Probing infrared excess connection with Li enhancement among red clump giants

Abstract

We have performed a search among low mass red giants for finding evidence for merger scenario for triggering He-flash and subsequent Li enhancement. We chose a sample of red giants from GALAH survey with well-measured Li abundances, and near and mid-IR fluxes from 2MASS and WISE surveys, respectively. The sample contains 418 cool red clump giants and 359 upper red giant branch giants. Most of the giants and majority of super Li-rich giants show no IR excess. Only five red clump giants and one RGB giant show IR excess. Notably, of the five red clump giants with IR excess, three are super Li-rich (A(Li) > = 3.2 dex), and two are Li-rich (A(Li) > = 1.0 dex). Results suggest Li enhancement among red clump giants may be due to two channels: one resulting from in-situ He-flash in single star evolution and the other due to He-flash triggered by events like merger of He-white dwarfs with giants He-inert core on RGB. In the latter case, IR excess, as a result of mass loss, is expected from merger events. We have modelled IR excess in all six giants using DUSTY code and derived dust parameters. The estimated kinematic ages and time scales of dust envelopes of the super Li-rich phase suggest Li enhancement took place very recently. Further, the analysis shows a significantly higher proportion (four out of five red clump giants) of rapid rotators (vsini > = 8 km/s) among Li-rich giants with IR excess compared to Li-normal and Li-rich giants with no IR excess.

arXiv comment11 pages, 7 figures, 5 tables

References in corpus (37)

• Gaia Data Release 2. Summary of the contents and survey properties
• The GALAH+ Survey: Third Data Release
• Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars
• On the Submillimeter Opacity of Protoplanetary Disks
• Gaia Data Release 2: first stellar parameters from Apsis
• Departures from LTE for neutral Li in late-type stars
• Thermohaline instability and rotation-induced mixing. I - Low- and intermediate-mass solar metallicity stars up to the end of the AGB
• A New Version of Reimers' law of Mass Loss Based on a Physical Approach
• Period spacings in red giants II. Automated measurement
• Rapidly-rotating lithium-rich K giants: The new case of the giant PDS365
• Surface rotation of Kepler red giant stars
• On Lithium-Rich Red Giants. I. Engulfment of Sub-Stellar Companions
• Tidal interactions between binary stars drives lithium production in low-mass red giants
• A newly discovered stellar type: dusty post-red giant branch stars in the Magellanic Clouds
• Discovery of ubiquitous lithium production in low-mass stars
• A large and pristine sample of standard candles across the Milky Way: ~100,000 red clump stars with 3% contamination
• Three Li-rich K giants: IRAS 12327-6523, IRAS 13539-4153, and IRAS 17596-3952
• The Gaia-ESO Survey: Galactic evolution of lithium from iDR6
• The Gaia-ESO survey: Mixing processes in low-mass stars traced by lithium abundance in cluster and field stars
• Survey of Li-rich giants among Kepler and LAMOST fields: Determination of Li-rich giants Evolutionary Phase
• 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
• On Infrared Excesses Associated With Li-Rich K Giants
• White-dwarf red-giant mergers, early-type R stars, J stars and lithium
• Enhancement of Lithium in Red Clump Stars by the Additional Energy Loss Induced by New Physics
• Line Broadening in Field Metal-poor Red Giant and Red Horizontal Branch Stars
• Tracking the evolution of lithium in giants using asteroseismology: Super-Li-rich stars are almost exclusively young red-clump stars
• Far-infrared study of K giants in the solar neighborhood: Connection between Li enrichment and mass-loss
• The Gaia-ESO survey: Lithium abundances in open cluster Red Clump stars
• On the observational characteristics of lithium-enhanced giant stars in comparison with normal red giants
• Extremely red stellar objects revealed by IPHAS
• From the Inner to Outer Milky Way: A Photometric Sample of 2.6 Million Red Clump Stars
• Lithium in Open Cluster Red Giants Hosting Substellar Companions
• Seismic characterization of red giants going through the Helium-core flash
• The GALAH survey: Multiple stars and our Galaxy. I. A comprehensive method for deriving properties of FGK binary stars
• Merged white dwarfs and nucleosynthesis

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