The Effect of Photospheric Granulation on the Determination of the Lithium Abundance in Solar‐type Stars

1998 ◽  
Vol 498 (1) ◽  
pp. 427-440 ◽  
Author(s):  
H. Uitenbroek
Keyword(s):  
Lithium Abundance ◽  
Solar Type

scholarly journals Lithium Observations in the Sun

1968 ◽  
Vol 1 ◽  
pp. 243-246
Author(s):  
Edith A. Müller
Keyword(s):  
Unknown Origin ◽  
Absorption Feature ◽  
The Sun ◽  
Degree Of Ionization ◽  
Lithium Abundance ◽  
Resonance Doublet ◽  
Lower Temperature ◽  
Central Depth ◽  
The Continuum

The determination of the lithium abundance in the solar atmosphere is essentially based on the LiI resonance doublet at λ 6707·761 and 6707·912 Å. These two lines form a very faint absorption feature, the central depth of the stronger component being of the order of 1% of the continuum. The violet component, which is also the stronger of the two, occurs near the red wing of a faint solar line of unknown origin, and the lines appear to be blended with other faint lines including possibly the doublet of the Li6 isotope (the isotopic shift being 0·160 Å). No other line of LiI has been detected in the Fraunhofer spectum of the undisturbed solar disk. This is nothing surprising, because practically all lithium is expected to be ionized in the photosphere on account of its low ionization potential (Xion = 5·37 e.v.). In sunspot spectra the lower temperature reduces the degree of ionization of lithium and causes a strengthening of the LiI lines. In fact, the LiI resonance lines which appear as a very faint absorption feature on disk spectra are about 50 times stronger in spot spectra. Furthermore, the very weak feature at λ 6103·6 Å was identified by Dubov (1964) and by Schmahl and Schröter (1965) as due to the 2s 2S–3d 2D transition of LiI. Both the resonance doublet and the faint feature at 6103·6 Å have been used by the above-mentioned authors to derive the lithium abundance in spots.

scholarly journals Lithium Abundance of the Solar-Type Superflare Stars

2017 ◽  
Author(s):  
Satoshi Honda ◽  
Yuta Notsu ◽  
Hiroyuki Maehara ◽  
Shota Notsu ◽  
Takuya Shibayama ◽  
...  
Keyword(s):  
Lithium Abundance ◽  
Solar Type

scholarly journals Lithium Depletion in a [Fe/H]= —3.4 star?

2000 ◽  
Vol 198 ◽  
pp. 356-357 ◽  
Author(s):  
M. Spite ◽  
F. Spite ◽  
R. Cayrel ◽  
V. Hill ◽  
E. Depagne ◽  
...  
Keyword(s):  
High Quality ◽  
Lithium Abundance ◽  
Lithium Depletion ◽  
Metal Poor Star

We present a determination of the lithium abundance from high quality spectra in an extremely metal poor star where the lithium line had not been detected.

scholarly journals Lithium Abundance and Activity for 57 Rs Cvn Systems

1993 ◽  
Vol 137 ◽  
pp. 657-657
Author(s):  
Liu Xuefu ◽  
Zhao Gang ◽  
Tan Huisong ◽  
Lu Fangjun
Keyword(s):  
Model Atmosphere ◽  
Spectral Lines ◽  
High Signal ◽  
Activity Levels ◽  
Lithium Abundance ◽  
Cool Component ◽  
Rs Cvn Stars ◽  
Metal Abundance ◽  
Line Analysis

AbstractHigh-resolution (0.145A/diode, high signal-to-noise (> 100) Reticon spectra of 57 RS CVn systems, which were observed with the coudé spectrographs of the McDonald 2.1m telescope and Yunnan lm telescope, were used to analyse a correlation between Li abundance and chromospere activity. Li abundances of 57 RS CVn stars, which include 76 detected components have been determined through the determination of equivalent widths of Li doublet (6707.761A + 6707.912A) and Kuruz’s model atmosphere. The model metal abundance and line analysis of 10 RS CVn stars were determined from the present spectral lines data. The main results are the following: 1, Lithium abunances of 76 RS CVn components for 57 RS CVn systems are obviously reduced with the the effective temperatures gradually decreasing. 2, Li abundance has staistically decreasing trend in RS CVn stars with the rotational velocities vsini increasing. 2, The position of 168 RS CVn stars in the (U-B, B-V) Figure show that they can be devided into two groups. The most of them seem to be not poor-metal stars. Li abundances of these stars seem to have no obious correlations with their stellar chromosphery activity levels, but 7 RS CVn systems, in which cool component is more active show that the more active component has a lower Li abundance.

New results of the spectral observations of CP stars

2009 ◽  
Vol 5 (S268) ◽  
pp. 351-354
Author(s):  
N. S. Polosukhina ◽  
A. V. Shavrina ◽  
N. A. Drake ◽  
D. O. Kudryavtsev ◽  
M. A. Smirnova
Keyword(s):  
Magnetic Fields ◽  
Chemical Elements ◽  
Individual Characteristics ◽  
Physical Origin ◽  
Surface Distribution ◽  
Lithium Abundance ◽  
Phase Rotation ◽  
Long Time ◽  
Resonance Doublet

AbstractThe lithium problem in Ap-CP stars has been, for a long time, a subject of debate. Individual characteristics of CP stars, such as high abundance of the rare-earth elements presence of magnetic fields, complicate structure of the surface distribution of chemical elements, rapid oscillations of some CP-stars, make the detection of the lithium lines and the determination of the lithium abundance, a difficult task. During the International Meeting in Slovakia in 1996, the lithium problem in Ap-CP stars was discussed. The results of the Li study carried out in CrAO Polosukhina (1973–1976), the works of Hack & Faraggiana (1963), Wallerstein & Hack (1964), Faraggiana et al. (1992–1996) formed the basis of the International project ‘Lithium in the cool CP-stars with magnetic fields’. The main goal of the project was, using systematical observations of Ap-CP stars with phase rotation in the spectral regions of the resonance doublet Li I 6708 Å and subordinate 6104 Å lithium lines with different telescopes, to create a database, which will permit to explain the physical origin of anomalous Li abundance in the atmospheres of these stars.

scholarly journals Detailed abundances in a sample of very metal-poor stars

2020 ◽  
Vol 642 ◽  
pp. A25
Author(s):  
P. François ◽  
S. Wanajo ◽  
E. Caffau ◽  
N. Prantzos ◽  
W. Aoki ◽  
...  
Keyword(s):  
Chemical Composition ◽  
First Generation ◽  
Sloan Digital Sky Survey ◽  
Lithium Abundance ◽  
Sky Survey ◽  
Upper Limits ◽  
The Galaxy ◽  
Chemical History ◽  
Metal Poor Star

Context. Unevolved metal-poor stars bore witness to the early evolution of the Galaxy, and the determination of their detailed chemical composition is an important tool to understand its chemical history. The study of their chemical composition can also be used to constrain the nucleosynthesis of the first generation of supernovae that enriched the interstellar medium. Aims. We aim to observe a sample of extremely metal-poor star (EMP stars) candidates selected from the Sloan Digital Sky Survey data release 12 (SDSS DR12) and determine their chemical composition. Methods. We obtained high-resolution spectra of a sample of five stars using HDS on Subaru telescope and used standard 1D models to compute the abundances. The stars we analysed have a metallicity [Fe/H] of between −3.50 and −4.25 dex. Results. We confirm that the five metal-poor candidates selected from low-resolution spectra are very metal poor. We present the discovery of a new ultra metal-poor star (UMP star) with a metallicity of [Fe/H] = −4.25 dex (SDSS J1050032.34−241009.7). We measured in this star an upper limit of lithium (log(Li/H) ≤ 2.0. We found that the four most metal-poor stars of our sample have a lower lithium abundance than the Spite plateau lithium value. We obtain upper limits for carbon in the sample of stars. None of them belong to the high carbon band. We measured abundances of Mg and Ca in most of the stars and found three new α-poor stars.

scholarly journals Transport Phenomena and Light Element Abundances in the Sun and Solar Type Stars

2000 ◽  
Vol 198 ◽  
pp. 470-475
Author(s):  
Sylvie Vauclair
Keyword(s):  
Diffusion Processes ◽  
Light Element ◽  
The Sun ◽  
Mixing Processes ◽  
Lithium Abundance ◽  
Solar Convection Zone ◽  
Element Abundances ◽  
Solar Convection ◽  
Halo Stars ◽  
Solar Type

The observations of light elements in the Sun and Solar type stars give special clues for understanding the hydrodynamical processes at work in stellar interiors. In the Sun 7Li is depleted by 140 while 3He has not increased by more than ≅ 10% in 3 Gyrs. Meanwhile the inversion of helioseismic modes lead to a precision on the sound velocity of about 1%. The mixing processes below the solar convection zone are constrained by these observations. Lithium is depleted in most Pop I solar type stars. In halo stars however, the lithium abundance seems constant in the “spite plateau” with no observed dispersion, which is difficult to reconcile with the theory of diffusion processes. In the present paper, the various relevant observations will be discussed. It will be shown that the μ-gradients induced by element settling may help solving the ‘lithium paradox’.

scholarly journals Laboratory spectroscopic study of the 15N isotopomers of cyanamide, H2NCN, and a search for them toward IRAS 16293−2422 B

2019 ◽  
Vol 623 ◽  
pp. A93 ◽  
Author(s):  
Audrey Coutens ◽  
Olena Zakharenko ◽  
Frank Lewen ◽  
Jes K. Jørgensen ◽  
Stephan Schlemmer ◽  
...  
Keyword(s):  
Laboratory Data ◽  
Natural Isotopic Composition ◽  
Interstellar Molecules ◽  
Spectroscopic Parameters ◽  
Rotational Spectra ◽  
Isotopic Species ◽  
Upper Limits ◽  
Solar Type ◽  
Line Survey

Context. Cyanamide is one of the few interstellar molecules containing two chemically different N atoms. It was detected recently toward the solar-type protostar IRAS 16293−2422 B together with H2N13CN and HDNCN in the course of the Atacama Large Millimeter/submillimeter Array (ALMA) Protostellar Interferometric Line Survey (PILS). The detection of the 15N isotopomers or the determination of upper limits to their column densities was hampered by the lack of accurate laboratory data at the frequencies of the survey. Aims. We wanted to determine spectroscopic parameters of the 15N isotopomers of cyanamide that are accurate enough for predictions well into the submillimeter region and to search for them in the PILS data. Methods. We investigated the laboratory rotational spectra of H215NCN and H2NC15N in the selected region between 192 and 507 GHz employing a cyanamide sample in natural isotopic composition. Additionally, we recorded transitions of H2N13CN. Results. We obtained new or improved spectroscopic parameters for the three isotopic species. Neither of the 15N isotopomers of cyanamide were detected unambiguously in the PILS data. Two relatively clean lines can be tentatively assigned to H215NCN. If confirmed, their column densities would imply a low 14N/15N ratio for cyanamide toward this source. Conclusions. The resulting line lists should be accurate enough for observations up to about 1 THz. More sensitive observations, potentially at different frequencies, may eventually lead to the astronomical detection of these isotopic species.

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