Determination of atomic abundances of solar-type stars
We discuss the results of abundance determinations of the solar-type stars HD 1835 and HD 10700 using our new procedure. This procedure has the advantage of automated pipeline usage for large amounts of spectroscopic data, with minimal user input. It is based on the spectral synthesis method, where...
Gespeichert in:
| Datum: | 2012 |
|---|---|
| Hauptverfasser: | , , , , , |
| Format: | Artikel |
| Sprache: | English |
| Veröffentlicht: |
Головна астрономічна обсерваторія НАН України
2012
|
| Schriftenreihe: | Advances in Astronomy and Space Physics |
| Online Zugang: | http://dspace.nbuv.gov.ua/handle/123456789/119163 |
| Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Zitieren: | Determination of atomic abundances of solar-type stars / M.G. Malygin, Ya.V. Pavlenko, J.S. Jenkins, H.R.A. Jones, O.M. Ivanyuk, D.J. Pinfield // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 1. — С. 20-22. — Бібліогр.: 12 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-119163 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-1191632017-06-05T03:03:55Z Determination of atomic abundances of solar-type stars Malygin, M.G. Pavlenko, Ya.V. Jenkins, J.S. Jones, H.R.A. Ivanyuk, O.M. Pinfield, D.J. We discuss the results of abundance determinations of the solar-type stars HD 1835 and HD 10700 using our new procedure. This procedure has the advantage of automated pipeline usage for large amounts of spectroscopic data, with minimal user input. It is based on the spectral synthesis method, where the best values are found with our own developed minimization technique. We reduce the number of free parameters in minimization space using the fit to the observed atomic iron lines. We calibrated our procedure using fits to the observed solar spectrum. Then we determined abundances in two solar-type stars, namely the metal-deficient star HD 10700 and the metal-rich star HD 1835. We found good agreement with previously published results. Thus, we aim to use this procedure for the abundance determination of solar-type stars, particularly planet hosting stars, where the knowledge of abundances is crucial for our understanding of their evolution and formation processes. 2012 Article Determination of atomic abundances of solar-type stars / M.G. Malygin, Ya.V. Pavlenko, J.S. Jenkins, H.R.A. Jones, O.M. Ivanyuk, D.J. Pinfield // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 1. — С. 20-22. — Бібліогр.: 12 назв. — англ. 2227-1481 http://dspace.nbuv.gov.ua/handle/123456789/119163 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| description |
We discuss the results of abundance determinations of the solar-type stars HD 1835 and HD 10700 using our new procedure. This procedure has the advantage of automated pipeline usage for large amounts of spectroscopic data, with minimal user input. It is based on the spectral synthesis method, where the best values are found with our own
developed minimization technique. We reduce the number of free parameters in minimization space using the fit to the observed atomic iron lines. We calibrated our procedure using fits to the observed solar spectrum. Then we determined abundances in two solar-type stars, namely the metal-deficient star HD 10700 and the metal-rich star HD 1835. We found good agreement with previously published results. Thus, we aim to use this procedure for the abundance determination of solar-type stars, particularly planet hosting stars, where the knowledge of abundances is crucial for our understanding of their evolution and formation processes. |
| format |
Article |
| author |
Malygin, M.G. Pavlenko, Ya.V. Jenkins, J.S. Jones, H.R.A. Ivanyuk, O.M. Pinfield, D.J. |
| spellingShingle |
Malygin, M.G. Pavlenko, Ya.V. Jenkins, J.S. Jones, H.R.A. Ivanyuk, O.M. Pinfield, D.J. Determination of atomic abundances of solar-type stars Advances in Astronomy and Space Physics |
| author_facet |
Malygin, M.G. Pavlenko, Ya.V. Jenkins, J.S. Jones, H.R.A. Ivanyuk, O.M. Pinfield, D.J. |
| author_sort |
Malygin, M.G. |
| title |
Determination of atomic abundances of solar-type stars |
| title_short |
Determination of atomic abundances of solar-type stars |
| title_full |
Determination of atomic abundances of solar-type stars |
| title_fullStr |
Determination of atomic abundances of solar-type stars |
| title_full_unstemmed |
Determination of atomic abundances of solar-type stars |
| title_sort |
determination of atomic abundances of solar-type stars |
| publisher |
Головна астрономічна обсерваторія НАН України |
| publishDate |
2012 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/119163 |
| citation_txt |
Determination of atomic abundances of solar-type stars / M.G. Malygin, Ya.V. Pavlenko, J.S. Jenkins, H.R.A. Jones, O.M. Ivanyuk, D.J. Pinfield // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 1. — С. 20-22. — Бібліогр.: 12 назв. — англ. |
| series |
Advances in Astronomy and Space Physics |
| work_keys_str_mv |
AT malyginmg determinationofatomicabundancesofsolartypestars AT pavlenkoyav determinationofatomicabundancesofsolartypestars AT jenkinsjs determinationofatomicabundancesofsolartypestars AT joneshra determinationofatomicabundancesofsolartypestars AT ivanyukom determinationofatomicabundancesofsolartypestars AT pinfielddj determinationofatomicabundancesofsolartypestars |
| first_indexed |
2025-07-08T15:21:02Z |
| last_indexed |
2025-07-08T15:21:02Z |
| _version_ |
1837092647390412800 |
| fulltext |
Determination of atomic abundances of solar-type stars
M.G. Malygin1∗, Ya.V. Pavlenko2,3, J. S. Jenkins3,4, H.R.A. Jones3, O.M. Ivanyuk2, D. J. Pin�eld3
Advances in Astronomy and Space Physics, 2, 20-22 (2012)
© M.G. Malygin, Ya.V. Pavlenko, J. S. Jenkins, H.R.A. Jones, O.M. Ivanyuk, D. J. Pin�eld, 2012
1Taras Shevchenko National University of Kyiv, Glushkova ave., 4, 03127, Kyiv, Ukraine
2Main Astronomical Observatory of NAS of Ukraine, Akademika Zabolotnoho St., 27, 03680, Kyiv, Ukraine
3Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hat�eld, Hertfordshire AL10 9AB, UK
4Departamento de Astronomía, Universidad de Chile, Camino del Observatorio 1515, Las Condes, Santiago, Chile
We discuss the results of abundance determinations of the solar-type stars HD1835 and HD10700 using our new
procedure. This procedure has the advantage of automated pipeline usage for large amounts of spectroscopic data,
with minimal user input. It is based on the spectral synthesis method, where the best values are found with our own
developed minimization technique. We reduce the number of free parameters in minimization space using the �t
to the observed atomic iron lines. We calibrated our procedure using �ts to the observed solar spectrum. Then we
determined abundances in two solar-type stars, namely the metal-de�cient star HD10700 and the metal-rich star
HD1835. We found good agreement with previously published results. Thus, we aim to use this procedure for the
abundance determination of solar-type stars, particularly planet hosting stars, where the knowledge of abundances
is crucial for our understanding of their evolution and formation processes.
Key words: stars: abundances; methods: numerical; methods: data analysis
introduction
One of the main reasons for the growing inter-
est to the composition of solar-type stars is that the
atmospheric abundance of planet-hosting stars is an
important factor that a�ects the processes of forma-
tion and evolution of planetary systems.
Reliable sets of physical parameters of the stellar
atmosphere are needed to get accurate abundances
from spectral synthesis �tting: e�ective tempera-
ture, surface gravity, microturbulent velocity, rota-
tional velocity and atomic abundances (see [3, 4]).
the method of calculations
Our procedure is based on the spectra synthesis
method. In the current investigation we used 1D ho-
mogeneous steady-state plane-parallel LTE models
with mixing length approach accounting for convec-
tion. We synthesized spectra in the wavelength range
4000− 9000Å with a step of 0.025Å.
The realisation of the paradigm is a computer
code, developed for the purpose of pipe-line usage
for the determination of abundances in the atmo-
spheres of solar-type stars. The method consists of
three following iterations:
I. Robust determination of log N(Fe)1 in the at-
mosphere of the observed star, with other parame-
ters being �xed. Namely, microturbulent velocity ξt,
e�ective temperature Teff , surface gravity logg and
other atomic abundances log N(X) are �xed to their
�initial guess� user de�ned values. Rotational veloc-
ity v sin i is determined together with log N(Fe) by
our minimization procedure based on �ts to the Fe i
and Fe ii lines.
II. Determination of microturbulent velocity. We
compute a two-dimensional synthetic spectral grid
{log N(Fe), ξt}. log N(Fe) nodes are clustered
around our �rst-iteration value. Again, minimiza-
tion is carried out based on �ts to the selected Fe i
and Fe ii features.
III. Determination of atomic abundances for 7 el-
ements, namely: Si, Ca, Ti, V, Cr, Fe, Ni. All atmo-
sphere parameters are �xed to their obtained values.
A 1D synthetic spectra grid is computed for di�erent
log N(X) values for each atom. All other parameters
are �xed. Again, minimization is carried out based
on �ts to the selected atomic lines.
On each iteration we recompute the model atmo-
sphere and synthetic spectra for current values of the
parameters. This provides a fast convergence in the
framework of self-consistency and makes possible the
subsequent reduction of �free� parameters. At last,
only one non-�xed parameter is left, which is the re-
quired atomic abundance itself.
All calculations were carried out with our own
∗kolkosm@ukr.net
1Here N(Fe) is the relative amount of Fe atoms as referred to the total atomic amount: N(X) = number density of X atoms/total number
density = n(Fe)/ntot, ntot =
P
X n(X). In this frame N(H) ≈ 0.9 and the sum of all relative amounts are equal to unity: PX N(X) = 1 [2].
20
Advances in Astronomy and Space Physics M.G. Malygin et al.
software: SAM12 for atmospheric modelling, WITA6
for spectra synthesis, FITA2 for the minimization
[4, 8, 9, 11].
Line-lists for the 7 neutral atoms listed above,
along with Tiii and Feii were compiled. For this
purpose we used the Vienna Atomic Lines Database
VALD 2 [7]. For each atom we synthesized its ab-
sorption spectra in the solar atmosphere. We then
selected spectral features with central residual �uxes
of rc < 0.8. From this set we excluded those severely
a�ected with strong nearby blends. We further ac-
counted for blends by choosing a speci�c wavelength
range for each line, where it �ts well the observed
solar spectrum [6]. Finally, we used the selected list
of wavelength ranges to calculate minimization pa-
rameters (see below) to get abundances. Those fea-
tures that provide incorrect solar abundances were
excluded from the list also. After several such iter-
ations we composed reliable lists of atomic features
together with corresponding wavelength ranges for 9
ions. We used [2] as a reference for our abundance
measurements. We note that more elements could
be added into the analysis as soon as more robust
atomic data is provided.
We introduce the following minimization param-
eter:
S =
∑
ν
(1− rsν/roν)
2/N, (1)
so the minimum Smin = min
1..N
{S} determines the
best solution for any given line from the preselected
set. Here N is the total dimension of the synthetic
spectra grid, roν & rsν are the normalized �uxes in
the observed and computed spectra, respectively. ν
runs through the narrow speci�ed wavelength range
across the features core. We adjusted 0.05 dex for
the abundance step and set N = 30 in the current
investigation. For each line from the list, S is calcu-
lated and its minimum is found for a certain abun-
dance. Treating this sample as a set of independent
measurements of the respective atomic abundance,
we formally introduced mean standard deviation:
σX =
√∑
i(X−Xi)2
Nl(Nl − 1)
, (2)
where X = log N(X), Nl is a number of lines in the
list. We also introduced standard deviation σ0 for
Smin parameter:
σ0 =
√ ∑
j(Smin − Sj
min)
2
Nl(Nl − 1)
, (3)
where Sj
min is a minimization parameter calculated
for j line for the grid node {ξ∗t , log N(Fe)∗}, which
refers to S minimum. Nl is a number of lines in
the list. Furthermore, the required abundances were
averaged within this 1-σ0 range with an inverse vari-
ance weighting scheme:
log N(X) =
∑
(log Ni(X)/σi)
/ ∑
(1/σi), (4)
where i runs through those values, which placed S
into Smin ± σ0 range. Such weighting was done for
other determined parameters as well.
results and conclusions
We have developed a procedure for �nding atomic
abundances in solar-type atmospheres within a frame
of a self-consistent approach. We developed this pro-
cedure into a computer code, easily operated by a
user with various shell-scripts. We built atomic line-
lists and complementary lists of speci�c wavelength
ranges for 9 ions that provide a robust abundance
determination for the observed solar spectrum. Ta-
ble 1 represents the numbers of these carefully se-
lected lines for each ion.
Fe i and Fe ii lines were used to determine the so-
lar atmosphere parameters. Two panels in Figure 1
show clear minima of the minimization parameter
in two-dimensional parameter space. When carrying
out the minimization with Feii lines, the minimum
is less pronounced, but still noticeable. The plots
present the results from the second iteration, and we
can �nd that the �nal result does not di�er much
from this one.
We measured the abundances of two solar-type
stars: the metal-de�cient star HD10700 and the
metal-rich star HD1835. The spectra were obtained
with the Fibre-fed Extended Range Optical Spectro-
graph (FEROS) mounted on the MPG/ESO � 2.2m
telescope on the La Silla site in Chile [3]. S/N ra-
tios of ∼ 200 were achieved over most of the op-
tical domain at the operating resolution of FEROS
(R ∼ 46000), which is more than su�cient for accu-
rate stellar abundance work. The results presented
in Table 2 are consistent with previous investigations
(see e.g. [1, 2, 12]).
Thus, we claim that the developed procedure and
computer code allow us to determine atomic abun-
dances, microturbulent velocities and rotational ve-
locities in stellar atmospheres in the framework of a
self consistent approach. Furthermore, we �nd our
solution to be comparatively stable in respect to the
small variations of the main input parameters: Teff ,
logg and log N(Fe) [10]. This developed computer
code will be involved in the processing of consider-
able data sets of solar-type stellar spectroscopic ob-
servations e. g. [5].
acknowledgement
We acknowledge funding by EU PF7 Marie Curie
Initial Training Networks (ITN) ROPACS project
(GA N 213646). MM thanks to his wife LT for
her unappreciative support and to BG for providing
21
Advances in Astronomy and Space Physics M.G. Malygin et al.
Fig. 1: Minimization parameter S as a function of iron abundance and microturbulent velocity in the atmosphere of
the Sun. Left panel refers to Fei line-list. Right panel refers to Feii line-list. We show 1-, 2-, 3-σ levels as contour
plots. The positions of Smin is marked with + and its σ0-averaged position is marked with X (see equation 4).
The following values correspond to σ0-averaged values: log N(Fe) = 4.426 ± 0.025 dex, ξt = 1.0 km/s for Fei lines,
left panel; log N(Fe) = 4.407 ± 0.041 dex, ξt = 0.8 km/s for Feii lines, right panel. Ranges of iron abundance and
microturbulent velocity on the plots are those 2D synthetic spectra grid was computed for. There were 9× 7 nodes
in {log N(Fe), ξt} parameter space on the second iteration.
Table 1: Number of lines in the composed atomic line-lists.
element Si i Ca i Ti i Ti ii V I Cr i Fe i Fe ii Ni i
Nl 4 16 30 27 54 54 132 24 52
Table 2: Abundances for HD10700, the Sun and HD1835. log N(X) in dex, mean values correspond to formula 4,
errors are one-σ errors (see formula 2). The �rst column labels the atomic ion.
HD10700 The Sun HD1835
Ca i −6.018± 0.018 −5.48± 0.03 −5.39± 0.03
Cr i −6.975± 0.010 −6.303± 0.016 −6.098± 0.022
Fe i −5.065± 0.009 −4.414± 0.010 −4.237± 0.010
Fe ii −5.123± 0.023 −4.41± 0.05 −4.23± 0.04
Ni i −6.363± 0.014 −5.753± 0.012 −5.608± 0.012
Si i −4.705± 0.025 −4.30± 0.05 −4.21± 0.05
Ti i −7.498± 0.025 −7.102± 0.029 −6.90± 0.04
Ti ii −7.448± 0.025 −7.080± 0.027 −6.83± 0.05
V i −8.23± 0.08 −7.88± 0.11 −7.81± 0.17
thoroughgoing understanding of the related physi-
cal processes. JSJ acknowledges funding by Fonde-
cyt through grant 3110004 and partial support from
Centro de Astro�sica FONDAP 15010003, the Gem-
ini CONICYT fund and the Comite Mixto ESO-
Gobierno de Chile. We thank to anonymous referee
for valuable suggestions that improved the quality of
this article.
references
[1] Grevesse N. & Anders E. 1989, Geochim. Cos-
mochim. Acta, 53, 197
[2] Gurtovenko E.A. & Kostyk R. I. 1989, `Fraunhofer spec-
trum and a system of solar oscillator strengths', Nauk.
dumka, Kiev
[3] Jenkins J. S., Jones H.R.A., Pavlenko Ya.V. et al. 2008,
A&A, 485, 571
[4] Jenkins J. S., Ramsey L.W., Jones H.R.A. et al. 2009,
ApJ, 704, 975
[5] Jenkins J. S., Murgas F., Rojo P. et al. 2008, 531, id.A8
[6] Kurucz R. L., Furenlid I., Brault J. & Testerman L. 1984,
`Solar �ux atlas from 296 to 1300 nm', National Solar
Observatory, New Mexico
[7] Kupka F., Piskunov N., Ryabchikova T.A. Stem-
pels H.C. & Weiss W.W. 1999, A&AS, 138, 119
[8] Pavlenko Ya.V. 2000, Astron. Rep., 44, 219
[9] Pavlenko Ya.V. 2000, Astron. Rep., 47, 59
[10] Pavlenko Ya.V., Jenkins J. S., Jones H.R.A.,
Ivanyuk O. & Pin�eld D. J. 2012, (to appear in
MNRAS) [arXiv:1201.5099]
[11] Pavlenko Ya.V. & Yakovina L.A. 2009, Kinematika i
Fizika Nebesnykh Tel, 25, 6, 452
[12] Valenti J. A. & Fischer D.A. ApJS, 159, 141
22
|