Exoplanet interior retrievals: core masses and metallicities from atmospheric abundances

Bloot, S.; Miguel, Yamila; Bazot, M.; Howard, Saburo

doi:10.1093/mnras/stad1873

Cited by 4 publications

(1 citation statement)

References 112 publications

(74 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The envelope is assumed to be well mixed and homogeneous throughout, without any compositional gradient in the X, Y, and Z fractions and, therefore, with the same composition as the atmosphere. While the experience on solar system giants tells us that this might not hold true for giant exoplanets (e.g., Mankovich & Fuller 2021;Miguel et al 2022;Bloot et al 2023), a more detailed calculation including compositional gradients is out of the scope of this paper and will be studied in future publications. As initial conditions, we assume the atmosphere to have stellar abundance, which is solar-like for the case of WASP-39 (Mancini et al 2018).…”

Section: Evolution In Mesa and Atmospheric Escape Approachmentioning

confidence: 99%

Metallicity and Spectral Evolution of WASP 39b: The Limited Role of Hydrodynamic Escape

Louca,

Miguel,

Kubyshkina

2023

ApJL

Self Cite

View full text Add to dashboard Cite

The recent observations on WASP-39 b by JWST have revealed hints of high metallicity within the atmosphere compared to its host star. There are various theories on how these high metallic atmospheres emerge. In this study, we closely investigate the impact of extreme escape in the form of hydrodynamic escape to see its impact on atmospheric metallicity and spectral features such as CH4, CO2 and SO2. We perform a grid simulation, with an adapted version of MESA that includes hydrodynamic escape to fully evolve planets with similar masses and radii to the currently observed WASP-39 b estimates. By making use of (photo)chemical kinetics and radiative transfer codes, we evaluate the transmission spectra at various time intervals throughout the simulation. Our results indicate that the massive size of WASP-39 b limits the metal enhancement to a maximum of ∼1.23× the initial metallicity. When incorporating metal drag, this enhancement factor is repressed to an even greater degree, resulting in an enrichment of at most ∼0.4%. As a consequence, when assuming an initial solar metallicity, metal-enriched spectral features like SO2 are still missing after ∼9 Gyr into the simulation. This paper, thus, demonstrates that hydrodynamic escape cannot be the primary process behind the high metallicity observed in the atmosphere of WASP-39 b, suggesting instead that a metal-enhanced atmosphere was established during its formation.

show abstract

Section: Evolution In Mesa and Atmospheric Escape Approachmentioning

confidence: 99%

Metallicity and Spectral Evolution of WASP 39b: The Limited Role of Hydrodynamic Escape

Louca,

Miguel,

Kubyshkina

2023

ApJL

Self Cite

View full text Add to dashboard Cite

show abstract

Enriching inner discs and giant planets with heavy elements

Bitsch,

Mah

2023

A&A

View full text Add to dashboard Cite

Giant exoplanets seem to have on average a much higher heavy-element content than the Solar System giants. Past attempts to explain this heavy-element content include collisions between planets, accretion of volatile rich gas, and accretion of gas enriched in micrometre-sized solids. However, these different theories individually could not explain the heavy-element content of giants and the volatile-to-refractory ratios in the atmospheres of giant planets at the same time. Here we combine the approaches of gas accretion enhanced with vapour and small micrometre-sized dust grains within one model. To this end, we present detailed models of inward-drifting and evaporating pebbles, and describe how these pebbles influence the dust-to-gas ratio and the heavy-element content of the disc. As pebbles drift inwards, the volatile component evaporates and enriches the disc. At the same time, the smaller silicate core of the pebble continues to move inwards. As the silicate pebbles are presumably smaller than the ice grains, they drift more slowly, leading to a pile-up of material inside of the water-ice line, increasing the dust-to-gas ratio in this region. Under the assumption that these small dust grains follow the motion of the gas even through the pressure bumps generated by the gaps between planets, gas accreting giants can accrete large fractions of small solids in addition to the volatile vapour. We find that the effectiveness of the solid enrichment requires a large disc radius to maintain the pebble flux for a long time and a high viscosity that reduces the size and inward drift of the small dust grains. However, this process depends crucially on the debated size difference of the pebbles that are inside and outside of the water-ice line. On the other hand, the volatile component released by the inward-drifting pebbles can lead to a high enrichment with heavy-element vapour, independently of a size difference of pebbles inside and outside the water-ice line. Our model emphasises the importance of the disc’s radius and viscosity to the enrichment of dust and vapour. Consequently, we show how our model could explain the heavy-element content of the majority of giant planets by using combined estimates of dust and vapour enrichment.

show abstract

Composition of giant planets: The roles of pebbles and planetesimals

Danti,

Bitsch,

Mah

2023

A&A

View full text Add to dashboard Cite

One of the current challenges of planet formation theory is to explain the enrichment of observed exoplanetary atmospheres. While past studies have focused on scenarios where either pebbles or planetesimals are the main drivers of heavy element enrichment, here we combine the two approaches to understand whether the composition of a planet can constrain its formation pathway. We study three different formation scenarios: pebble accretion, pebble accretion with planetesimal formation inside the disc, and combined pebble and planetesimal accretion. We used the CHEMCOMP code to perform semi-analytical 1D simulations of protoplanetary discs, including viscous evolution, pebble drift, and simple chemistry to simulate the growth of planets from planetary embryos to gas giants as they migrate through the disc, while simultaneously tracking their composition. Our simulations confirm that the composition of the planetary atmosphere is dominated by the accretion of gas vapour enriched by inward-drifting and evaporating pebbles. Including planetesimal formation hinders this enrichment because many pebbles are locked into planetesimals and cannot evaporate and enrich the disc. This results in a dramatic drop in accreted heavy elements in the cases of planetesimal formation and accretion, demonstrating that planetesimal formation needs to be inefficient in order to explain planets with high heavy element content. On the other hand, accretion of planetesimals enhances the refractory component of the atmosphere, leading to low volatile-to-refractory ratios in the atmosphere, in contrast to the majority of pure pebble simulations. However, low volatile-to-refractory ratios can also be achieved in the pure pebble accretion scenario if the planet migrates all the way into the inner disc and accretes gas that is enriched in evaporated refractories. Distinguishing these two scenarios requires knowledge about the planet’s atmospheric C/H and O/H ratios, which are much higher in the pure pebble scenario compared to the planetesimal formation and accretion scenario. This implies that a detailed knowledge of the composition of planetary atmospheres could help to distinguish between the different formation scenarios.

show abstract

Exoplanet interior retrievals: core masses and metallicities from atmospheric abundances

Cited by 4 publications

References 112 publications

Metallicity and Spectral Evolution of WASP 39b: The Limited Role of Hydrodynamic Escape

Metallicity and Spectral Evolution of WASP 39b: The Limited Role of Hydrodynamic Escape

Enriching inner discs and giant planets with heavy elements

Composition of giant planets: The roles of pebbles and planetesimals

Contact Info

Product

Resources

About