Episodic Mass Loss and Rapid Lithium Enrichment and Depletion in K Giants

1998 ◽  
pp. 291-292
Author(s):  
R. De La Reza ◽  
N. A. Drake ◽  
L. Da Silva
Keyword(s):  
Mass Loss ◽  
Lithium Enrichment ◽  
K Giants

scholarly journals Li Enrichment, Mass Loss, and CN Abundances in High Rotating K Giants

2004 ◽  
Vol 215 ◽  
pp. 242-243
Author(s):  
N. A. Drake ◽  
R. de la Reza ◽  
L. da Silva ◽  
D. L. Lambert
Keyword(s):  
Mass Loss ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
Mixing Process ◽  
Stellar Activity ◽  
New Models ◽  
Low Mass ◽  
K Giants

High rotating low-mass K giants can be considered as interesting new “laboratories” for studies of the mixing process and mass loss. By means of high spectral resolution observations of some rapidly rotating K giants we found a series of connections between rotation, stellar activity, high Li abundance and mass loss. These giants show low 14N and high 13C enrichment. Nearly half of them are Li rich. This frequency is much higher than the ~ 2% corresponding to common, low rotating K giants. They are also the most suitable objects to test new models of rotation-induced mixing or planet engulfing scenarios.

scholarly journals Lithium in Giant Stars

2000 ◽  
Vol 198 ◽  
pp. 310-319 ◽  
Author(s):  
Ramiro de la Reza
Keyword(s):  
Mass Loss ◽  
Chemical Evolution ◽  
Light Elements ◽  
Evolutionary Mechanisms ◽  
Set Constraints ◽  
Giant Stars ◽  
Mass Losses ◽  
The Galaxy ◽  
Lithium Enrichment ◽  
State Of Art

Lithium continues to be a surprising element and more than ever the study of its creation, destruction and distribution is giving us tools to understand, not only the chemical evolution of this element, but also the nature of mass loss of evolved giants and nucleosynthesis of other elements in cases of very low-metal giants. It also helps to set constraints for cosmological models. The presence of very strong lithium lines in some giant stars of different spectral types and stages of evolution has been considered up to the end of the nineties as a puzzle. To solve this problem, non standard evolutionary mechanisms must be invoked. We review here all the mechanisms presented in the literature and which are divided into internal and external processes of lithium enrichment. We will also discuss the observational tests which are being performed in order to discard (or not) some of them. In any case, the more realistic values of the lithium abundances in giants are, as we will see, the main test of these proposed scenarios. Because of this importance we discuss here the state of art of the Non-LTE determinations of lithium abundances in strong lithium giants. Evolved giants, with lithium abundances larger than that of the interstellar medium and with their important mass losses can be considered the most realistic sources of lithium in the Galaxy. We believe that a complete physical picture of this problem will give a powerful tool to understand the chemical evolution of a large part of all light elements.

scholarly journals ORIGIN OF LITHIUM ENRICHMENT IN K GIANTS

2011 ◽  
Vol 730 (1) ◽  
pp. L12 ◽  
Author(s):  
Yerra Bharat Kumar ◽  
Bacham E. Reddy ◽  
David L. Lambert
Keyword(s):  
Lithium Enrichment ◽  
K Giants

Lithium enrichment in the Galaxy: A study using the GALAH and Gaia surveys

2019 ◽  
Vol 14 (S353) ◽  
pp. 16-18
Author(s):  
Deepak ◽  
Bacham E. Reddy
Keyword(s):  
Mass Loss ◽  
Large Sample ◽  
Giant Stars ◽  
The Galaxy ◽  
Low Mass ◽  
Promising Source ◽  
Lithium Enrichment

AbstractHere, we explore the enrichment of Lithium in the Galaxy using a large sample of stars common among large spectroscopic surveys such as the GALAH and astrometric survey by the Gaia satellite. For this study we used about 60,000 low mass (M⩽ 2M⊙) dwarfs from the GALAH survey. Further, we discuss Li enrichment among giant stars based on a sample of 52,000 low mass giants, of which 335 are Li-rich with A(Li) ⩾ 1.80 ± 0.14 dex, culled from the GALAH survey. These low mass giants appears to be one of the promising source of Li enrichment in the Galaxy as their atmospheric Li can be added to the ISM through mass loss.

scholarly journals Far-infrared study of K giants in the solar neighborhood: Connection between Li enrichment and mass-loss

2015 ◽  
Vol 577 ◽  
pp. A10 ◽  
Author(s):  
Yerra Bharat Kumar ◽  
B. E. Reddy ◽  
C. Muthumariappan ◽  
G. Zhao
Keyword(s):  
Mass Loss ◽  
Far Infrared ◽  
Solar Neighborhood ◽  
Infrared Study ◽  
K Giants

scholarly journals The s-Process in the Yellow Symbiotic AG Draconis

2000 ◽  
Vol 177 ◽  
pp. 103-104
Author(s):  
Katia Cunha ◽  
Verne V. Smith ◽  
Alain Jorissen
Keyword(s):  
Mass Loss ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Element Abundance ◽  
Neutron Density ◽  
Symbiotic Stars ◽  
Solar Metallicity ◽  
Low Metallicity ◽  
K Giants

An abundance analysis of the yellow symbiotic system AG Draconis reveals it to be a metal-poor K giant ([Fe/H] = −1.3) which is enriched in the heavy s-process elements. This star thus provides a link between the symbiotic stars and the binary barium and CH stars which are also s-process enriched. These binary systems, which exhibit overabundances of the heavy elements, owe their abundance peculiarities to mass transfer from thermally-pulsing asymptotic giant branch stars, which have since evolved to become white-dwarf companions of the cool stars we now view as the chemically peculiar primaries. A comparison of the heavy-element abundance distribution in AG Dra with theoretical nucleosynthesis calculations shows that the s-process is defined by a relatively large neutron exposure (τ = 1.3 mb−1), while an analysis of the rubidium abundance suggests that the s-process occurred at a neutron density of about 2 × 108 cm−3. The derived spectroscopic orbit of AG Dra is similar to the orbits of barium and CH stars. Because the luminosity function of low-metallicity K giants is skewed towards higher luminosities by about 2 magnitudes relative to solar-metallicity giants, it is argued that the lower metallicity K giants have larger mass-loss rates. It is this larger mass-loss rate that drives the symbiotic phenomena in AG Dra and we suggest that the other yellow symbiotic stars are probably low-metallicity objects as well.

Lithium Enrichment–Mass-Loss Connection in K Giant Stars

1996 ◽  
Vol 456 (2) ◽  
Author(s):  
R. de la Reza, ◽  
N. A. Drake, ◽  
L. da Silva
Keyword(s):  
Mass Loss ◽  
Giant Stars ◽  
Lithium Enrichment

Water accumulation as a function of temperature on specimens in an electron microscope cold stage

1986 ◽  
Vol 44 ◽  
pp. 114-115 ◽  
Author(s):  
M.K. Lamvik ◽  
D.A. Kopf ◽  
S.D. Davilla ◽  
J.D. Robertson
Keyword(s):  
Electron Microscope ◽  
Mass Loss ◽  
Liquid Helium ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Cold Stage ◽  
Water Accumulation ◽  
Better Than

Last year we reported1 that there is a striking reduction in the rate of mass loss when a specimen is observed at liquid helium temperature. It is important to determine whether liquid helium temperature is significantly better than liquid nitrogen temperature. This requires a good understanding of mass loss effects in cold stages around 100K.

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