INFLUENCE OF STELLAR MULTIPLICITY ON PLANET FORMATION. III. ADAPTIVE OPTICS IMAGING OFKEPLERSTARS WITH GAS GIANT PLANETS

AbstractWe 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.

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Direct imaging and spectroscopy of planets and brown dwarfs in wide orbits

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311020035 ◽

2010 ◽

Vol 6 (S276) ◽

pp. 113-116

Author(s):

Mariangela Bonavita ◽

Ray Jayawardhana ◽

Markus Janson ◽

David Lafrenière

Keyword(s):

Adaptive Optics ◽

Planet Formation ◽

Giant Planet ◽

Brown Dwarfs ◽

Direct Imaging ◽

Adaptive Optics Imaging ◽

Low Mass ◽

Imaging And Spectroscopy

AbstractRecent direct imaging discoveries of exoplanets have raised new questions about the formation of very low-mass objects in very wide orbits. Several explanations have been proposed, but all of them run into some difficulties, trying to explain all the properties of these objects at once. Here we present the results of a deep adaptive optics imaging survey of 85 stars in the Upper Scorpius young association with Gemini, reaching contrasts of up to 10 magnitudes. In addition to identifying numerous stellar binaries and a few triples, we also found several interesting sub-stellar companions. We discuss the implications of these discoveries, including the possibility of a second pathway to giant planet formation.

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Effect of pebble flux-regulated planetesimal formation on giant planet formation

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038085 ◽

2020 ◽

Vol 642 ◽

pp. A75 ◽

Cited By ~ 6

Author(s):

Oliver Voelkel ◽

Hubert Klahr ◽

Christoph Mordasini ◽

Alexandre Emsenhuber ◽

Christian Lenz

Keyword(s):

Ad Hoc ◽

Planet Formation ◽

Giant Planet ◽

Circumstellar Disks ◽

Giant Planets ◽

Radial Density ◽

Density Distributions ◽

Gas Giant ◽

Self Gravity ◽

Dust Evolution

Context. The formation of gas giant planets by the accretion of 100 km diameter planetesimals is often thought to be inefficient. A diameter of this size is typical for planetesimals and results from self-gravity. Many models therefore use small kilometer-sized planetesimals, or invoke the accretion of pebbles. Furthermore, models based on planetesimal accretion often use the ad hoc assumption of planetesimals that are distributed radially in a minimum-mass solar-nebula way. Aims. We use a dynamical model for planetesimal formation to investigate the effect of various initial radial density distributions on the resulting planet population. In doing so, we highlight the directive role of the early stages of dust evolution into pebbles and planetesimals in the circumstellar disk on the subsequent planet formation. Methods. We implemented a two-population model for solid evolution and a pebble flux-regulated model for planetesimal formation in our global model for planet population synthesis. This framework was used to study the global effect of planetesimal formation on planet formation. As reference, we compared our dynamically formed planetesimal surface densities with ad hoc set distributions of different radial density slopes of planetesimals. Results. Even though required, it is not the total planetesimal disk mass alone, but the planetesimal surface density slope and subsequently the formation mechanism of planetesimals that enables planetary growth through planetesimal accretion. Highly condensed regions of only 100 km sized planetesimals in the inner regions of circumstellar disks can lead to gas giant growth. Conclusions. Pebble flux-regulated planetesimal formation strongly boosts planet formation even when the planetesimals to be accreted are 100 km in size because it is a highly effective mechanism for creating a steep planetesimal density profile. We find that this leads to the formation of giant planets inside 1 au already by pure 100 km planetesimal accretion. Eventually, adding pebble accretion regulated by pebble flux and planetesimal-based embryo formation as well will further complement this picture.

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Constraints on Extrasolar Planet Populations from VLT NACO/SDI and MMT SDI and Direct Adaptive Optics Imaging Surveys: Giant Planets are Rare at Large Separations

The Astrophysical Journal ◽

10.1086/524344 ◽

2008 ◽

Vol 674 (1) ◽

pp. 466-481 ◽

Cited By ~ 64

Author(s):

Eric L. Nielsen ◽

Laird M. Close ◽

Beth A. Biller ◽

Elena Masciadri ◽

Rainer Lenzen

Keyword(s):

Adaptive Optics ◽

Giant Planets ◽

Extrasolar Planet ◽

Adaptive Optics Imaging

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Metallicity and Planet Formation: Models

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310001067 ◽

2009 ◽

Vol 5 (S265) ◽

pp. 391-398

Author(s):

Alan P. Boss

Keyword(s):

Star Formation ◽

Strong Correlation ◽

Planet Formation ◽

Protoplanetary Disks ◽

Giant Planets ◽

Heavy Elements ◽

Doppler Spectroscopy ◽

Gas Giant ◽

Core Accretion ◽

Gaseous Envelopes

AbstractPlanets 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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Dynamical Mass of the Exoplanet Host Star HR 8799

The Astronomical Journal ◽

10.3847/1538-3881/ac3bb5 ◽

2022 ◽

Vol 163 (2) ◽

pp. 52

Author(s):

Aldo G. Sepulveda ◽

Brendan P. Bowler

Keyword(s):

Adaptive Optics ◽

Orbital Motion ◽

Mass Measurement ◽

Massless Particle ◽

Giant Planets ◽

Total System ◽

Keplerian Orbit ◽

Dynamical Mass ◽

Hot Start ◽

Adaptive Optics Imaging

Abstract HR 8799 is a young A5/F0 star hosting four directly imaged giant planets at wide separations (∼16–78 au), which are undergoing orbital motion and have been continuously monitored with adaptive optics imaging since their discovery over a decade ago. We present a dynamical mass of HR 8799 using 130 epochs of relative astrometry of its planets, which include both published measurements and new medium-band 3.1 μm observations that we acquired with NIRC2 at Keck Observatory. For the purpose of measuring the host-star mass, each orbiting planet is treated as a massless particle and is fit with a Keplerian orbit using Markov chain Monte Carlo. We then use a Bayesian framework to combine each independent total mass measurement into a cumulative dynamical mass using all four planets. The dynamical mass of HR 8799 is 1.47 − 0.17 + 0.12 M ⊙ assuming a uniform stellar mass prior, or 1.46 − 0.15 + 0.11 M ⊙ with a weakly informative prior based on spectroscopy. There is a strong covariance between the planets’ eccentricities and the total system mass; when the constraint is limited to low-eccentricity solutions of e < 0.1, which are motivated by dynamical stability, our mass measurement improves to 1.43 − 0.07 + 0.06 M ⊙. Our dynamical mass and other fundamental measured parameters of HR 8799 together with Modules for Experiments in Stellar Astrophysics Isochrones and Stellar Tracks grids yields a bulk metallicity most consistent with [Fe/H] ∼ −0.25–0.00 dex and an age of 10–23 Myr for the system. This implies hot-start masses of 2.7–4.9 M Jup for HR 8799 b and 4.1–7.0 M Jup for HR 8799 c, d, and e, assuming they formed at the same time as the host star.

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Constraints on Extrasolar Planet Populations from VLT NACO/SDI and MMT SDI and Direct Adaptive Optics Imaging Surveys: Giant Planets are Rare at Large Separations

EAS Publications Series ◽

10.1051/eas/1041008 ◽

2010 ◽

Vol 41 ◽

pp. 107-110 ◽

Cited By ~ 2

Author(s):

E. L. Nielsen ◽

L. M. Close ◽

B. A. Biller ◽

E. Masciadri ◽

R. Lenzen

Keyword(s):

Adaptive Optics ◽

Giant Planets ◽

Extrasolar Planet ◽

Adaptive Optics Imaging

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Chemical fingerprints of hot Jupiter planet formation

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732001 ◽

2018 ◽

Vol 612 ◽

pp. A93 ◽

Cited By ~ 12

Author(s):

J. Maldonado ◽

E. Villaver ◽

C. Eiroa

Keyword(s):

Planet Formation ◽

Statistical Tests ◽

Giant Planets ◽

Volatile Elements ◽

Hot Jupiters ◽

Chemical Fingerprints ◽

Gas Giant ◽

Orbital Periods ◽

And Migration

Context. The current paradigm to explain the presence of Jupiter-like planets with small orbital periods (P < 10 days; hot Jupiters), which involves their formation beyond the snow line following inward migration, has been challenged by recent works that explore the possibility of in situ formation. Aims. We aim to test whether stars harbouring hot Jupiters and stars with more distant gas-giant planets show any chemical peculiarity that could be related to different formation processes. Methods. Our methodology is based on the analysis of high-resolution échelle spectra. Stellar parameters and abundances of C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, and Zn for a sample of 88 planet hosts are derived. The sample is divided into stars hosting hot (a < 0.1 au) and cool (a > 0.1 au) Jupiter-like planets. The metallicity and abundance trends of the two sub-samples are compared and set in the context of current models of planet formation and migration. Results. Our results show that stars with hot Jupiters have higher metallicities than stars with cool distant gas-giant planets in the metallicity range +0.00/+0.20 dex. The data also shows a tendency of stars with cool Jupiters to show larger abundances of α elements. No abundance differences between stars with cool and hot Jupiters are found when considering iron peak, volatile elements or the C/O, and Mg/Si ratios. The corresponding p-values from the statistical tests comparing the cumulative distributions of cool and hot planet hosts are 0.20, <0.01, 0.81, and 0.16 for metallicity, α, iron-peak, and volatile elements, respectively. We confirm previous works suggesting that more distant planets show higher planetary masses as well as larger eccentricities. We note differences in age and spectral type between the hot and cool planet host samples that might affect the abundance comparison. Conclusions. The differences in the distribution of planetary mass, period, eccentricity, and stellar host metallicity suggest a different formation mechanism for hot and cool Jupiters. The slightly larger α abundances found in stars harbouring cool Jupiters might compensate their lower metallicities allowing the formation of gas-giant planets.

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Forming terrestrial planets and delivering water

Proceedings of the International Astronomical Union ◽

10.1017/s174392131600572x ◽

2015 ◽

Vol 11 (A29B) ◽

pp. 427-430

Author(s):

Kevin J. Walsh

Keyword(s):

Planet Formation ◽

Semimajor Axis ◽

Giant Planet ◽

Terrestrial Planet ◽

Giant Planets ◽

Asteroid Belt ◽

Terrestrial Planets ◽

The Earth ◽

Building Models ◽

Rich Material

AbstractBuilding models capable of successfully matching the Terrestrial Planet's basic orbital and physical properties has proven difficult. Meanwhile, improved estimates of the nature of water-rich material accreted by the Earth, along with the timing of its delivery, have added even more constraints for models to match. While the outer Asteroid Belt seemingly provides a source for water-rich planetesimals, models that delivered enough of them to the still-forming Terrestrial Planets typically failed on other basic constraints - such as the mass of Mars.Recent models of Terrestrial Planet Formation have explored how the gas-driven migration of the Giant Planets can solve long-standing issues with the Earth/Mars size ratio. This model is forced to reproduce the orbital and taxonomic distribution of bodies in the Asteroid Belt from a much wider range of semimajor axis than previously considered. In doing so, it also provides a mechanism to feed planetesimals from between and beyond the Giant Planet formation region to the still-forming Terrestrial Planets.

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