Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants
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| Autores principales: | , , , , , , , , , , |
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| Formato: | Preprint |
| Publicado: |
2023
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| _version_ | 1866912201398288384 |
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| author | Sayeed, Maryum Ness, Melissa K. Montet, Benjamin T. Cantiello, Matteo Casey, Andrew R. Buder, Sven Bedell, Megan Breivik, Katelyn Metzger, Brian D. Martell, Sarah L. McGee-Gold, Leah |
| author_facet | Sayeed, Maryum Ness, Melissa K. Montet, Benjamin T. Cantiello, Matteo Casey, Andrew R. Buder, Sven Bedell, Megan Breivik, Katelyn Metzger, Brian D. Martell, Sarah L. McGee-Gold, Leah |
| contents | Stellar models predict that lithium (Li) inside a star is destroyed during the first dredge-up phase, yet 1.2% of red giant stars are Li-rich. We aim to uncover possible origins of this population, by analysing 1155 Li-rich giants (A(Li) $\geq$ 1.5) in GALAH DR3. To expose peculiar traits of Li-rich stars, we construct a reference sample of Li-normal (doppelgänger) stars with matched evolutionary state and fiducial supernova abundances. Comparing Li-rich and doppelgänger spectra reveals systematic differences in the H-$α$ and Ca-triplet line profiles associated with the velocity broadening measurement. We also find twice as many Li-rich stars appear to be fast rotators (2% with $v_\textrm{broad} \gtrsim 20$ km s$^{-1}$) compared to doppelgängers. On average, Li-rich stars have higher abundances than their doppelgängers, for a subset of elements, and Li-rich stars at the base of RGB have higher mean $s-$process abundances ($\geq 0.05$ dex for Ba, Y, Zr), relative to their doppelgängers. External mass-transfer from intermediate-mass AGB companions could explain this signature. Additional companion analysis excludes binaries with mass ratios $\gtrsim$ 0.5 at $\gtrsim$ 7 AU. We also discover that highly Ba-enriched stars are missing from the Li-rich population, possibly due to low-mass AGB companions which preclude Li-enrichment. Finally, we confirm a prevalence of Li-rich stars on the red clump that increases with lithium, which supports an evolutionary state mechanism for Li-enhancement. Multiple culprits, including binary spin-up and mass-transfer, are therefore likely mechanisms of Li-enrichment. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2306_03323 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants Sayeed, Maryum Ness, Melissa K. Montet, Benjamin T. Cantiello, Matteo Casey, Andrew R. Buder, Sven Bedell, Megan Breivik, Katelyn Metzger, Brian D. Martell, Sarah L. McGee-Gold, Leah Solar and Stellar Astrophysics Astrophysics of Galaxies Stellar models predict that lithium (Li) inside a star is destroyed during the first dredge-up phase, yet 1.2% of red giant stars are Li-rich. We aim to uncover possible origins of this population, by analysing 1155 Li-rich giants (A(Li) $\geq$ 1.5) in GALAH DR3. To expose peculiar traits of Li-rich stars, we construct a reference sample of Li-normal (doppelgänger) stars with matched evolutionary state and fiducial supernova abundances. Comparing Li-rich and doppelgänger spectra reveals systematic differences in the H-$α$ and Ca-triplet line profiles associated with the velocity broadening measurement. We also find twice as many Li-rich stars appear to be fast rotators (2% with $v_\textrm{broad} \gtrsim 20$ km s$^{-1}$) compared to doppelgängers. On average, Li-rich stars have higher abundances than their doppelgängers, for a subset of elements, and Li-rich stars at the base of RGB have higher mean $s-$process abundances ($\geq 0.05$ dex for Ba, Y, Zr), relative to their doppelgängers. External mass-transfer from intermediate-mass AGB companions could explain this signature. Additional companion analysis excludes binaries with mass ratios $\gtrsim$ 0.5 at $\gtrsim$ 7 AU. We also discover that highly Ba-enriched stars are missing from the Li-rich population, possibly due to low-mass AGB companions which preclude Li-enrichment. Finally, we confirm a prevalence of Li-rich stars on the red clump that increases with lithium, which supports an evolutionary state mechanism for Li-enhancement. Multiple culprits, including binary spin-up and mass-transfer, are therefore likely mechanisms of Li-enrichment. |
| title | Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2306.03323 |