Insight into the Formation of β Pic b through the Composition of Its Parent Protoplanetary Disk as Revealed by the β Pic Moving Group Member HD 181327

It has been suggested that β Pic b has a supersolar metallicity and subsolar C/O ratio. Assuming solar carbon and oxygen abundances for the star β Pic and therefore the planet’s parent protoplanetary disk, β Pic b’s C/O ratio suggests that it formed via core accretion between its parent protoplaneta...

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Published in:The Astronomical journal Vol. 167; no. 1; pp. 45 - 56
Main Authors: Reggiani, Henrique, Galarza, Jhon Yana, Schlaufman, Kevin C., Sing, David K., Healy, Brian F., McWilliam, Andrew, Lothringer, Joshua D., Pueyo, Laurent
Format: Journal Article
Language:English
Published: Madison The American Astronomical Society 01.01.2024
IOP Publishing
Subjects:
Abundance
Astrochemistry
Carbon
Carbon dioxide
Composition
Deposition
Exoplanet astronomy
Exoplanet atmospheres
Exoplanet atmospheric composition
Exoplanet formation
Exoplanet migration
Exoplanet systems
Massive stars
Metallicity
Molecular clouds
Oxygen
Photosphere
Planet formation
Planet hosting stars
Protoplanetary disks
Stars
Stellar abundances
ISSN:0004-6256, 1538-3881
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Summary:It has been suggested that β Pic b has a supersolar metallicity and subsolar C/O ratio. Assuming solar carbon and oxygen abundances for the star β Pic and therefore the planet’s parent protoplanetary disk, β Pic b’s C/O ratio suggests that it formed via core accretion between its parent protoplanetary disk’s H 2 O and CO 2 ice lines. However, β Pic b’s high metallicity is difficult to reconcile with its mass M p = 11.7 M Jup . Massive stars can present peculiar photospheric abundances that are unlikely to record the abundances of their former protoplanetary disks. This issue can be overcome for early-type stars in moving groups by inferring the elemental abundances of the FGK stars in the same moving group that formed in the same molecular cloud and presumably share the same composition. We infer the photospheric abundances of the F dwarf HD 181327, a β Pic moving group member that is the best available proxy for the composition of β Pic b’s parent protoplanetary disk. In parallel, we infer updated atmospheric abundances for β Pic b. As expected for a planet of its mass formed via core-accretion beyond its parent protoplanetary disk’s H 2 O ice line, we find that β Pic b’s atmosphere is consistent with stellar metallicity and confirm that it has superstellar carbon and oxygen abundances with a substellar C/O ratio. We propose that the elemental abundances of FGK dwarfs in moving groups can be used as proxies for the otherwise difficult-to-infer elemental abundances of early-type and late-type members of the same moving groups.
Bibliography:AAS49058
The Solar System, Exoplanets, and Astrobiology
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ISSN:0004-6256
1538-3881
DOI:10.3847/1538-3881/ad0f93