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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2601.22216 |
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| _version_ | 1866911408522788864 |
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| author | Parker, Richard J. Allen, Megan |
| author_facet | Parker, Richard J. Allen, Megan |
| contents | $λ$ Boötis stars are a subset of chemically peculiar A-stars that display Solar abundances in lighter elements (C, N, O, S, etc.) but a deficiency in Iron-peak elements. This difference has been attributed to the A-stars accreting pristine (metal deficient) gas from the Interstellar Medium. However, the recent discovery of $λ$ Boötis stars in clusters challenges this theory, due to the presence of ionising radiation from intermediate/massive ($>$5 M$_\odot$) stars, which could prevent accretion of pristine ISM gas. We use $N$-body simulations to track the dynamical histories of A-stars during the evolution of a star cluster. We find that some stars leave the confines of the cluster and travel beyond the tidal radius, where they may be able to accrete pristine ISM gas. These A-stars then sometimes move back into the inner regions of the cluster, but the photoionising radiation flux they receive is not high enough to prevent $λ$ Boötis abundances from occurring in these A-stars. We find that A-stars can develop $λ$ Boötis abundances and subsequently form a wide ($>100$ au) binary system, meaning that observations of binary systems that have different abundances between the component stars would not rule out the ISM accretion scenario. Whilst we have shown that $λ$ Boötis stars can reside in and around star clusters, further research is required to assess the validity of the accretion rates required to explain their abundance patterns. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_22216 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Drifters on the edge of town: $λ$ Boötis stars in clusters Parker, Richard J. Allen, Megan Solar and Stellar Astrophysics Astrophysics of Galaxies $λ$ Boötis stars are a subset of chemically peculiar A-stars that display Solar abundances in lighter elements (C, N, O, S, etc.) but a deficiency in Iron-peak elements. This difference has been attributed to the A-stars accreting pristine (metal deficient) gas from the Interstellar Medium. However, the recent discovery of $λ$ Boötis stars in clusters challenges this theory, due to the presence of ionising radiation from intermediate/massive ($>$5 M$_\odot$) stars, which could prevent accretion of pristine ISM gas. We use $N$-body simulations to track the dynamical histories of A-stars during the evolution of a star cluster. We find that some stars leave the confines of the cluster and travel beyond the tidal radius, where they may be able to accrete pristine ISM gas. These A-stars then sometimes move back into the inner regions of the cluster, but the photoionising radiation flux they receive is not high enough to prevent $λ$ Boötis abundances from occurring in these A-stars. We find that A-stars can develop $λ$ Boötis abundances and subsequently form a wide ($>100$ au) binary system, meaning that observations of binary systems that have different abundances between the component stars would not rule out the ISM accretion scenario. Whilst we have shown that $λ$ Boötis stars can reside in and around star clusters, further research is required to assess the validity of the accretion rates required to explain their abundance patterns. |
| title | Drifters on the edge of town: $λ$ Boötis stars in clusters |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2601.22216 |