Lithium lines in spectra of C-giants
The resonance λ 670.8 nm and subordinate λλ 812.6, 610.4, 497.2, and 460.3 nm lithium lines are investigated as the lithium abundance indicators in spectra of cool C-giants.
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| Date: | 2005 |
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Головна астрономічна обсерваторія НАН України
2005
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| Cite this: | Lithium lines in spectra of C-giants / L.A. Yakovina, Ya.V. Pavlenko // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 259-261. — Бібліогр.: 7 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859703275874418688 |
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| author | Yakovina, L.A. Pavlenko, Ya.V. |
| author_facet | Yakovina, L.A. Pavlenko, Ya.V. |
| citation_txt | Lithium lines in spectra of C-giants / L.A. Yakovina, Ya.V. Pavlenko // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 259-261. — Бібліогр.: 7 назв. — англ. |
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| container_title | Кинематика и физика небесных тел |
| description | The resonance λ 670.8 nm and subordinate λλ 812.6, 610.4, 497.2, and 460.3 nm lithium lines are investigated as the lithium abundance indicators in spectra of cool C-giants.
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| first_indexed | 2025-12-01T01:47:39Z |
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LITHIUM LINES IN SPECTRA OF C-GIANTS
L. A. Yakovina, Ya. V. Pavlenko
Main Astronomical Observatory, NAS of Ukraine
27 Akademika Zabolotnoho Str., 03680 Kyiv, Ukraine
e-mail: yakovina@mao.kiev.ua
The resonance λ 670.8 nm and subordinate λλ 812.6, 610.4, 497.2, and 460.3 nm lithium lines are
investigated as the lithium abundance indicators in spectra of cool C-giants.
INTRODUCTION
The lithium abundance in stellar atmospheres provides information on various details of the stellar evolution
and physical processes in stars. Among lithium-rich stars AGB, Li-rich (logN(Li) ≥ 1 in scale logN(H)= 12.0)
and super Li-rich giants (SLR, logN(Li) ≥ 4) are of great cosmological interest, because they belong to the main
suppliers of lithium into the interstellar medium.
The resonance Li I line λ 670.8 nm is usually strong and sometimes very strong in spectra of cool C-stars.
Besides, there are some subordinate Li I lines in optical and near IR regions that can also be strong in spectra of
lithium-rich C-giants. Four lines formed by transitions from a level 2p are in the range λλ 450–820 nm, namely,
λλ 812.6, 610.4, 497.2, and 460.3 nm. From the computations [5, 7] follows that only the Li I lines λλ 812.6,
670.8, 610.4, and 497.2 nm can be used as the lithium abundance indicators in spectra of C-giants. The line
λ 460.3 nm is severely blended by the Fe I line at the same wavelength [6].
Different lithium lines are quite strong and sensitive to the lithium abundance for different values logN(Li).
So, the Li I lines λλ 812.6 and 610.4 nm are saturated in spectra of SLR C-stars and, therefore, they are rather
non sensitive to the lithium abundance. But the Li I line λ 497.2 nm is quite strong and sensitive to the lithium
abundance for logN(Li)= 3–5 [5, 7].
We use for the calculations a model atmosphere and parameters of the spectra of the J-type star WZ Cas
(C9.2J).
PROCEDURE
The profiles of the lithium lines were computed using the LTE approach realized in the program WITA6 [4].
Continuum opacities for a case of carbon-rich atmospheres were used. Then, we implemented an additional
continuum absorption to account of unidentified yet sources by increasing of a continuum opacity by factor κ.
Parameters of the used for WZ Cas model atmosphere (see [2]) are as follows: Teff/log g/[μ]= 3000/0/0,
C/O=1.007. We adopted oxygen and nitrogen abundances from the model atmosphere and used carbon
abundances obtained in our previous work [7] from the fits to an observed spectrum. The microturbulence
velocity Vt = 2.5 km/s and isotopic ratio 12C/13C =5 were used (see [1]). Parameters of Li lines were taken from
VALD [3]. We calculated the profiles of the Li I lines λλ 812.6, 670.8, 610.4, and 497.2 nm for logN(Li)=−2÷+5
and analyzed this lines as possible lithium abundance indicators. We used in our calculations κ, logN(C), and
a half width of the smoothing gaussian δ, which were chosen for WZ Cas in [7].
RESULTS
The calculated profiles of the four Li I lines for various lithium abundances are showed in Fig. 1. It is worth
noting:
• The core of the resonance Li I line λ 670.8 nm is very sensitive to the lithium abundance for logN(Li) =
−2 ÷ 0. For logN(Li) > 0 the core of resonance Li I line becomes saturated and shows a low sensitivity
to the lithium abundance. But for logN(Li) ≥ 3 the wings of the resonance line become strong. Their
intensities are highly sensitive to the lithium abundances and we can derive logN(Li) from this wings.
• The subordinate Li I line λ 812.6 nm is very sensitive to the lithium abundance for logN(Li)= 1.5–3.5.
c© L. A. Yakovina, Ya. V. Pavlenko, 2004
259
Figure 1. Profiles of Li I lines calculated with a model atmosphere 3000/0/0, C/O =1.007 for various log N(Li)
260
• The subordinate Li I line λ 610.4 nm is very sensitive to the lithium abundance for logN(Li)= 1.0–3.0.
• The subordinate Li I line λ 497.2 nm is very sensitive to the lithium abundance for logN(Li)= 3.0–5.0.
As result, we see that in spectra of cool C-giants for logN(Li)< 1 only the resonance lithium line at
λ 670.8 nm can be a lithium abundance indicator. For 0 < logN(Li)< 3 this line is not a very good indi-
cator due to a weak sensitivity on logN(Li). For logN(Li) ≈ 1–3.5, the subordinate Li I lines at λλ 610.4 nm
and 812.6 nm must be the best lithium abundance indicators. Then, in SLR C-stars the resonance Li I line and
the line Li I λ 497.2 nm should be the best lithium abundance indicators.
The real situation with lithium abundance indicators is more complicate due to the blending of all lithium
lines by atomic and molecular lines. The blending reduces the sensitivity of the lithium lines on logN(Li).
In optical spectra of C-giants the bulk of molecular lines belong to molecules C2 and CN. The strong telluric
absorption exists in region of the Li I line at λ 812.6 nm. We should use the most complete and exact line lists
to take into account the blending near lithium lines. We note that the line lists used in [1] and [7] are not quite
perfect. The situation is more simple for SLR stars due to very strong lithium lines, but for normal lithium
abundances the situation with the line lists is crucial.
Now we can present some conclusions on lithium abundances in SLR C-giants which we obtained by studying
the four lines [1, 7]:
• Both the LTE and NLTE logN(Li) values derived for the λ 497.2 nm line are equal to or a bit lower than
estimations for the λ 670.8 nm line (Δ log N(Li) ≤ 0.4).
• Lithium abundances for the λ 610.4 nm line are essentially (by ≈ 1 dex) lower a those for the resonance
line.
• The estimations for the line λ 812.6 nm are equal to or higher then those for the λ 670.8 nm line. NLTE
corrections improve the agreement in logN(Li) for these lines.
DISCUSSION
Our results show that the subordinate lithium lines can be good lithium abundance indicators for Li-rich
(logN(Li)> 1) stars. This conclusion was tested for SLR C-giants [1, 7]. The last research confirms that
the resonance λ 670.8 nm and subordinate λ 497.2 nm Li I lines are the best lithium abundance indicators in
spectra of SLR C-giants.
[1] Abia C., Pavlenko Y., de Laverny P. The formation of lithium lines in the atmospheres of super Li-rich AGB
stars // Astron. and Astrophys.–1999.–351, N 2.–P. 273–282.
[2] Eriksson K., Gustafsson B., et al. Effects of HCN molecules in carbon star atmospheres // Astron. and Astrophys.–
1984.–132, N 1.–P. 37–44.
[3] Kupka F., Piskunov N., et al. VALD-2: Progress of the Vienna Atomic Line Data Base // Astron. and Astrophys.
Suppl. Ser.–1999.–138, N 1.–P. 119–133.
[4] Pavlenko Ya. V. Lithium Lines in the Spectra of M Dwarfs: UX Tau C // Astron. Rep.–2000.–77, N 4.–P. 254–263.
[5] Yakovina L. A., Pavlenko Ya. V. On the lithium abundance determination in the atmospheres of super lithium-rich
carbon stars using the resonance and subordinate Li I lines. I // Kinematics and Physics of Celestial Bodies.–2001.–
17, N 5.–P. 446–458.
[6] Yakovina L. A., Pavlenko Ya. V. Li I line λ 460.3 nm in spectra of super lithium-rich carbon stars // Odessa
Astron. Publ.–2001.–14.–P. 253–254.
[7] Yakovina L. A., Pavlenko Ya. V. On the lithium abundance determination in the atmospheres of super lithium-rich
carbon stars using the resonance and subordinate Li I lines. II // Kinematics and Physics of Celestial Bodies.–2002.–
18, N 2.–P. 99–113.
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| id | nasplib_isofts_kiev_ua-123456789-79653 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0233-7665 |
| language | English |
| last_indexed | 2025-12-01T01:47:39Z |
| publishDate | 2005 |
| publisher | Головна астрономічна обсерваторія НАН України |
| record_format | dspace |
| spelling | Yakovina, L.A. Pavlenko, Ya.V. 2015-04-03T17:36:41Z 2015-04-03T17:36:41Z 2005 Lithium lines in spectra of C-giants / L.A. Yakovina, Ya.V. Pavlenko // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 259-261. — Бібліогр.: 7 назв. — англ. 0233-7665 https://nasplib.isofts.kiev.ua/handle/123456789/79653 The resonance λ 670.8 nm and subordinate λλ 812.6, 610.4, 497.2, and 460.3 nm lithium lines are investigated as the lithium abundance indicators in spectra of cool C-giants. en Головна астрономічна обсерваторія НАН України Кинематика и физика небесных тел MS3: Physics of Stars and Galaxies Lithium lines in spectra of C-giants Article published earlier |
| spellingShingle | Lithium lines in spectra of C-giants Yakovina, L.A. Pavlenko, Ya.V. MS3: Physics of Stars and Galaxies |
| title | Lithium lines in spectra of C-giants |
| title_full | Lithium lines in spectra of C-giants |
| title_fullStr | Lithium lines in spectra of C-giants |
| title_full_unstemmed | Lithium lines in spectra of C-giants |
| title_short | Lithium lines in spectra of C-giants |
| title_sort | lithium lines in spectra of c-giants |
| topic | MS3: Physics of Stars and Galaxies |
| topic_facet | MS3: Physics of Stars and Galaxies |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79653 |
| work_keys_str_mv | AT yakovinala lithiumlinesinspectraofcgiants AT pavlenkoyav lithiumlinesinspectraofcgiants |