Early Accretion of Large Amounts of Solids for Directly-Imaged Exoplanets
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866915140439375872 |
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| author | Wang, Ji |
| author_facet | Wang, Ji |
| contents | As the number of planetary mass objects (PMOs, $\lessapprox$13 M$_{\rm{Jupiter}}$) at wider separation ($\gtrapprox$10 AU) grows, there is emerging evidence that they form differently from their higher-mass brown-dwarf (BD) counterparts. Specifically, PMOs' atmospheres are often enriched by metals and show a large dispersion of metallicity, which is usually interpreted as a sign of solid accretion. {As a first step toward a population-level study of the amount and timing of solid accretion, }we analyze a sample of seven directly-imaged exoplanets with measured stellar and planetary chemical abundances (51 Eri b, $β$ Pic b, HIP 65426 b, HR 8799 c and e, AF Lep b, and YSES 1 c). Our analysis uses existing data of stellar and planetary atmospheric metallicities, and adopts a Bayesian framework that marginalizes the probabilities of disk conditions, formation locations, {planetary interior structures}, and accretion physics. We show that these PMOs accrete large amounts of solids {regardless of whether they form via core accretion or disk instability}. On average $\gtrapprox$50 M$_\oplus$ solids are accreted to enrich planet atmospheres. {Individual planet accretes between 23.3 and 223.2 M$_\oplus$ of solid mass, more than 75\% of which is assumed to stay in the atmosphere and increase the observed metallicity.} The result implies that the solid accretion process and therefore the planet formation process {likely take place} at an early stage {($\lessapprox$2 Myr)} when large amounts of solids are available in young {massive} protoplanetary disks. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2310_00088 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Early Accretion of Large Amounts of Solids for Directly-Imaged Exoplanets Wang, Ji Earth and Planetary Astrophysics Solar and Stellar Astrophysics As the number of planetary mass objects (PMOs, $\lessapprox$13 M$_{\rm{Jupiter}}$) at wider separation ($\gtrapprox$10 AU) grows, there is emerging evidence that they form differently from their higher-mass brown-dwarf (BD) counterparts. Specifically, PMOs' atmospheres are often enriched by metals and show a large dispersion of metallicity, which is usually interpreted as a sign of solid accretion. {As a first step toward a population-level study of the amount and timing of solid accretion, }we analyze a sample of seven directly-imaged exoplanets with measured stellar and planetary chemical abundances (51 Eri b, $β$ Pic b, HIP 65426 b, HR 8799 c and e, AF Lep b, and YSES 1 c). Our analysis uses existing data of stellar and planetary atmospheric metallicities, and adopts a Bayesian framework that marginalizes the probabilities of disk conditions, formation locations, {planetary interior structures}, and accretion physics. We show that these PMOs accrete large amounts of solids {regardless of whether they form via core accretion or disk instability}. On average $\gtrapprox$50 M$_\oplus$ solids are accreted to enrich planet atmospheres. {Individual planet accretes between 23.3 and 223.2 M$_\oplus$ of solid mass, more than 75\% of which is assumed to stay in the atmosphere and increase the observed metallicity.} The result implies that the solid accretion process and therefore the planet formation process {likely take place} at an early stage {($\lessapprox$2 Myr)} when large amounts of solids are available in young {massive} protoplanetary disks. |
| title | Early Accretion of Large Amounts of Solids for Directly-Imaged Exoplanets |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2310.00088 |