The<i>Gaia</i>-ESO Survey: revisiting the Li-rich giant problem

Casey, Andrew R.; Ruchti, G.; Masseron, T.; Randich, S.; Gilmore, G.; Lind, Karin; Kennedy, Grant M.; Koposov, S. E.; Hourihane, A.; Franciosini, E.; Lewis, Jim; Magrini, L.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.; Feltzing, Sofia; Jeffries, R. D.; Vallenari, A.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; François, P.; Korn, A. J.; Lanzafame, A. C.; Pancino, E.; Recio–Blanco, A.; Smiljanić, R.; Carraro, G.; Costado, M. T.; Damiani, F.; Donati, P.; Frasca, A.; Jofré, P.; Lardo, C.; Laverny, P. de; Monaco, L.; Prisinzano, L.; Sbordone, L.; Sousa, S. G.; Tautvaišienė, G.; Zaggia, S.; Zwitter, T.; Delgado-Mena, E.; Chorniy, Y.; Martell, Sarah L.; Aguirre, V. Silva; Miglio, A.; Chiappini, Cristina; Montalbán, J.; Morel, Thierry; Valentini, M.

doi:10.1093/mnras/stw1512

Cited by 83 publications

(86 citation statements)

References 128 publications

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“…Our sample of Li-rich giants is not s-process enriched. The Gaia-ESO survey of Li-rich giants (Casey et al 2016;Smiljanic et al 2018) has provided information on the compositions of a few giants indicating essentially normal compositions relative to normal giants.…”

Section: Discussionmentioning

confidence: 99%

Abundance analyses of Li-enriched and normal giants in the GALAH survey

Deepak

Lambert

Reddy

2020

Monthly Notices of the Royal Astronomical Society

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Compositions of lithium-enriched and normal giants among the GALAH survey are compared. Except for Li, the only detectable abundance difference between lithiumenriched and normal giants among the investigated elements from carbon to europium occurs for carbon. Among Li-rich giants with A(Li) = 1.8 to 3.1, the C deficiency is very similar to that reported for the normal giants (with A(Li) < 1.8) where the slight C deficiency arises from the first dredge-up. Carbon is slightly under abundant relative to normal giants among the super Li-rich giants where the Li abundance exceeds A(Li) = 3.2. The C abundance as well as the 12 C/ 13 C ratios from the literature suggest that addition of Li to create a Li-rich giant may occur independently of the abundance changes wrought by the first dredge-up. Creation of a super Li-rich giant, however, appears to occur with additional CN-cycle conversion of C to N. The probability of becoming a Li-rich giant is approximately independent of a star's mass, although the majority of the Li-rich giants are found to be low mass (M ≤ 2 M ). The frequency of occurrence of Li-enriched giants among normal giants is about one percent and slightly dependent on metallicity ([Fe/H]). Li-enriched and normal giants are found to have similar projected rotational velocity which suggest that Li-enrichment in giants is not linked to scenarios such as mergers and tidal interaction between binary stars.

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Section: Discussionmentioning

confidence: 99%

Abundance analyses of Li-enriched and normal giants in the GALAH survey

Deepak

Lambert

Reddy

2020

Monthly Notices of the Royal Astronomical Society

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“…The list of our program stars (20 Li-rich giants; most of them are apparently bright as V < ∼ 8 mag) is presented in table 1, which were selected from the compilation of Casey et al (2016;cf. Kumar, Reddy, and Lambert's (2011) paper is important, since 16 stars (out of 20) are included in their study, which may be referenced for the properties not touched in this paper (e.g., 12 C/ 13 C ratio). The spectroscopic observations of these targets were carried out by using the High Dispersion Spectrograph (HDS; Noguchi et al 2002) placed at the Nasmyth platform of the 8.2-m Subaru Telescope on 2016 October 12-13 (UT; two first half-nights).…”

Section: Observational Datamentioning

confidence: 99%

“…Since these chemically peculiar stars, called "Li-rich giants," attracted interest of astrophysicists, a number of studies have been published so far (see, e.g., Charbonnel & Balachandran 2000;Lèbre et al 2009;Carlberg et al 2010;Kumar et al 2011;Monaco et al 2011;Martell & Shetrone 2013;Silva Aguirre et al 2014;Reddy & Lambert 2016;Casey et al 2016; and the references therein). Nonetheless, the reason why such significant amount of Li atoms are existent in their atmospheres (unlike other normal giants) has not been clarified yet, though various mechanisms have been proposed so far (cf.…”

Section: Introductionmentioning

confidence: 99%

On the observational characteristics of lithium-enhanced giant stars in comparison with normal red giants

Takeda

Tajitsu²

2017

Publications of the Astronomical Society of Japan

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While lithium is generally deficient in the atmosphere of evolved giant stars because of the efficient mixing-induced dilution, a small fraction of red giants show unusually strong Li lines indicative of conspicuous abundance excess. With an aim to shed light on the origin of these peculiar stars, we carried out a spectroscopic study on the observational characteristics of selected 20 bright giants already known to be Li-rich from past studies, in comparison with the reference sample of a large number of normal late G -early K giants. Our special attention was paid to clarifying any difference between the two samples from a comprehensive point of view (i.e., with respect to stellar parameters, rotation, activity, kinematic properties, 6 Li/ 7 Li ratio, and the abundances of Li, Be, C, O, Na, S, and Zn). Our sample stars are roughly divided into "bump/clump group" and "luminous group" according to the positions on the HR diagram. Regarding the former group (1.5 < ∼ log(L/L ⊙ ) < ∼ 2 and M ∼1.5-3 M ⊙ ), Li-enriched giants and normal giants appear practically similar in almost all respect except for Li, suggesting that surface Li enhancement in this group may be a transient episode which normal giants undergo at certain evolutionary stages in their lifetime. Meanwhile, those Li-rich giants belonging to the latter group (log(L/L ⊙ ) ∼ 3 and M ∼3-5 M ⊙ ) appear more anomalous in the sense that they tend to show higher rotation as well as higher activity, and that their elemental abundances (especially those derived from high-excitation lines) are apt to show apparent overabundances, though this might be due to a spurious effect reflecting the difficulty of abundance derivation in stars of higher rotation and activity. Our analysis confirmed considerable Be deficiency as well as absence of 6 Li as the general characteristics of Li-rich giants under study, which implies that engulfment of planets is rather unlikely for the origin of Li-enrichment.

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“…Thus the severe depletion of Li in the atmosphere of a giant star is the natural consequence of stellar evolution (Iben 1967a,b). Assuming 2005; Kumar et al 2011;Ruchti et al 2011;Kirby et al 2012;Martell & Shetrone 2013;Adamów et al 2014;Casey et al 2016;Li et al 2018;Smiljanic et al 2018;Deepak & Reddy 2019;Zhou et al 2019;Singh et al 2019a,b). Furthermore, a number of Li-rich giants with special features have been found (e.g., Kumar & Reddy 2009;Adamów et al 2012;Silva Aguirre et al 2014;Yan et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Lithium-rich Giants in LAMOST Survey. I. The Catalog

Gao

Shi

Yan

et al. 2019

ApJS

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Standard stellar evolution model predicts a severe depletion of lithium (Li) abundance during the first dredge up process (FDU). Yet a small fraction of giant stars are still found to preserve a considerable amount of Li in their atmospheres after the FDU. Those giants are usually identified as Li-rich by a widely used criterion, A(Li) > 1.5 dex. A large number of works dedicated to searching for investigating this minority of the giant family, and the amount of Li-rich giants, has been largely expanded on, especially in the era of big data. In this paper, we present a catalog of Li-rich giants found from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey with Li abundances derived from a template-matching method developed for LAMOST low-resolution spectra. The catalog contains 10, 535 Li-rich giants with Li abundances from ∼ 1.5 to ∼ 4.9 dex. We also confirm that the ratio of Li-rich phenomenon among giant stars is about 1%-or more specifically, 1.29%-from our statistically important sample. This is the largest Li-rich giant sample ever reported to date, which significantly exceeds amount of all the reported Li-rich giants combined. The catalog will help the community to better understand the Li-rich phenomenon in giant stars. an initial abundance of A(Li) 1 = 3.3 dex for a main sequence star of approximately solar metallicity and mass above ∼ 1.4 M ⊙ , diluted for ∼ 60 times due to FDU, its Li abundance will be below 1.5 dex when it finishes FDU.The predicted depletion has been confirmed by a large number observations of giants (Brown et al. 1989;Lind et al. 2009; Kirby et al. 2016, for example). However, Wallerstein & Sneden reported a K giant with A(Li) up to 3.2 dex in 1982. Since then, about 600 giants with A(Li) over 1.5 dex were reported with object-ID/positions and Li abundances (e.g., Brown et al. 1989; Reddy & Lambert 1 A(Li) = log[N Li /N H + 12, where N Li and N H is the number density of lithium and hydrogen, respectively.

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TheGaia-ESO Survey: revisiting the Li-rich giant problem

Cited by 83 publications

References 128 publications

Abundance analyses of Li-enriched and normal giants in the GALAH survey

Abundance analyses of Li-enriched and normal giants in the GALAH survey

On the observational characteristics of lithium-enhanced giant stars in comparison with normal red giants

Lithium-rich Giants in LAMOST Survey. I. The Catalog

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