Lithium-rich M-dwarfs at the ZAMS: Evidence for planetary engulfment?
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866911715958980608 |
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| author | Jeffries, R. D. Jackson, R. J. Baraffe, I. |
| author_facet | Jeffries, R. D. Jackson, R. J. Baraffe, I. |
| contents | We identify 6 early M-dwarfs, in 3 open clusters (NGC 2451a, Blanco 1 and NGC 2516) at ages of 50-200 Myr, that are anomalously enriched in lithium compared with Li-depleted siblings of similar spectral type. The Li-rich outliers represent 2-3 per cent of stars with $3560 < T_{\rm eff}/{\rm K} < 4045$ in clusters at those ages but are otherwise indistinguishable in their positions, parallaxes and kinematics from other cluster members; their placement in absolute colour-magnitude diagrams is incompatible with being much younger Li-rich interlopers, only one shows evidence of binarity and they are all slow rotators. The enhanced Li abundances are consistent with the engulfment of 3-10 $M_\oplus$ of volatile-depleted planetary material after the formation of a radiative core has ended rapid pre main sequence Li depletion. Published planetary formation simulations featuring engulfment via dynamical interactions, and the preponderance of Earth-like exoplanets in close orbits around M-dwarfs, offer some support to this scenario. The observed occurrence rate would be a lower limit to the frequency with which such engulfment events occur between ages of $\sim (30-200)$ Myr, that depends in the timescale for ongoing Li depletion at the ZAMS. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_25747 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Lithium-rich M-dwarfs at the ZAMS: Evidence for planetary engulfment? Jeffries, R. D. Jackson, R. J. Baraffe, I. Solar and Stellar Astrophysics Earth and Planetary Astrophysics We identify 6 early M-dwarfs, in 3 open clusters (NGC 2451a, Blanco 1 and NGC 2516) at ages of 50-200 Myr, that are anomalously enriched in lithium compared with Li-depleted siblings of similar spectral type. The Li-rich outliers represent 2-3 per cent of stars with $3560 < T_{\rm eff}/{\rm K} < 4045$ in clusters at those ages but are otherwise indistinguishable in their positions, parallaxes and kinematics from other cluster members; their placement in absolute colour-magnitude diagrams is incompatible with being much younger Li-rich interlopers, only one shows evidence of binarity and they are all slow rotators. The enhanced Li abundances are consistent with the engulfment of 3-10 $M_\oplus$ of volatile-depleted planetary material after the formation of a radiative core has ended rapid pre main sequence Li depletion. Published planetary formation simulations featuring engulfment via dynamical interactions, and the preponderance of Earth-like exoplanets in close orbits around M-dwarfs, offer some support to this scenario. The observed occurrence rate would be a lower limit to the frequency with which such engulfment events occur between ages of $\sim (30-200)$ Myr, that depends in the timescale for ongoing Li depletion at the ZAMS. |
| title | Lithium-rich M-dwarfs at the ZAMS: Evidence for planetary engulfment? |
| topic | Solar and Stellar Astrophysics Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2605.25747 |