these systems beyond 3–10 au, in contrast to earlier studies that found a rising frequency for Giant Planets in the range 0.01–3 au. This suggests either that the frequency of Gas Giant Planets peaks between 3 and 10 au, or that outer companions in these systems have a different semi-major axis distribution than the overall population of Gas Giant Planets. Our results also suggest that hot Gas Giants may be more likely to have an outer companion than cold Gas Giants. We find that Planets with an outer companion have higher average eccentricities than their single counterparts, suggesting that dynamical interactions between Planets may play an important role in these systems.
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Statistics of Long Period Gas Giant Planets in Known Planetary Systems
The Astrophysical Journal, 2016Co-Authors: Marta L Bryan, Heather A Knutson, Andrew W Howard, Henry Ngo, Konstantin Batygin, Justin R Crepp, Benjamin J Fulton, Sasha Hinkley, Howard Isaacson, John A JohnsonAbstract:We conducted a Doppler survey at Keck combined with NIRC2 K-band AO imaging to search for massive, long-period companions to 123 known exoplanet systems with one or two Planets detected using the radial velocity (RV) method. Our survey is sensitive to Jupiter mass Planets out to 20 AU for a majority of stars in our sample, and we report the discovery of eight new long-period Planets, in addition to 20 systems with statistically significant RV trends indicating the presence of an outer companion beyond 5 AU. We combine our RV observations with AO imaging to determine the range of allowed masses and orbital separations for these companions, and account for variations in our sensitivity to companions among stars in our sample. We estimate the total occurrence rate of companions in our sample to be 52 +/- 5% over the range 1 - 20 M_Jup and 5 - 20 AU. Our data also suggest a declining frequency for Gas Giant Planets in these systems beyond 3-10 AU, in contrast to earlier studies that found a rising frequency for Giant Planets in the range 0.01-3 AU. This suggests either that the frequency of Gas Giant Planets peaks between 3-10 AU, or that outer companions in these systems have a different semi-major axis distribution than the overall Gas Giant planet population. Our results also suggest that hot Gas Giants may be more likely to have an outer companion than cold Gas Giants. We find that Planets with an outer companion have higher average eccentricities than their single counterparts, suggesting that dynamical interactions between Planets may play an important role in these systems.
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spitzer secondary eclipse observations of five cool Gas Giant Planets and empirical trends in cool planet emission spectra
The Astrophysical Journal, 2015Co-Authors: Heather A Knutson, Drake Deming, Jonathan J. Fortney, Joshua A. Kammer, Michael R Line, Adam Burrows, Nicolas B Cowan, A H M J Triaud, Eric AgolAbstract:In this work we present Spitzer 3.6 and 4.5 μm secondary eclipse observations of five new cool (<1200 K) transiting Gas Giant Planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for Planets with previously published observations in order to constrain the temperature- and mass-dependent properties of Gas Giant planet atmospheres. We find that the dayside emission spectra of Planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric CH_4/CO ratio to vary as a function of metallicity, and we therefore use our observations of these Planets to constrain their atmospheric metallicities. We find that the most massive Planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller Planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 μm brightness temperatures for these cool transiting Planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these Planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass Planets are more likely to have metal-rich atmospheres.
Joshua A. Kammer - One of the best experts on this subject based on the ideXlab platform.
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Investigating Trends in Atmospheric Compositions of Cool Gas Giant Planets Using Spitzer Secondary Eclipses
The Astronomical Journal, 2019Co-Authors: Nicole Wallack, Heather A Knutson, Caroline V. Morley, Julianne I. Moses, N. H. Thomas, Daniel Thorngren, Drake Deming, Jean-michel Desert, Jonathan J. Fortney, Joshua A. KammerAbstract:We present new 3.6 and 4.5 μm secondary eclipse measurements for five cool (T 1000 K) transiting Gas Giant Planets: HAT-P-15b, HAT-P-17b, HAT-P-18b, HAT-P-26b, and WASP-69b. We detect eclipses in at least one bandpass for all Planets except HAT-P-15b. We confirm and refine the orbital eccentricity of HAT-P-17b, which is also the only planet in our sample with a known outer companion. We compare our measured eclipse depths in these two bands, which are sensitive to the relative abundances of methane versus carbon monoxide and carbon dioxide, respectively, to predictions from 1D atmosphere models for each planet. For Planets with hydrogen-dominated atmospheres and equilibrium temperatures cooler than ~1000 K, this ratio should vary as a function of both atmospheric metallicity and the carbon-to-oxygen ratio. For HAT-P-26b, our observations are in good agreement with the low atmospheric metallicity inferred from transmission spectroscopy. We find that all four of the Planets with detected eclipses are best matched by models with relatively efficient circulation of energy to the nightside. We see no evidence for a solar-system-like correlation between planet mass and atmospheric metallicity, but instead identify a potential (1.9σ) correlation between the inferred CH₄/(CO + CO₂) ratio and stellar metallicity. Our ability to characterize this potential trend is limited by the relatively large uncertainties in the stellar metallicity values. Our observations provide a first look at the brightness of these Planets at wavelengths accessible to the James Webb Space Telescope, which will be able to resolve individual CH₄, CO, and CO₂ bands and provide much stronger constraints on their atmospheric compositions.
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investigating trends in atmospheric compositions of cool Gas Giant Planets using spitzer secondary eclipses
arXiv: Earth and Planetary Astrophysics, 2019Co-Authors: Nicole Wallack, Heather A Knutson, Caroline V. Morley, Julianne I. Moses, N. H. Thomas, Daniel Thorngren, Drake Deming, Jean-michel Desert, Jonathan J. Fortney, Joshua A. KammerAbstract:We present new 3.6 and 4.5 micron secondary eclipse measurements for five cool (less than approximately 1000 K) transiting Gas Giant Planets: HAT-P-15b, HAT-P-17b, HAT-P-18b, HAT-P-26b, and WASP-69b. We detect eclipses in at least one bandpass for all Planets except HAT-P-15b. We confirm and refine the orbital eccentricity of HAT-P-17b, which is also the only planet in our sample with a known outer companion. We compare our measured eclipse depths in these two bands, which are sensitive to the relative abundances of methane versus carbon monoxide and carbon dioxide, respectively, to predictions from 1D atmosphere models for each planet. For Planets with hydrogen-dominated atmospheres and equilibrium temperatures cooler than approximately 1000 K, this ratio should vary as a function of both atmospheric metallicity and the carbon-to-oxygen ratio. For HAT-P-26b, our observations are in good agreement with the low atmospheric metallicity inferred from transmission spectroscopy. We find that all four of the Planets with detected eclipses are best matched by models with relatively efficient circulation of energy to the nightside. We see no evidence for a solar-system-like correlation between planet mass and atmospheric metallicity, but instead identify a potential (1.9 sigma) correlation between the inferred methane/(carbon monoxide + carbon dioxide) ratio and stellar metallicity. Our ability to characterize this potential trend is limited by the relatively large uncertainties in the stellar metallicity values. Our observations provide a first look at the brightness of these Planets at wavelengths accessible to the James Webb Space Telescope, which will be able to resolve individual methane, carbon monoxide, and carbon dioxide bands and provide much stronger constraints on their atmospheric compositions.
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spitzer secondary eclipse observations of five cool Gas Giant Planets and empirical trends in cool planet emission spectra
The Astrophysical Journal, 2015Co-Authors: Heather A Knutson, Drake Deming, Jonathan J. Fortney, Joshua A. Kammer, Michael R Line, Adam Burrows, Nicolas B Cowan, A H M J Triaud, Eric AgolAbstract:In this work we present Spitzer 3.6 and 4.5 μm secondary eclipse observations of five new cool (<1200 K) transiting Gas Giant Planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for Planets with previously published observations in order to constrain the temperature- and mass-dependent properties of Gas Giant planet atmospheres. We find that the dayside emission spectra of Planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric CH_4/CO ratio to vary as a function of metallicity, and we therefore use our observations of these Planets to constrain their atmospheric metallicities. We find that the most massive Planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller Planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 μm brightness temperatures for these cool transiting Planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these Planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass Planets are more likely to have metal-rich atmospheres.
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spitzer secondary eclipse observations of five cool Gas Giant Planets and empirical trends in cool planet emission spectra
arXiv: Earth and Planetary Astrophysics, 2015Co-Authors: Heather A Knutson, Drake Deming, Jonathan J. Fortney, Joshua A. Kammer, Michael R Line, Adam Burrows, Nicolas B Cowan, A H M J Triaud, Eric AgolAbstract:In this work we present Spitzer 3.6 and 4.5 micron secondary eclipse observations of five new cool (<1200 K) transiting Gas Giant Planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for Planets with previously published observations in order to constrain the temperature- and mass-dependent properties of Gas Giant planet atmospheres. We find that the dayside emission spectra of Planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric methane to CO ratio to vary as a function of metallicity, and we therefore use our observations of these Planets to constrain their atmospheric metallicities. We find that the most massive Planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller Planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 micron brightness temperatures for these cool transiting Planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these Planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass Planets are more likely to have metal-rich atmospheres.
