1. Introduction 2. Radial velocities 3. Astrometry 4. Timing 5. Microlensing 6. Transits 7. Imaging 8. Host stars 9. Brown dwarfs and free-floating planets 10. Formation and evolution 11. Interiors and atmospheres 12. The Solar System Appendixes References Index.

/pdf/the-exoplanet-handbook-3g3nzlvc20.pdf

The Exoplanet Handbook

Atmospheric parameters and oxygen abundances of 825 nearby FGK stars are derived using high-quality spectra and a non-local thermodynamic equilibrium analysis of the 777 nm O I triplet lines. We assign a kinematic probability for the stars to be thin-disk (P 1), thick-disk (P 2), and halo (P 3) members. We confirm previous findings of enhanced [O/Fe] in thick-disk (P 2 > 0.5) relative to thin-disk (P 1 > 0.5) stars with [Fe/H] –0.2, as well as a "knee" that connects the mean [O/Fe]-[Fe/H] trend of thick-disk stars with that of thin-disk members at [Fe/H] –0.2. Nevertheless, we find that the kinematic membership criterion fails at separating perfectly the stars in the [O/Fe]-[Fe/H] plane, even when a very restrictive kinematic separation is employed. Stars with "intermediate" kinematics (P 1 0.5) show a large star-to-star scatter in [O/Fe]-[Fe/H], but most of it is due to stars with Galactocentric rotational velocity V –200 km s–1 follow an [O/Fe]-[Fe/H] relation with almost no star-to-star scatter. Early mergers with satellite galaxies explain most of our observations, but the significant fraction of disk stars with "ambiguous" kinematics and abundances suggests that scattering by molecular clouds and radial migration have both played an important role in determining the kinematic and chemical properties of solar neighborhood stars.

/pdf/oxygen-abundances-in-nearby-fgk-stars-and-the-galactic-2cnhfrrqpi.pdf

Oxygen abundances in nearby fgk stars and the galactic chemical evolution of the local disk and halo

Spitzer Space Telescope and Herschel Space Observatory imaging of M31 is used, with a physical dust model, to construct maps of dust surface density, dust-to-gas ratio, starlight heating intensity, and polycyclic aromatic hydrocarbon (PAH) abundance, out to R ≈ 25 kpc. The global dust mass is M {sub d} = 5.4 × 10{sup 7} M {sub ☉}, the global dust/H mass ratio is M {sub d}/M {sub H} = 0.0081, and the global PAH abundance is (q {sub PAH}) = 0.039. The dust surface density has an inner ring at R = 5.6 kpc, a maximum at R = 11.2 kpc, and an outer ring at R ≈ 15.1 kpc. The dust/gas ratio varies from M {sub d}/M {sub H} ≈ 0.026 at the center to ∼0.0027 at R ≈ 25 kpc. From the dust/gas ratio, we estimate the interstellar medium metallicity to vary by a factor ∼10, from Z/Z {sub ☉} ≈ 3 at R = 0 to ∼0.3 at R = 25 kpc. The dust heating rate parameter (U) peaks at the center, with (U) ≈ 35, declining to (U) ≈ 0.25 at R = 20 kpc. Within the central kiloparsec, the starlight heating intensity inferred from themore » dust modeling is close to what is estimated from the stars in the bulge. The PAH abundance reaches a peak q {sub PAH} ≈ 0.045 at R ≈ 11.2 kpc. When allowance is made for the different spectrum of the bulge stars, q {sub PAH} for the dust in the central kiloparsec is similar to the overall value of q {sub PAH} in the disk. The silicate-graphite-PAH dust model used here is generally able to reproduce the observed dust spectral energy distribution across M31, but overpredicts 500 μm emission at R ≈ 2-6 kpc, suggesting that at R = 2-6 kpc, the dust opacity varies more steeply with frequency (with β ≈ 2.3 between 200 and 600 μm) than in the model.« less

http://iopscience.iop.org/article/10.1088/0004-637X/780/2/172/pdf

Andromeda's dust

PLANETARY SYSTEMS, the solar system amongst them, are believed to form as inevitable and common byproducts of star formation For orientation, an overview of the processes described in this chapter is as follows The present paradigm starts with star formation in molecular clouds Brown dwarfs are formed as the lowmass tail of this process, although some may be formed as a high-mass tail of planet formation Gas and dust in the collapsing molecular cloud which does not fall directly onto the protostar resides in a relatively long-lived accretion disk which provides the environment for the subsequent stages of planet formation Terrestrial-mass planets are formed within the disk through the progressive agglomeration of material denoted, as it grows in size, as dust, rocks, planetesimals and protoplanets A similar process typically occurring further out in the disk results in the cores of giant planets, which then gravitationally accumulate their mantles of ice and/or gas As the planet-forming bodies grow in mass, growth and dynamics become more dominated by gravitational interactions Towards the final phases, and before the remaining gas is lost through accretion or dispersal, the gas provides a viscous medium at least partially responsible for planetary migration Some migration also occurs during these later stages as a result of gravitational scattering between the (proto-)planets and the residual sea of planetesimals The final structural stabilisation of the planetary system may be affected by planet–planet interactions, until a configuration emerges which may be dynamically stable over billions of years The current observational data for exoplanet systems is broadly compatible with this overall picture Other constraints come from a substantial body of detailed observations of the solar system (Chapter 12) Context and present paradigm An understanding of howplanets formis essential in understanding and interpreting the considerable range of observed planetary system architectures and dynamics Today, the most widely considered solar nebula theory holds that planet formation in the solar system, and by inference in other exoplanet systems, follows on from the process of star formation and accretion disk formation, through the agglomeration of residual material as the protoplanetary disk collapses and evolves

The Exoplanet Handbook: Formation and evolution

© 2021 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1093/mnras/stab1242

/pdf/the-galah-survey-third-data-release-2r8esvv4hi.pdf

The GALAH+ survey: Third data release

We derive atmospheric parameters and lithium abundances for 671 stars and include our measurements in a literature compilation of 1381 dwarf and subgiant stars. First, a lithium desert in the effective temperature (T eff) versus lithium abundance (A Li) plane is observed such that no stars with T eff 6075?K and A Li 1.8 are found. We speculate that most of the stars on the low A Li side of the desert have experienced a short-lived period of severe surface lithium destruction as main-sequence or subgiant stars. Next, we search for differences in the lithium content of thin-disk and thick-disk stars, but we find that internal processes have erased from the stellar photospheres their possibly different histories of lithium enrichment. Nevertheless, we note that the maximum lithium abundance of thick-disk stars is nearly constant from [Fe/H] = ?1.0 to ?0.1, at a value that is similar to that measured in very metal-poor halo stars (A Li 2.2). Finally, differences in the lithium abundance distribution of known planet-host stars relative to otherwise ordinary stars appear when restricting the samples to narrow ranges of T eff or mass, but they are fully explained by age and metallicity biases. We confirm the lack of a connection between low lithium abundance and planets. However, we find that no low A Li planet-hosts are found in the desert T eff window. Provided that subtle sample biases are not responsible for this observation, this suggests that the presence of gas giant planets inhibit the mechanism responsible for the lithium desert.

/pdf/lithium-abundances-in-nearby-fgk-dwarf-and-subgiant-stars-2hs41yiejc.pdf

Lithium abundances in nearby fgk dwarf and subgiant stars: internal destruction, galactic chemical evolution, and exoplanets

The atmospheric parameters of the components of the 16 Cygni binary system, in which the secondary has a gas giant planet detected, are measured accurately using high-quality observational data. Abundances relative to solar are obtained for 25 elements with a mean error of σ([X/H]) = 0.023 dex. The fact that 16 Cyg A has about four times more lithium than 16 Cyg B is normal considering the slightly different masses of the stars. The abundance patterns of 16 Cyg A and B, relative to iron, are typical of that observed in most of the so-called solar twin stars, with the exception of the heavy elements (Z > 30), which can, however, be explained by Galactic chemical evolution. Differential (A-B) abundances are measured with even higher precision (σ(Δ[X/H]) = 0.018 dex, on average). We find that 16 Cyg A is more metal-rich than 16 Cyg B by Δ[M/H] = +0.041 ± 0.007 dex. On an element-to-element basis, no correlation between the A-B abundance differences and dust condensation temperature (T C) is detected. Based on these results, we conclude that if the process of planet formation around 16 Cyg B is responsible for the observed abundance pattern, the formation of gas giants produces a constant downward shift in the photospheric abundance of metals, without a T C correlation. The latter would be produced by the formation of terrestrial planets instead, as suggested by other recent works on precise elemental abundances. Nevertheless, a scenario consistent with these observations requires the convective envelopes of 1 M ☉ stars to reach their present-day sizes about three times quicker than predicted by standard stellar evolution models.

http://iopscience.iop.org/article/10.1088/0004-637X/740/2/76/pdf

Elemental abundance differences in the 16 Cygni binary system: A signature of gas giant planet formation?

We derive atmospheric parameters and lithium abundances for 671 stars and include our measurements in a literature compilation of 1381 dwarf and subgiant stars. First, a "lithium desert" in the effective temperature (Teff) versus lithium abundance (A_Li) plane is observed such that no stars with Teff~6075 K and A_Li~1.8 are found. We speculate that most of the stars on the low A_Li side of the desert have experienced a short-lived period of severe surface lithium destruction as main-sequence or subgiant stars. Next, we search for differences in the lithium content of thin-disk and thick-disk stars, but we find that internal processes have erased from the stellar photospheres their possibly different histories of lithium enrichment. Nevertheless, we note that the maximum lithium abundance of thick-disk stars is nearly constant from [Fe/H]=-1.0 to -0.1, at a value that is similar to that measured in very metal-poor halo stars (A_Li~2.2). Finally, differences in the lithium abundance distribution of known planet-host stars relative to otherwise ordinary stars appear when restricting the samples to narrow ranges of Teff or mass, but they are fully explained by age and metallicity biases. We confirm the lack of a connection between low lithium abundance and planets. However, we find that no low A_Li planet-hosts are found in the desert Teff window. Provided that subtle sample biases are not responsible for this observation, this suggests that the presence of gas giant planets inhibit the mechanism responsible for the lithium desert.

/pdf/lithium-abundances-in-nearby-fgk-dwarf-and-subgiant-stars-zrdlnuk2uz.pdf

Lithium abundances in nearby FGK dwarf and subgiant stars: internal destruction, Galactic chemical evolution, and exoplanets

The atmospheric parameters of the components of the 16Cygni binary system, in which the secondary has a gas giant planet detected, are measured accurately using high quality observational data. Abundances relative to solar are obtained for 25 elements with a mean error of 0.023 dex. The fact that 16CygA has about four times more lithium than 16CygB is normal considering the slightly different masses of the stars. The abundance patterns of 16CygA and B, relative to iron, are typical of that observed in most of the so-called solar twin stars, with the exception of the heavy elements (Z>30), which can, however, be explained by Galactic chemical evolution. Differential (A-B) abundances are measured with even higher precision (0.018 dex, on average). We find that 16CygA is more metal-rich than 16CygB by 0.041+/-0.007 dex. On an element-to-element basis, no correlation between the A-B abundance differences and dust condensation temperature (Tc) is detected. Based on these results, we conclude that if the process of planet formation around 16CygB is responsible for the observed abundance pattern, the formation of gas giants produces a constant downwards shift in the photospheric abundance of metals, without a Tc correlation. The latter would be produced by the formation of terrestrial planets instead, as suggested by other recent works on precise elemental abundances. Nevertheless, a scenario consistent with these observations requires the convective envelopes of 1 Msun stars to reach their present-day sizes about three times quicker than predicted by standard stellar evolution models.

J. R. Fish

Papers

Lithium abundances in nearby fgk dwarf and subgiant stars: internal destruction, galactic chemical evolution, and exoplanets

Elemental abundance differences in the 16 Cygni binary system: A signature of gas giant planet formation?

Lithium abundances in nearby FGK dwarf and subgiant stars: internal destruction, Galactic chemical evolution, and exoplanets

Elemental abundance differences in the 16 Cygni binary system: a signature of gas giant planet formation?