Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473
The lithium lines at 6708 Å for two sharp-lined roAp stars γ Equ and HD 166473 and at 6103 Å for γ Equ were analyzed in high resolution spectra. Three spectral synthesis codes – STARSP, ZEEMAN2, and SYNTHM – were used. New lines of the rare-earth elements from the DREAM database and lines calculated...
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Головна астрономічна обсерваторія НАН України
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| Цитувати: | Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 / A. Shavrina, N. Polosukhina, S. Khan, Ya. Pavlenko, V. Khalack, G.A. Wade, P. Quinet, N. Mikhailitska, A. Yushchenko, V. Gopka, D. Kudryavtsev // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 295-298. — Бібліогр.: 16 назв. — англ. |
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irk-123456789-796622015-04-04T03:02:11Z Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 Shavrina, A. Polosukhina, N. Khan, S. Pavlenko, Ya. Khalack, V. Wade, G.A. Quine, t P. Mikhailitska, N. Yushchenko, A. Gopka, V. Kudryavtsev, D. MS3: Physics of Stars and Galaxies The lithium lines at 6708 Å for two sharp-lined roAp stars γ Equ and HD 166473 and at 6103 Å for γ Equ were analyzed in high resolution spectra. Three spectral synthesis codes – STARSP, ZEEMAN2, and SYNTHM – were used. New lines of the rare-earth elements from the DREAM database and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars and high estimates of ⁶Li/⁷Li ratio (0.2 ÷ 0.5) can be explained by the Galactic Cosmic Ray (GCR) production due to spallation reactions and the preservation of original ⁶Li and ⁷Li by strong magnetic fields. 2005 Article Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 / A. Shavrina, N. Polosukhina, S. Khan, Ya. Pavlenko, V. Khalack, G.A. Wade, P. Quinet, N. Mikhailitska, A. Yushchenko, V. Gopka, D. Kudryavtsev // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 295-298. — Бібліогр.: 16 назв. — англ. 0233-7665 http://dspace.nbuv.gov.ua/handle/123456789/79662 en Кинематика и физика небесных тел Головна астрономічна обсерваторія НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
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English |
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MS3: Physics of Stars and Galaxies MS3: Physics of Stars and Galaxies |
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MS3: Physics of Stars and Galaxies MS3: Physics of Stars and Galaxies Shavrina, A. Polosukhina, N. Khan, S. Pavlenko, Ya. Khalack, V. Wade, G.A. Quine, t P. Mikhailitska, N. Yushchenko, A. Gopka, V. Kudryavtsev, D. Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 Кинематика и физика небесных тел |
| description |
The lithium lines at 6708 Å for two sharp-lined roAp stars γ Equ and HD 166473 and at 6103 Å for γ Equ were analyzed in high resolution spectra. Three spectral synthesis codes – STARSP, ZEEMAN2, and SYNTHM – were used. New lines of the rare-earth elements from the DREAM database and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars and high estimates of ⁶Li/⁷Li ratio (0.2 ÷ 0.5) can be explained by the Galactic Cosmic Ray (GCR) production due to spallation reactions and the preservation of original ⁶Li and ⁷Li by strong magnetic fields. |
| format |
Article |
| author |
Shavrina, A. Polosukhina, N. Khan, S. Pavlenko, Ya. Khalack, V. Wade, G.A. Quine, t P. Mikhailitska, N. Yushchenko, A. Gopka, V. Kudryavtsev, D. |
| author_facet |
Shavrina, A. Polosukhina, N. Khan, S. Pavlenko, Ya. Khalack, V. Wade, G.A. Quine, t P. Mikhailitska, N. Yushchenko, A. Gopka, V. Kudryavtsev, D. |
| author_sort |
Shavrina, A. |
| title |
Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 |
| title_short |
Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 |
| title_full |
Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 |
| title_fullStr |
Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 |
| title_full_unstemmed |
Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 |
| title_sort |
lithium and its isotopic ratio ⁶li/⁷li in the atmospheres of sharp-lined roap stars γ equulei and hd 166473 |
| publisher |
Головна астрономічна обсерваторія НАН України |
| publishDate |
2005 |
| topic_facet |
MS3: Physics of Stars and Galaxies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79662 |
| citation_txt |
Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473 / A. Shavrina, N. Polosukhina, S. Khan, Ya. Pavlenko, V. Khalack, G.A. Wade, P. Quinet, N. Mikhailitska, A. Yushchenko, V. Gopka, D. Kudryavtsev // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 295-298. — Бібліогр.: 16 назв. — англ. |
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Кинематика и физика небесных тел |
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LITHIUM AND ITS ISOTOPIC RATIO 6Li/7Li
IN THE ATMOSPHERES OF SHARP-LINED roAp STARS
γ EQUULEI and HD 166473
A. Shavrina1, N. Polosukhina2, S. Khan3, Ya. Pavlenko1, V. Khalack1, G. A. Wade4,
P. Quinet5, N. Mikhailitska1, A. Yushchenko6,7, V. Gopka6, D. Kudryavtsev8
1Main Astronomical Observatory, NAS of Ukraine
27 Akademika Zabolotnoho Str., 03680 Kyiv, Ukraine
e-mail: shavrina@mao.kiev.ua
2Scientific-Research Institute “Crimean Astrophysical Observatory”, Ukraine
e-mail: polo@crao.crimea.ua
3Tavrian National University, Simpheropol, Ukraine
e-mail: serg@starsp.org
4Physics Department, Royal Military College of Canada
e-mail: gregg.wade@rmc.ca
5Astrophysique et Spectroscopie, Universite de Mons-Hainaut, Belgium
e-mail: Pascal.Quinet@umh.ac.be
6Astronomical Observatory, Odesa National University, Ukraine
e-mail: yua@odessa.net, gopka@arktur.tenet.odessa.ua
7Astrophysical Research Center for the Structure and Evolution of the Cosmos
Sejong University, 143-747 Seoul, (South) Korea
8Special Astrophysical Observatory, Russian Academy of Sciences
Nizhny Arkhyz, Zelenchuk, 369167 Karachaevo-Cherkesiya, Russia
The lithium lines at 6708 Å for two sharp-lined roAp stars γ Equ and HD 166473 and at 6103 Å
for γ Equ were analyzed in high resolution spectra. Three spectral synthesis codes – STARSP,
ZEEMAN2, and SYNTHM – were used. New lines of the rare-earth elements from the DREAM
database and lines calculated on the basis of the NIST energy levels were included. Magnetic split-
ting and other line broadening processes were taken into account. Enhanced abundances of lithium
in the atmospheres of the stars and high estimates of 6Li/7Li ratio (0.2 ÷ 0.5) can be explained
by the Galactic Cosmic Ray (GCR) production due to spallation reactions and the preservation of
original 6Li and 7Li by strong magnetic fields.
INTRODUCTION
This research was carried out in the framework of the project “Lithium in CP stars” [8]. HD 201601 (γ Equ)
and HD 166473, both roAp stars, are characterized by sharp lines in their spectra, by the strong overabundance
of the rare-earth elements, and by strong magnetic fields (about 4.1 kG and 8.6 kG, respectively). The sharp
lines in the spectra of both stars result from their slow rotation: their periods are approximately 4 years for
HD 166473 and 77 years for γ Equ.
OBSERVED SPECTRA
The spectra of HD 166473 were obtained by P. North on March 8–14, 1996 with the 1.4-m Coude Auxiliary
Telescope (CAT) and Coude Echelle Spectrometer (CES) at La Silla. The detector was the ESO CCD N 34
with 2048 pixels along the dispersion direction (pixel size are 15 μm× 15 μm), which provides the resolving
power R = 100 000 and the wavelength range of 58.2 Å for the central wavelengths 6705, 6645, and 6150 Å.
In Table 1, we give the epoch, exposure time, and wavelength coverage of used spectra.
c© A. Shavrina, N. Polosukhina, S. Khan, Ya. Pavlenko, V. Khalack, G. A. Wade, P. Quinet, N. Mikhailitska, A. Yushchenko,
V. Gopka, D. Kudryavtsev, 2004
295
Table 1. The list of observations for HD 166473
N Date, d m yr T , UT hr min Exp., min HJD, 2450000+ Range
10 08.3.1996 8 23 80 150.876 6675–6735 Å
20 09.3.1996 8 48 50 151.883 6675–6735 Å
31 10.3.1996 8 45 60 152.884 6675–6735 Å
45 11.3.1996 8 48 60 153.886 6675–6735 Å
54 12.3.1996 8 38 60 154.880 6675–6735 Å
73 13.3.1996 8 52 50 155.886 6120–6180 Å
87 14.3.1996 8 36 60 156.878 6615–6675 Å
0.82
0.84
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
1.02
6706 6706.5 6707 6707.5 6708 6708.5
re
si
du
al
in
te
ns
ity
, r
wavelength, A
Ce II
I
Pr III
I
Li I
I
Li I
I
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
6147 6147.5 6148 6148.5 6149 6149.5
re
si
du
al
in
te
ns
ity
, r
wavelength, A
Cr II
I
Pr II
I
Fe II
I
Fe II
I
a) HD 166473, Li I 6708 Å b) HD 166473, Li I 6708 Å, Fe II 6149 Å
Figure 1. For HD 166473 (a) Li I 6708 Å, black: observed spectrum; red line: a calculated spectrum by taking into
account lines of only the main isotope 7Li, log N(Li)/N(H) = −8.2; green line: spectrum with the ratio 6Li/7Li = 0.4,
log N(Li)/N(H) = −8.3. The positions of those lines, which are the main contributors to the absorption, are marked at
the top of the figure. Note that the Pr III line model profile fits to the observed one for magnetic field parameters Br,
Bm, Bl = 3000, 5500, 0 G, respectively, while for the Li I line profile these parameters are 4000, 9000, 0 G, respectively.
(b) Fe II 6147 Å and 6149 Å lines, Br = 4.8 kG, Bm = 4.9 kG, Bl = 0 kG.
0.75
0.8
0.85
0.9
0.95
1
6706 6706.5 6707 6707.5 6708 6708.5
re
si
du
al
in
te
ns
ity
, r
wavelength, A
Ce II
I
Pr III
I
Li I
I
Li I
I
0.7
0.75
0.8
0.85
0.9
0.95
1
6102 6102.5 6103 6103.5 6104 6104.5
re
si
du
al
in
te
ns
ity
, r
wavelength, A
Fe I
I
Ca I
I
Fe I
I
Fe II
I
Li I
I
a) γ Equ, Li I 6708 Å b) γ Equ, Li I 6103 Å
Figure 2. For γ Equ (a) Li I 6708 Å, blue line: log N(Li) = −7.95, 6Li/7Li = 0.5; red line: log N(Li) = −7.80, only 7Li.
(b) Li I 6103 Å, 6103 Å, log N(Li)/N(H) = −8.0 and log N(Li)/N(H) = −8.3.
The observations of γ Equ were obtained on March 9–10, 2004 by D. Kudryavtsev with the 6-m BTA
telescope and Nasmyth Echelle Spectrometer (NES, Panchuk et al. [9]) of the Russian Special Astrophysical
Observatory. They consist of the continuous sequences of 25 and 16 spectra for March 9 and 10, respectively,
with exposure times of about 3 min that allows one to analyze the pulsational variability of spectral lines.
The spectra with signal-to-noise ratio of above 80 (15 and 4 spectra for March 9 and 10, respectively) did not
show any significant variability of the 6708 Å lithium line profiles and were selected for the analysis. In Fig. 2,
we show an averaged spectrum for March 9, which almost coincides with the similar one for March 10.
296
Table 2. Results of the determination of the Li abundances, 6Li/7Li ratio, magnetic field parameters as well as the v sin i
determination
HD 166473 HD 201601
Teff/log g/[min] 7750/4.0/0 7750/4.0/0
N(Fe I) 6103 Å – 7.80
N(Fe II) 6149 Å 7.60 7.50
N(Li) 6708 Å 3.7 3.8
N(Li) 6103 Å – 4.0
6Li/7Li, 6708 Å 0.4: 0.5:
Br/Bm/Bl/ (kG)
Fe II 6149 Å 4.8/4.9/0 3.5/2.6/0.8
Pr III 6706.7 Å 3.0/5.5/0 2.7/3.5/0
Ca I 6102.7 Å – 0/4.0/0
v sin i (km s−1) (Fe II) 3.0 0.5
v sin i (km s−1) (Pr III) 5.0 2.5
SYNTHETIC SPECTRA
These stars, HD 166473 and γ Equ, with the strong 6708 Å lithium doublets are not well studied. We analyzed
their spectra in detail in a narrow range near 6708 Å by the method of synthetic spectra, taking into account
the Zeeman magnetic splitting and blending by REE lines. The additional broadening, likely pulsational,
was described by the parameter v sin i. Spectral calculations for both stars were carried out using the model
atmospheres of [7] with parameters from [3, 10, 11]. For synthetic spectra calculations, we applied the magnetic
spectrum synthesis code SYNTHM [4], which is similar to the Piskunov code SYNTHMAG and was tested in
accordance with [15]. For initial calculations, we also used the code STARSP of [14] and in some cases the code
ZEEMAN2 [15]. We used the VALD [6] and DREAM1 databases for atomic spectral lines. These data do not
in fact allow us to fit synthetic spectra to the observed ones for all stars investigated. Therefore, we calculated
additional REE ii-iii lines using the NIST energy levels and estimated their “astrophysical” gf -values from
the spectra of HD 101065 using the elements abundance from [2]. The theoretical gf -values for important (by
the lithium abundance determination) blending lines were especially computed by P. Quinet with the Cowan’s
code as well (see [13]).
RESULTS
Results of the research are presented in Table 2. In the second line, parameters of the model atmospheres used
are given. In Table 2, we give for each star the abundance of Fe I and Fe II in the scale of log N(H) = 12.0,
derived from a group of the Fe I (6102–6103 Å) and Fe II (6149 Å) lines (3rd, 4th lines in the table). The lithium
abundances determined from both 6708 Å and 6103 Å lines and isotopic ratio derived from the 6708 Å line are
shown in 5th–7th lines of the table. Under the solid line, we present the parameters of magnetic field and v sin i
found from the fitting of the Fe II 6149 Å, Pr III 6706.7 Å, and Ca I 6102.7 Å lines. The last value of v sin i was
used for spectra calculations in both lithium lines ranges. The magnetic field parameters from Ca I 6102.7 Å
were used for the 6103 Å range and the ones from Pr III 6707.6 Å – for the 6708 Å range.
CONCLUSIONS
• Our research of two roAp stars, HD 83368 and HD 60435 [12], provides an evidence for the enhanced
lithium abundance near the magnetic field poles. We can expect similar effects in sharp-lined roAp stars.
The high lithium abundance for these stars and the estimates of 6Li/7Li ratio (0.4÷0.5) can be explained
by the Galactic Cosmic Ray (GCR) production due to spallation reactions with ISM in star-forming regions
and the preservation of the original 6Li and 7Li by strong magnetic fields of these stars. The values of
6Li/7Li ratio expected from the GCR production are about 0.5 ÷ 0.8 [5, 16].
• New laboratory and theoretical gf -values for the REE lines are necessary in order to refine our estimates
of the lithium abundance and of the isotopic ratio.
1 [http://www.umh.ac.be/∼astro/dream.shtml]
297
Acknowledgements. The authors are grateful to Dr. P. North for the ESO spectra and Dr. J. Zverko for
the remarks to the manuscript.
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