Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants

Abstract

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) $\ge$ 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-$\alpha$ 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 $v_{\text{broad}}\gtrsim 20$ 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 ($\ge 0.05$ 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.

arXiv comment29 pages, 18 figures, 6 tables. Accepted in ApJ

References in corpus (122)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission
• Gaia Data Release 2: The astrometric solution
• The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
• The GALAH Survey: Scientific Motivation
• Gaia Data Release 2: Photometric content and validation
• The GALAH+ Survey: Third Data Release
• The peculiar solar composition and its possible relation to planet formation
• Revised Catalog of GALEX Ultraviolet Sources. I. The All-sky Survey: GUVcat_AIS
• Unresolved stellar companions with Gaia DR2 astrometry
• The Orbital Evolution of Gas Giant Planets around Giant Stars
• Thermohaline instability and rotation-induced mixing. I - Low- and intermediate-mass solar metallicity stars up to the end of the AGB
• High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature
• The accretion of planets and brown dwarfs by giant stars -- II. solar mass stars on the red giant branch
• Gaia Radial Velocity Spectrometer
• Enhanced lithium depletion in Sun-like stars with orbiting planets
• The remarkable solar twin HIP 56948: a prime target in the quest for other Earths
• The Chemical Homogeneity of Sun-like Stars in the Solar Neighborhood
• Lithium depletion in solar-like stars: no planet connection
• The role of binaries in the enrichment of the early Galactic halo. III. Carbon-enhanced metal-poor stars -- CEMP-s stars
• The Accretion of Brown Dwarfs and Planets by Giant Stars -- I. AGB Stars
• Elemental abundance differences in the 16 Cygni binary system: a signature of gas giant planet formation?
• Can Extra Mixing in RGB and AGB Stars Be Attributed to Magnetic Mechanisms?
• Lithium in stars with exoplanets
• The TESS-HERMES survey Data Release 1: high-resolution spectroscopy of the TESS southern continuous viewing zone
• Explosive lithium production in the classical nova V339 Del (Nova Delphini 2013)
• Searching for Young M Dwarfs with GALEX
• Origin of lithium enrichment in K giants
• Li depletion in solar analogues with exoplanets: Extending the sample
• High-precision abundances of elements in solar-type stars. Evidence of two distinct sequences in abundance-age relations
• Optical and X-ray Transients from Planet-Star Mergers
• A path towards understanding the rotation-activity relation of M dwarfs with K2 mission, X-ray and UV data
• Abundances of Stars with Planets: Trends with Condensation Temperature
• On Lithium-Rich Red Giants. I. Engulfment of Sub-Stellar Companions
• Stellar Activity in the Broad-Band Ultraviolet
• Magnetic Mixing in Red Giant and Asymptotic Giant Branch Stars
• Thermohaline mixing in evolved low-mass stars
• Early optical spectra of nova V1369 Cen show presence of Lithium
• Tidal interactions between binary stars drives lithium production in low-mass red giants
• High precision abundances in the 16 Cyg binary system: a signature of the rocky core in the giant planet
• Metal-Poor Lithium-Rich Giants in the Radial Velocity Experiment Survey
• A high precision chemical abundance analysis of the HAT-P-1 stellar binary: constraints on planet formation
• Homogeneous abundance analysis of dwarf, subgiant and giant FGK stars with and without giant planets
• Lithium-Rich Giants in Globular Clusters
• The Curious Case of Elemental Abundance Differences in the Dual Hot Jupiter Hosts WASP-94AB
• Lithium-Rich Field Giants in the Sloan Digital Sky Survey
• Depletion in post-AGB stars with a dusty disc. II
• Rotation and Macroturbulence in Metal-poor Field Red Giant and Red Horizontal Branch Stars
• Discovery of ubiquitous lithium production in low-mass stars
• Lithium-rich giants in the Galactic thick disk
• The nature of the Li enrichment in the most Li-rich giant star
• Highly Enriched 7Be in the ejecta of Nova Sagittarii 2015 No. 2 (V5668 Sgr) and the Galactic Lithium origin
• BD+48 740 - Li overabundant giant star with a planet. A case of recent engulfment?
• Binarity in Cool Asymptotic Giant Branch Stars: A Galex Search for Ultraviolet Excesse
• Three Li-rich K giants: IRAS 12327-6523, IRAS 13539-4153, and IRAS 17596-3952
• Lithium-rich Giants in LAMOST Survey. I. The Catalog
• Most Lithium-rich Low-mass Evolved Stars Revealed as Red Clump stars by Asteroseismology and Spectroscopy
• Chemical evidence for planetary ingestion in a quarter of Sun-like stars
• The s process in AGB stars as constrained by a large sample of Barium stars
• Ultraviolet-Selected Field and Pre-Main-Sequence Stars Towards Taurus and Upper Scorpius
• Parent Stars of Extrasolar Planets. XI. Trends with Condensation Temperature Revisited
• The Gaia-ESO survey: Mixing processes in low-mass stars traced by lithium abundance in cluster and field stars
• Li-rich RGB stars in the Galactic Bulge
• The Solar Twin Planet Search. V. Close-in, low-mass planet candidates and evidence of planet accretion in the solar twin HIP 68468
• Survey of Li-rich giants among Kepler and LAMOST fields: Determination of Li-rich giants Evolutionary Phase
• Detailed Abundances of Stars with Small Planets Discovered by Kepler I: The First Sample
• The Penn State - Torun Centre for Astronomy Planet Search stars. II. Lithium abundance analysis of the Red Giant Clump sample
• Lithium abundances in globular cluster giants: NGC 1904, NGC 2808, and NGC 362
• Enormous Li-enhancement preceding red giant phases in low-mass stars in the Milky Way halo
• The GALAH survey: A census of lithium-rich giant stars
• A helium-flash-induced mixing event can explain the lithium abundances of red clump stars
• Study of Lithium Rich Giants with the GALAH Spectroscopic Survey
• The Super Lithium-Rich Red Giant Rapid Rotator G0928+73.2600: A Case for Planet Accretion?
• Lithium abundances along the RGB: FLAMES-GIRAFFE spectra of a large sample of low-mass Bulge stars
• On Infrared Excesses Associated With Li-Rich K Giants
• Discovery of Super-Li Rich Red Giants in Dwarf Spheroidal Galaxies
• Searching for Li-rich giants in a sample of 12 open clusters: Li enhancement in two stars with substellar companions
• Detailed chemical compositions of planet hosting stars: I. Exploration of possible planet signatures
• Discovery of a super-Li rich turn-off star in the metal poor globular cluster NGC 6397
• The GALAH Survey: A new constraint on cosmological lithium and Galactic lithium evolution from warm dwarf stars
• Barium stars as tracers of s-process nucleosynthesis in AGB stars I. 28 stars with independently derived AGB mass
• Enhancement of Lithium in Red Clump Stars by the Additional Energy Loss Induced by New Physics
• Planet Engulfment Detections are Rare According to Observations and Stellar Modeling
• On Lithium-Rich Red Giants. II. Engulfment on the Giant Branch of Trumpler 20
• Gaia Data Release 3. Stellar chromospheric activity and mass accretion from Ca II IRT observed by the Radial Velocity Spectrometer
• Barium and related stars, and their white-dwarf companions. III. The masses of the white dwarfs
• Planet Engulfment Signatures in Twin Stars
• Rotationally Driven Ultraviolet Emission of Red Giant Stars
• Low-mass lithium-rich AGB stars in the Galactic bulge: evidence for Cool Bottom Processing?
• Chromospheric diagnosis with Ca II lines: forward modeling in forward scattering (I)
• Residual Abundances in GALAH DR3: Implications for Nucleosynthesis and Identification of Unique Stellar Populations
• Extra-Mixing in Luminous Cool Red Giants. Hints from Evolved Stars with and without Li
• On the serendipitous discovery of a Li-rich giant in the globular cluster NGC 362
• The accretion/diffusion theory for lambda Bootis stars in the light of spectroscopic data
• Barium stars as tracers of s-process nucleosynthesis in AGB stars II. Using machine learning techniques on 169 stars
• The Active Chromospheres of Lithium-Rich Red Giant Stars
• Abundance analyses of Li-enriched and normal giants in the GALAH survey
• High-resolution spectroscopic analysis of a large sample of Li-rich giants found by LAMOST
• The formation of barium giants via mass accretion in binary systems
• Mass Matters: No Evidence for Ubiquitous Lithium Production in Low-Mass Clump Giants
• Beryllium Abundances in Stars of One-Solar-Mass
• Statistics of the Chemical Composition of Solar Analog Stars and Links to Planet Formation
• Lithium abundances in giants as a function of stellar mass: An evidence for He-flash as the source of Li enhancement in low mass giants
• The Gaia-ESO Survey: an extremely Li-rich giant in the globular cluster NGC 1261
• Li-rich Giants in LAMOST Survey. III. The statistical analysis of Li-rich giants
• Discovery of s-process enhanced stars in the LAMOST survey
• Lithium abundances and asteroseismology of red giants: understanding the evolution of lithium in giants based on asteroseismic parameters
• Lithium in red giants: the roles of the He-core flash and the luminosity bump
• An unsupervised method for identifying $X$-enriched stars directly from spectra: Li in LAMOST
• Discovery of Nine Super Li-rich Unevolved Stars from the LAMOST Survey
• Lithium in the lower red giant branch of 5 Galactic globular clusters
• Lithium abundances as a tracer of AGB stars pollution in the globular cluster NGC 6752
• Beryllium abundances in turn-off stars of globular clusters with the CUBES spectrograph
• Detecting weak beryllium lines with CUBES
• The behaviour of the excess CaII H & K and H_epsilon emissions in chromospherically active binaries

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• The highest mass Kepler red giants -- II. Spectroscopic parameters, the amplitude-activity relation, and unexpected halo orbits
• Evolution of the ZTF SLRN-2020 star-planet merger