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ADS astronomy entries on 2022-09-14
author:"Barklem, Paul S."
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Title: The Gaia-ESO Public Spectroscopic Survey: Motivation,
implementation, GIRAFFE data processing, analysis, and final data
products
Authors: Gilmore, G.; Randich, S.; Worley, C. C.; Hourihane, A.;
Gonneau, A.; Sacco, G. G.; Lewis, J. R.; Magrini, L.; Francois, P.;
Jeffries, R. D.; Koposov, S. E.; Bragaglia, A.; Alfaro, E. J.; Allende
Prieto, C.; Blomme, R.; Korn, A. J.; Lanzafame, A. C.; Pancino, E.;
Recio-Blanco, A.; Smiljanic, R.; Van Eck, S.; Zwitter, T.; Bensby, T.;
Flaccomio, E.; Irwin, M. J.; Franciosini, E.; Morbidelli, L.; Damiani,
F.; Bonito, R.; Friel, E. D.; Vink, J. S.; Prisinzano, L.; Abbas,
U.; Hatzidimitriou, D.; Held, E. V.; Jordi, C.; Paunzen, E.; Spagna,
A.; Jackson, R. J.; Maiz Apellaniz, J.; Asplund, M.; Bonifacio, P.;
Feltzing, S.; Binney, J.; Drew, J.; Ferguson, A. M. N.; Micela, G.;
Negueruela, I.; Prusti, T.; Rix, H. -W.; Vallenari, A.; Bergemann,
M.; Casey, A. R.; de Laverny, P.; Frasca, A.; Hill, V.; Lind, K.;
Sbordone, L.; Sousa, S. G.; Adibekyan, V.; Caffau, E.; Daflon, S.;
Feuillet, D. K.; Gebran, M.; Gonzalez Hernandez, J. I.; Guiglion,
G.; Herrero, A.; Lobel, A.; Merle, T.; Mikolaitis, S.; Montes, D.;
Morel, T.; Ruchti, G.; Soubiran, C.; Tabernero, H. M.; Tautvaisiene,
G.; Traven, G.; Valentini, M.; Van der Swaelmen, M.; Villanova, S.;
Viscasillas Vazquez, C.; Bayo, A.; Biazzo, K.; Carraro, G.; Edvardsson,
B.; Heiter, U.; Jofre, P.; Marconi, G.; Martayan, C.; Masseron, T.;
Monaco, L.; Walton, N. A.; Zaggia, S.; Aguirre Borsen-Koch, V.; Alves,
J.; Balaguer-Nunez, L.; Barklem, P. S.; Barrado, D.; Bellazzini, M.;
Berlanas, S. R.; Binks, A. S.; Bressan, A.; Capuzzo-Dolcetta, R.;
Casagrande, L.; Casamiquela, L.; Collins, R. S.; D'Orazi, V.; Dantas,
M. L. L.; Debattista, V. P.; Delgado-Mena, E.; Di Marcantonio, P.;
Drazdauskas, A.; Evans, N. W.; Famaey, B.; Franchini, M.; Fremat, Y.;
Fu, X.; Geisler, D.; Gerhard, O.; Gonzalez Solares, E. A.; Grebel,
E. K.; Gutierrez Albarran, M. L.; Jimenez-Esteban, F.; Jonsson, H.;
Khachaturyants, T.; Kordopatis, G.; Kos, J.; Lagarde, N.; Ludwig,
H. -G.; Mahy, L.; Mapelli, M.; Marfil, E.; Martell, S. L.; Messina,
S.; Miglio, A.; Minchev, I.; Moitinho, A.; Montalban, J.; Monteiro,
M. J. P. F. G.; Morossi, C.; Mowlavi, N.; Mucciarelli, A.; Murphy,
D. N. A.; Nardetto, N.; Ortolani, S.; Paletou, F.; Palous, J.;
Pickering, J. C.; Quirrenbach, A.; Re Fiorentin, P.; Read, J. I.;
Romano, D.; Ryde, N.; Sanna, N.; Santos, W.; Seabroke, G. M.; Spina,
L.; Steinmetz, M.; Stonkute, E.; Sutorius, E.; Thevenin, F.; Tosi,
M.; Tsantaki, M.; Wright, N.; Wyse, R. F. G.; Zoccali, M.; Zorec,
J.; Zucker, D. B.
2022arXiv220805432G Altcode:
The Gaia-ESO Public Spectroscopic Survey is an ambitious project
designed to obtain astrophysical parameters and elemental abundances
for 100,000 stars, including large representative samples of the
stellar populations in the Galaxy, and a well-defined sample of 60
(plus 20 archive) open clusters. We provide internally consistent
results calibrated on benchmark stars and star clusters, extending
across a very wide range of abundances and ages. This provides a
legacy data set of intrinsic value, and equally a large wide-ranging
dataset that is of value for homogenisation of other and future
stellar surveys and Gaia's astrophysical parameters. This article
provides an overview of the survey methodology, the scientific aims,
and the implementation, including a description of the data processing
for the GIRAFFE spectra. A companion paper (arXiv:2206.02901)
introduces the survey results. Gaia-ESO aspires to quantify both
random and systematic contributions to measurement uncertainties. Thus
all available spectroscopic analysis techniques are utilised, each
spectrum being analysed by up to several different analysis pipelines,
with considerable effort being made to homogenise and calibrate the
resulting parameters. We describe here the sequence of activities up to
delivery of processed data products to the ESO Science Archive Facility
for open use. The Gaia-ESO Survey obtained 202,000 spectra of 115,000
stars using 340 allocated VLT nights between December 2011 and January
2018 from GIRAFFE and UVES. The full consistently reduced final data set
of spectra was released through the ESO Science Archive Facility in late
2020, with the full astrophysical parameters sets following in 2022.
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Title: The Gaia-ESO Public Spectroscopic Survey: Implementation,
data products, open cluster survey, science, and legacy
Authors: Randich, S.; Gilmore, G.; Magrini, L.; Sacco, G. G.; Jackson,
R. J.; Jeffries, R. D.; Worley, C. C.; Hourihane, A.; Gonneau, A.;
Viscasillas Vàzquez, C.; Franciosini, E.; Lewis, J. R.; Alfaro, E. J.;
Allende Prieto, C.; Blomme, T. Bensby R.; Bragaglia, A.; Flaccomio, E.;
François, P.; Irwin, M. J.; Koposov, S. E.; Korn, A. J.; Lanzafame,
A. C.; Pancino, E.; Recio-Blanco, A.; Smiljanic, R.; Van Eck, S.;
Zwitter, T.; Asplund, M.; Bonifacio, P.; Feltzing, S.; Binney, J.;
Drew, J.; Ferguson, A. M. N.; Micela, G.; Negueruela, I.; Prusti,
T.; Rix, H. -W.; Vallenari, A.; Bayo, A.; Bergemann, M.; Biazzo, K.;
Carraro, G.; Casey, A. R.; Damiani, F.; Frasca, A.; Heiter, U.; Hill,
V.; Jofré, P.; de Laverny, P.; Lind, K.; Marconi, G.; Martayan, C.;
Masseron, T.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sbordone,
L.; Sousa, S. G.; Zaggia, S.; Adibekyan, V.; Bonito, R.; Caffau,
E.; Daflon, S.; Feuillet, D. K.; Gebran, M.; González Hernández,
J. I.; Guiglion, G.; Herrero, A.; Lobel, A.; Maíz Apellániz,
J.; Merle, T.; Mikolaitis, S.; Montes, D.; Morel, T.; Soubiran,
C.; Spina, L.; Tabernero, H. M.; Tautvaišienė, G.; Traven, G.;
Valentini, M.; Van der Swaelmen, M.; Villanova, S.; Wright, N. J.;
Abbas, U.; Aguirre Børsen-Koch, V.; Alves, J.; Balaguer-Núnez,
L.; Barklem, P. S.; Barrado, D.; Berlanas, S. R.; Binks, A. S.;
Bressan, A.; Capuzzo--Dolcetta, R.; Casagrande, L.; Casamiquela, L.;
Collins, R. S.; D'Orazi, V.; Dantas, M. L. L.; Debattista, V. P.;
Delgado-Mena, E.; Di Marcantonio, P.; Drazdauskas, A.; Evans, N. W.;
Famaey, B.; Franchini, M.; Frémat, Y.; Friel, E. D.; Fu, X.; Geisler,
D.; Gerhard, O.; González Solares, E. A.; Grebel, E. K.; Gutiérrez
Albarrán, M. L.; Hatzidimitriou, D.; Held, E. V.; Jiménez-Esteban,
F.; Jönsson, H.; Jordi, C.; Khachaturyants, T.; Kordopatis, G.; Kos,
J.; Lagarde, N.; Mahy, L.; Mapelli, M.; Marfil, E.; Martell, S. L.;
Messina, S.; Miglio, A.; Minchev, I.; Moitinho, A.; Montalban, J.;
Monteiro, M. J. P. F. G.; Morossi, C.; Mowlavi, N.; Mucciarelli, A.;
Murphy, D. N. A.; Nardetto, N.; Ortolani, S.; Paletou, F.; Palouus, J.;
Paunzen, E.; Pickering, J. C.; Quirrenbach, A.; Re Fiorentin, P.; Read,
J. I.; Romano, D.; Ryde, N.; Sanna, N.; Santos, W.; Seabroke, G. M.;
Spagna, A.; Steinmetz, M.; Stonkuté, E.; Sutorius, E.; Thévenin,
F.; Tosi, M.; Tsantaki, M.; Vink, J. S.; Wright, N.; Wyse, R. F. G.;
Zoccali, M.; Zorec, J.; Zucker, D. B.; Walton, N. A.
2022arXiv220602901R Altcode:
In the last 15 years different ground-based spectroscopic surveys
have been started (and completed) with the general aim of delivering
stellar parameters and elemental abundances for large samples of
Galactic stars, complementing Gaia astrometry. Among those surveys,
the Gaia-ESO Public Spectroscopic Survey (GES), the only one performed
on a 8m class telescope, was designed to target 100,000 stars using
FLAMES on the ESO VLT (both Giraffe and UVES spectrographs), covering
all the Milky Way populations, with a special focus on open star
clusters. This article provides an overview of the survey implementation
(observations, data quality, analysis and its success, data products,
and releases), of the open cluster survey, of the science results and
potential, and of the survey legacy. A companion article (Gilmore et
al.) reviews the overall survey motivation, strategy, Giraffe pipeline
data reduction, organisation, and workflow. The GES has determined
homogeneous good-quality radial velocities and stellar parameters for a
large fraction of its more than 110,000 unique target stars. Elemental
abundances were derived for up to 31 elements for targets observed with
UVES. Lithium abundances are delivered for about 1/3 of the sample. The
analysis and homogenisation strategies have proven to be successful;
several science topics have been addressed by the Gaia-ESO consortium
and the community, with many highlight results achieved. The final
catalogue has been released through the ESO archive at the end of
May 2022, including the complete set of advanced data products. In
addition to these results, the Gaia-ESO Survey will leave a very
important legacy, for several aspects and for many years to come.
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Title: Non-LTE abundance corrections for late-type stars from 2000Å
to 3{\mu}m: I. Na, Mg, and Al
Authors: Lind, K.; Nordlander, T.; Wehrhahn, A.; Montelius, M.;
Osorio, Y.; Barklem, P. S.; Afsar, M.; Sneden, C.; Kobayashi, C.
2022arXiv220611070L Altcode:
It is well known that cool star atmospheres depart from local
thermodynamic equilibrium (LTE). Accurate abundance determination
requires taking those effects into account, but the necessary non-LTE
calculations are often lacking. Our goal is to provide detailed
estimates of NLTE effects for FGK type stars for all spectral lines
from the ultraviolet to the infrared that are potentially useful
as abundance diagnostics. The first paper in this series focusses
on the light elements Na, Mg and Al. The code PySME is used to
compute curves-of-growth for 2158 MARCS model atmospheres in a wide
parameter range. Nine abundance points are used to construct individual
line curves-of-growth by calculating the equivalent widths of 35 Na
lines, 134 Mg lines, and 34 Al lines. The lines are selected from the
ultra-violet to the near infrared wavelength range. We demonstrate the
power of the new grids with LTE and NLTE abundance analysis by means
of equivalent width measurements of five benchmark stars; the Sun,
Arcturus, HD84937, HD140283 and HD122563. For Na, the NLTE abundances
are lower than in LTE and show markedly reduced line-to-line scatter
in the metal-poor stars. For Mg, we confirm previous reports of a
significant 0.25 dex LTE ionization imbalance in metal-poor stars that
is only slightly improved in NLTE (0.18 dex). LTE abundances based on Mg
II lines agree better with models of Galactic chemical evolution. For
Al, NLTE calculations strongly reduce a 0.6 dex ionization imbalance
seen in LTE for the metal-poor stars. The abundance corrections
presented in this work are in good agreement with previous studies for
the subset of lines that overlap, except for strongly saturated lines.
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Title: The molecular chemistry of Type Ibc supernovae, and diagnostic
potential with the James Webb Space Telescope
Authors: Liljegren, S.; Jerkstrand, A.; Barklem, P. S.; Nyman, G.;
Brady, R.; Yurchenko, S. N.
2022arXiv220307021L Altcode:
A currently unsolved question in supernova research is the origin of
stripped-envelope supernovae (SESNe). Such SNe lack spectral signatures
of hydrogen (Type Ib), or hydrogen and helium (Type Ic), indicating that
the outer stellar layers have been stripped during their evolution. The
mechanism for this is not well understood, and to disentangle the
different scenarios determination of nucleosynthesis yields from
observed spectra can be attempted. However, the interpretation of
observations depends on the adopted spectral models. A previously
missing ingredient in these is the inclusion of molecular effects, which
can be significant. We aim to investigate how the molecular chemistry in
stripped-envelope supernovae affects physical conditions and optical
spectra and produces ro-vibrational emission in the mid-infrared
(MIR). We also aim to assess the diagnostic potential of observations
of such MIR emission with JWST. We couple a chemical kinetic network
including carbon, oxygen, silicon, and sulfur-bearing molecules into
the NLTE spectral synthesis code SUMO. We let four species - CO, SiO,
SiS and SO - participate in the NLTE cooling of the gas to achieve
self-consistency between the molecule formation and the temperature. We
apply the new framework to model the spectrum of a Type Ic supernova
in the 100-600d time range. Molecules are predicted to form in SESN
ejecta in significant quantities (typical mass $10^{-3}$ $M_\odot$)
throughout the 100-600d interval. The impact on the temperature
and optical emission depends on the density of the oxygen zones and
varies with epoch. For example, the [O I] 6300, 6364 feature can be
quenched by molecules from 200 to 450d depending on density. The MIR
predictions show strong emission in the fundamental bands of CO, SiO,
and SiS, and in the CO and SiO overtones.
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Title: Correspondence between the surface integral and linear
combination of atomic orbitals methods for ionic-covalent interactions
in mutual neutralisation processes involving H$^-$/D$^-$
Authors: Barklem, Paul S.
2021arXiv211204991B Altcode:
The surface integral method for estimating ionic-covalent interactions
in diatomic systems been successful in producing cross sections for
mutual neutralisation (MN) in reasonable agreement with experimental
results for branching fractions between final states in systems
such as O$^+$/O$^-$ and N$^+$/O$^-$. However, for simpler cases of
MN involving H$^-$ or D$^-$, such as Li$^+$/D$^-$ and Na$^+$/D$^-$,
it has not produced results that are in agreement with experiments
and other theoretical calculations; in particular, for Li$^+$/D$^-$
calculations predict the wrong ordering of importance of final channels,
including the incorrect most populated channel. The reason for this
anomaly is investigated and a leading constant to the asymptotic
H$^-$ wavefunction is found that is different by roughly a factor
$1/\sqrt{2}$ to that which has been used in previous calculations
with the surface integral method involving H$^-$ or D$^-$. With this
correction, far better agreement with both experimental results and with
calculations with full quantum and LCAO methods is obtained. Further,
it is shown that the surface integral method and LCAO methods have
the same asymptotic behaviour, in contrast to previous claims. This
result suggests the surface integral method, which is comparatively
easy to calculate, has greater potential for estimating MN processes
than earlier comparisons had suggested.
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Title: Diagnostic capabilities of spectropolarimetric observations for
understanding solar phenomena. I. Zeeman-sensitive photospheric lines
Authors: Quintero Noda, C.; Barklem, P. S.; Gafeira, R.; Ruiz Cobo,
B.; Collados, M.; Carlsson, M.; Martínez Pillet, V.; Orozco Suárez,
D.; Uitenbroek, H.; Katsukawa, Y.
2021A&A...652A.161Q Altcode: 2021arXiv210605084Q
Future ground-based telescopes will expand our capabilities for
simultaneous multi-line polarimetric observations in a wide range of
wavelengths, from the near-ultraviolet to the near-infrared. This
creates a strong demand to compare candidate spectral lines to
establish a guideline of the lines that are most appropriate for each
observation target. We focused in this first work on Zeeman-sensitive
photospheric lines in the visible and infrared. We first examined their
polarisation signals and response functions using a 1D semi-empirical
atmosphere. Then we studied the spatial distribution of the line core
intensity and linear and circular polarisation signals using a realistic
3D numerical simulation. We ran inversions of synthetic profiles, and
we compared the heights at which we obtain a high correlation between
the input and the inferred atmosphere. We also used this opportunity
to revisit the atomic information we have on these lines and computed
the broadening cross-sections due to collisions with neutral hydrogen
atoms for all the studied spectral lines. The results reveal that
four spectral lines stand out from the rest for quiet-Sun and network
conditions: Fe I 5250.2, 6302, 8468, and 15 648 Å. The first three
form higher in the atmosphere, and the last line is mainly sensitive to
the atmospheric parameters at the bottom of the photosphere. However,
as they reach different heights, we strongly recommend using at least
one of the first three candidates together with the Fe I 15 648 Å line
to optimise our capabilities for inferring the thermal and magnetic
properties of the lower atmosphere.
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Title: Mutual Neutralization in
Li<SUP>+</SUP>+H<SUP>-</SUP>/D<SUP>-</SUP> and
Na<SUP>+</SUP>+H<SUP>-</SUP>/D<SUP>-</SUP> Collisions: Implications
of Experimental Results for Non-LTE Modeling of Stellar Spectra
Authors: Barklem, Paul S.; Amarsi, Anish M.; Grumer, Jon; Eklund,
Gustav; Rosén, Stefan; Ji, MingChao; Cederquist, Henrik; Zettergren,
Henning; Schmidt, Henning T.
2021ApJ...908..245B Altcode: 2020arXiv201211968B
Advances in merged-beams instruments have allowed experimental studies
of the mutual neutralization (MN) processes in collisions of both
Li<SUP>+</SUP> and Na<SUP>+</SUP> ions with D<SUP>-</SUP> at energies
below 1 eV. These experimental results place constraints on theoretical
predictions of MN processes of Li<SUP>+</SUP> and Na<SUP>+</SUP> with
H<SUP>-</SUP>, important for non-LTE modeling of Li and Na spectra in
late-type stars. We compare experimental results with calculations
for methods typically used to calculate MN processes, namely the
full quantum (FQ) approach, and asymptotic model approaches based on
the linear combination of atomic orbitals (LCAO) and semiempirical
(SE) methods for deriving couplings. It is found that FQ calculations
compare best overall with the experiments, followed by the LCAO, and the
SE approaches. The experimental results together with the theoretical
calculations, allow us to investigate the effects on modeled spectra and
derived abundances and their uncertainties arising from uncertainties
in the MN rates. Numerical experiments in a large grid of 1D model
atmospheres, and a smaller set of 3D models, indicate that neglect of
MN can lead to abundance errors of up to 0.1 dex (26%) for Li at low
metallicity, and 0.2 dex (58%) for Na at high metallicity, while the
uncertainties in the relevant MN rates as constrained by experiments
correspond to uncertainties in abundances of much less than 0.01 dex
(2%). This agreement for simple atoms gives confidence in the FQ, LCAO,
and SE model approaches to be able to predict MN with the accuracy
required for non-LTE modeling in stellar atmospheres.
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Title: Atomic data for the Gaia-ESO Survey
Authors: Heiter, U.; Lind, K.; Bergemann, M.; Asplund, M.; Mikolaitis,
Š.; Barklem, P. S.; Masseron, T.; de Laverny, P.; Magrini, L.;
Edvardsson, B.; Jönsson, H.; Pickering, J. C.; Ryde, N.; Bayo Arán,
A.; Bensby, T.; Casey, A. R.; Feltzing, S.; Jofré, P.; Korn, A. J.;
Pancino, E.; Damiani, F.; Lanzafame, A.; Lardo, C.; Monaco, L.;
Morbidelli, L.; Smiljanic, R.; Worley, C.; Zaggia, S.; Randich, S.;
Gilmore, G. F.
2021A&A...645A.106H Altcode: 2020arXiv201102049H
Context. We describe the atomic and molecular data that were used for
the abundance analyses of FGK-type stars carried out within the Gaia-ESO
Public Spectroscopic Survey in the years 2012 to 2019. The Gaia-ESO
Survey is one among several current and future stellar spectroscopic
surveys producing abundances for Milky-Way stars on an industrial
scale. <BR /> Aims: We present an unprecedented effort to create a
homogeneous common line list, which was used by several abundance
analysis groups using different radiative transfer codes to calculate
synthetic spectra and equivalent widths. The atomic data are accompanied
by quality indicators and detailed references to the sources. The
atomic and molecular data are made publicly available at the CDS. <BR
/> Methods: In general, experimental transition probabilities were
preferred but theoretical values were also used. Astrophysical gf-values
were avoided due to the model-dependence of such a procedure. For
elements whose lines are significantly affected by a hyperfine structure
or isotopic splitting, a concerted effort has been made to collate the
necessary data for the individual line components. Synthetic stellar
spectra calculated for the Sun and Arcturus were used to assess
the blending properties of the lines. We also performed adetailed
investigation of available data for line broadening due to collisions
with neutral hydrogen atoms. <BR /> Results: Among a subset of over
1300 lines of 35 elements in the wavelength ranges from 475 to 685 nm
and from 850 to 895 nm, we identified about 200 lines of 24 species
which have accurate gf-values and are free of blends in the spectra of
the Sun and Arcturus. For the broadening due to collisions with neutral
hydrogen, we recommend data based on Anstee-Barklem-O'Mara theory, where
possible. We recommend avoiding lines of neutral species for which these
are not available. Theoretical broadening data by R.L. Kurucz should
be used for Sc II, Ti II, and Y II lines; additionally, for ionised
rare-earth species, the Unsöld approximation with an enhancement
factor of 1.5 for the line width can be used. <BR /> Conclusions: The
line list has proven to be a useful tool for abundance determinations
based on the spectra obtained within the Gaia-ESO Survey, as well as
other spectroscopic projects. Accuracies below 0.2 dex are regularly
achieved, where part of the uncertainties are due to differences in
the employed analysis methods. Desirable improvements in atomic data
were identified for a number of species, most importantly Al I, S I,
and Cr II, but also Na I, Si I, Ca II, and Ni I. <P />The atomic and
molecular data are only available at the CDS via an anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/645/A106">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/645/A106</A>
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Title: The GALAH Survey: non-LTE departure coefficients for large
spectroscopic surveys
Authors: Amarsi, A. M.; Lind, K.; Osorio, Y.; Nordlander, T.;
Bergemann, M.; Reggiani, H.; Wang, E. X.; Buder, S.; Asplund, M.;
Barklem, P. S.; Wehrhahn, A.; Skúladóttir, Á.; Kobayashi, C.;
Karakas, A. I.; Gao, X. D.; Bland-Hawthorn, J.; de Silva, G. M.; Kos,
J.; Lewis, G. F.; Martell, S. L.; Sharma, S.; Simpson, J. D.; Zucker,
D. B.; Čotar, K.; Horner, J.; GALAH Collaboration
2020A&A...642A..62A Altcode: 2020arXiv200809582A
Massive sets of stellar spectroscopic observations are rapidly becoming
available and these can be used to determine the chemical composition
and evolution of the Galaxy with unprecedented precision. One of the
major challenges in this endeavour involves constructing realistic
models of stellar spectra with which to reliably determine stellar
abundances. At present, large stellar surveys commonly use simplified
models that assume that the stellar atmospheres are approximately
in local thermodynamic equilibrium (LTE). To test and ultimately
relax this assumption, we have performed non-LTE calculations for
13 different elements (H, Li, C, N, O, Na, Mg, Al, Si, K, Ca, Mn,
and Ba), using recent model atoms that have physically-motivated
descriptions for the inelastic collisions with neutral hydrogen,
across a grid of 3756 1D MARCS model atmospheres that spans 3000 ≤
T<SUB>eff</SUB>/K ≤ 8000, - 0.5 ≤log g/cm s<SUP>-2</SUP> ≤ 5.5,
and - 5 ≤ [Fe/H] ≤ 1. We present the grids of departure coefficients
that have been implemented into the GALAH DR3 analysis pipeline in
order to complement the extant non-LTE grid for iron. We also present
a detailed line-by-line re-analysis of 50 126 stars from GALAH DR3. We
found that relaxing LTE can change the abundances by between - 0.7 dex
and + 0.2 dex for different lines and stars. Taking departures from
LTE into account can reduce the dispersion in the [A/Fe] versus [Fe/H]
plane by up to 0.1 dex, and it can remove spurious differences between
the dwarfs and giants by up to 0.2 dex. The resulting abundance slopes
can thus be qualitatively different in non-LTE, possibly with important
implications for the chemical evolution of our Galaxy. The grids of
departure coefficients are publicly available and can be implemented
into LTE pipelines to make the most of observational data sets from
large spectroscopic surveys. <P />Grids of departure coefficients can
be found online (<xref ref-type="bibr" rid="R3">http://Amarsi
2020</xref>http://) or by contacting the lead author directly.
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Title: Gaia Data Release 2. The kinematics of globular clusters and
dwarf galaxies around the Milky Way (Corrigendum)
Authors: Gaia Collaboration; Helmi, A.; van Leeuwen, F.; McMillan,
P. J.; Massari, D.; Antoja, T.; Robin, A. C.; Lindegren, L.;
Bastian, U.; Arenou, F.; Babusiaux, C.; Biermann, M.; Breddels,
M. A.; Hobbs, D.; Jordi, C.; Pancino, E.; Reylé, C.; Veljanoski,
J.; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne,
J. H. J.; Bailer-Jones, C. A. L.; Evans, D. W.; Eyer, L.; Jansen,
F.; Klioner, S. A.; Lammers, U.; Luri, X.; Mignard, F.; Panem,
C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.;
Soubiran, C.; Walton, N. A.; Cropper, M.; Drimmel, R.; Katz, D.;
Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castañeda, J.; Chaoul,
L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra, R.; Holl, B.;
Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Panuzzo,
P.; Portell, J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thévenin,
F.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Teyssier,
D.; Altmann, M.; Andrae, R.; Audard, M.; Bellas-Velidis, I.; Benson,
K.; Berthier, J.; Blomme, R.; Burgess, P.; Busso, G.; Carry, B.;
Cellino, A.; Clementini, G.; Clotet, M.; Creevey, O.; Davidson,
M.; De Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.;
Fernández-Hernández, J.; Fouesneau, M.; Frémat, Y.; Galluccio, L.;
García-Torres, M.; González-Núñez, J.; González-Vidal, J. J.;
Gosset, E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison,
D. L.; Hernández, J.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.;
Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.;
Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.; Löffler, W.;
Manteiga, M.; Marrese, P. M.; Martín-Fleitas, J. M.; Moitinho, A.;
Mora, A.; Muinonen, K.; Osinde, J.; Pauwels, T.; Petit, J. -M.;
Recio-Blanco, A.; Richards, P. J.; Rimoldini, L.; Sarro, L. M.;
Siopis, C.; Smith, M.; Sozzetti, A.; Süveges, M.; Torra, J.; van
Reeven, W.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts, C.;
Altavilla, G.; Álvarez, M. A.; Alvarez, R.; Alves, J.; Anderson,
R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Arcay, B.;
Astraatmadja, T. L.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.;
Balm, P.; Barache, C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem,
P. S.; Barrado, D.; Barros, M.; Barstow, M. A.; Bartholomé Muñoz,
S.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.; Berihuete, A.;
Bertone, S.; Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.; Boch,
T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bossini, D.; Bouquillon,
S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Bressan, A.; Brouillet,
N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli, B.; Burlacu, A.;
Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau, E.; Cancelliere,
R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo, R.; Carlucci, T.;
Carrasco, J. M.; Casamiquela, L.; Castellani, M.; Castro-Ginard, A.;
Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza, G.; Costigan, G.;
Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypers, J.; Dafonte,
C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; de Laverny,
P.; De Luise, F.; De March, R.; de Martino, D.; de Souza, R.; de
Torres, A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.;
Delgado, H. E.; Di Matteo, P.; Diakite, S.; Diener, C.; Distefano,
E.; Dolding, C.; Drazinos, P.; Durán, J.; Edvardsson, B.; Enke, H.;
Eriksson, K.; Esquej, P.; Eynard Bontemps, G.; Fabre, C.; Fabrizio,
M.; Faigler, S.; Falcão, A. J.; Farràs Casas, M.; Federici, L.;
Fedorets, G.; Fernique, P.; Figueras, F.; Filippi, F.; Findeisen, K.;
Fonti, A.; Fraile, E.; Fraser, M.; Frézouls, B.; Gai, M.; Galleti,
S.; Garabato, D.; García-Sedano, F.; Garofalo, A.; Garralda, N.;
Gavel, A.; Gavras, P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore,
G.; Girona, S.; Giuffrida, G.; Glass, F.; Gomes, M.; Granvik, M.;
Gueguen, A.; Guerrier, A.; Guiraud, J.; Gutiérrez-Sánchez, R.;
Haigron, R.; Hatzidimitriou, D.; Hauser, M.; Haywood, M.; Heiter,
U.; Heu, J.; Hilger, T.; Hofmann, W.; Holland, G.; Huckle, H. E.;
Hypki, A.; Icardi, V.; Janßen, K.; Jevardat de Fombelle, G.; Jonker,
P. G.; Juhász, Á. L.; Julbe, F.; Karampelas, A.; Kewley, A.; Klar,
J.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.; Kontizas,
E.; Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.; Koubsky,
P.; Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; López,
M.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant,
J. M.; Marconi, M.; Marinoni, S.; Marschalkó, G.; Marshall, D. J.;
Martino, M.; Marton, G.; Mary, N.; Matijevič, G.; Mazeh, T.; Messina,
S.; Michalik, D.; Millar, N. R.; Molina, D.; Molinaro, R.; Molnár,
L.; Montegriffo, P.; Mor, R.; Morbidelli, R.; Morel, T.; Morris, D.;
Mulone, A. F.; Muraveva, T.; Musella, I.; Nelemans, G.; Nicastro,
L.; Noval, L.; O'Mullane, W.; Ordénovic, C.; Ordóñez-Blanco,
D.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.; Palacin, H.;
Palaversa, L.; Panahi, A.; Pawlak, M.; Piersimoni, A. M.; Pineau,
F. -X.; Plachy, E.; Plum, G.; Poggio, E.; Poujoulet, E.; Prša, A.;
Pulone, L.; Racero, E.; Ragaini, S.; Rambaux, N.; Ramos-Lerate, M.;
Regibo, S.; Riclet, F.; Ripepi, V.; Riva, A.; Rivard, A.; Rixon, G.;
Roegiers, T.; Roelens, M.; Romero-Gómez, M.; Rowell, N.; Royer,
F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann,
J.; Salgado, J.; Salguero, E.; Sanna, N.; Santana-Ros, T.; Sarasso,
M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.; Segovia,
J. C.; Ségransan, D.; Shih, I. -C.; Siltala, L.; Silva, A. F.; Smart,
R. L.; Smith, K. W.; Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto,
S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.;
Steidelmüller, H.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Surdej,
J.; Szabados, L.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran,
G.; Taylor, M. B.; Teixeira, R.; Terrett, D.; Teyssandier, P.;
Thuillot, W.; Titarenko, A.; Torra Clotet, F.; Turon, C.; Ulla, A.;
Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini, G.; Valette, V.;
van Elteren, A.; Van Hemelryck, E.; van Leeuwen, M.; Vaschetto, M.;
Vecchiato, A.; Viala, Y.; Vicente, D.; Vogt, S.; von Essen, C.; Voss,
H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Wertz, O.;
Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Ziaeepour,
H.; Zorec, J.; Zschocke, S.; Zucker, S.; Zurbach, C.; Zwitter, T.
2020A&A...642C...1G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: VizieR Online Data Catalog: Atomic data for the Gaia-ESO Survey
(Heiter+, 2021)
Authors: Heiter, U.; Lind, K.; Bergemann, M.; Asplund, M.; Mikolaitis,
S.; Barklem, P. S.; Masseron, T.; de Laverny, P.; Magrini, L.;
Edvardsson, B.; Joensson, H.; Pickering, J. C.; Ryde, N.; Bayo Aran,
A.; Bensby, T.; Casey, A. R.; Feltzing, S.; Jofre, P.; Korn, A. J.;
Pancino, E.; Damiani, F.; Lanzafame, A.; Lardo, C.; Monaco, L.;
Morbidelli, L.; Smiljanic, R.; Worley, C.; Zaggia, S.; Randich, S.;
Gilmore, G. F.
2020yCat..36450106H Altcode:
In general experimental transition probabilities were preferred but
theoretical values were also used. Astrophysical gf-values were avoided
due to the model-dependence of such a procedure. Synthetic stellar
spectra calculated for the Sun and Arcturus were used to assess
the blending properties of the lines. We also performed a detailed
investigation of available data for line broadening due to collisions
with neutral hydrogen atoms, which are included in the data table as
"Van der Waals broadening". <P />The atomic data are stored in a single
table with one record for each transition. Hyperfine structure (HFS)
components and different isotopes are included as separate transitions,
where applicable. HFS components belonging to the same fine structure
transition can be identified by having the exact same label and J
value for both the lower and the upper levels. Both the preselected
lines and the background line list are included. Preselected lines can
be identified by having both non-empty (not '-') gf_flag and synflag
entries. The set of molecular data is stored in a separate table. <P
/>We strongly encourage users of the Gaia-ESO line list to cite,
in addition to the overview article, the individual sources for the
atomic and molecular data used in a particular work. It is important
that providers of atomic data receive credit for their work by citing
the original publications. This is also a prerequisite for the continued
funding of this type of research. To facilitate citations of original
sources we provide, together with the data table, a BibTeX file with
the relevant entries. <P />(4 data files).
---------------------------------------------------------
Title: Excitation and charge transfer in low-energy hydrogen atom
collisions with neutral manganese and titanium
Authors: Grumer, J.; Barklem, P. S.
2020A&A...637A..28G Altcode: 2020arXiv200310029G
Data for inelastic processes due to hydrogen atom collisions with
manganese and titanium are needed for accurate modeling of the
corresponding spectra in late-type stars. In this work excitation and
charge transfer in low-energy Mn+H and Ti+H collisions have been studied
theoretically using a method based on an asymptotic two-electron linear
combination of an atomic orbitals model of ionic-covalent interactions
in the neutral atom-hydrogen-atom system, together with the multichannel
Landau-Zener model to treat the dynamics. Extensive calculations
of charge transfer (mutual neutralization, ion-pair production),
excitation and de-excitation processes in the two collisional systems
are carried out for all transitions between covalent states dissociating
to energies below the first ionic limit and the dominating ionic
states. Rate coefficients are determined for temperatures in the
range 1000-20 000 K in steps of 1000 K. Like for earlier studies of
other atomic species, charge transfer processes are found to lead to
much larger rate coefficients than excitation processes. <P />The
complete set of data is made available in electronic form at: <A
href="https://github.com/barklem/public-data">https://github.com/barklem/public-data</A>.
---------------------------------------------------------
Title: Gaia Data Release 2. Kinematics of globular clusters and
dwarf galaxies around the Milky Way (Corrigendum)
Authors: Gaia Collaboration; Helmi, A.; van Leeuwen, F.; McMillan,
P. J.; Massari, D.; Antoja, T.; Robin, A. C.; Lindegren, L.;
Bastian, U.; Arenou, F.; Babusiaux, C.; Biermann, M.; Breddels,
M. A.; Hobbs, D.; Jordi, C.; Pancino, E.; Reylé, C.; Veljanoski,
J.; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne,
J. H. J.; Bailer-Jones, C. A. L.; Evans, D. W.; Eyer, L.; Jansen,
F.; Klioner, S. A.; Lammers, U.; Luri, X.; Mignard, F.; Panem,
C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.;
Soubiran, C.; Walton, N. A.; Cropper, M.; Drimmel, R.; Katz, D.;
Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castañeda, J.; Chaoul,
L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra, R.; Holl, B.;
Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Panuzzo,
P.; Portell, J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thévenin,
F.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Teyssier,
D.; Altmann, M.; Andrae, R.; Audard, M.; Bellas-Velidis, I.; Benson,
K.; Berthier, J.; Blomme, R.; Burgess, P.; Busso, G.; Carry, B.;
Cellino, A.; Clementini, G.; Clotet, M.; Creevey, O.; Davidson,
M.; De Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.;
Fernández-Hernández, J.; Fouesneau, M.; Frémat, Y.; Galluccio, L.;
García-Torres, M.; González-Núñez, J.; González-Vidal, J. J.;
Gosset, E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison,
D. L.; Hernández, J.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.;
Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.;
Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.; Löffler, W.;
Manteiga, M.; Marrese, P. M.; Martín-Fleitas, J. M.; Moitinho, A.;
Mora, A.; Muinonen, K.; Osinde, J.; Pauwels, T.; Petit, J. -M.;
Recio-Blanco, A.; Richards, P. J.; Rimoldini, L.; Sarro, L. M.;
Siopis, C.; Smith, M.; Sozzetti, A.; Süveges, M.; Torra, J.; van
Reeven, W.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts, C.;
Altavilla, G.; Álvarez, M. A.; Alvarez, R.; Alves, J.; Anderson,
R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Arcay, B.;
Astraatmadja, T. L.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.;
Balm, P.; Barache, C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem,
P. S.; Barrado, D.; Barros, M.; Barstow, M. A.; Bartholomé Muñoz,
S.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.; Berihuete, A.;
Bertone, S.; Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.; Boch,
T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bossini, D.; Bouquillon,
S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Bressan, A.; Brouillet,
N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli, B.; Burlacu, A.;
Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau, E.; Cancelliere,
R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo, R.; Carlucci, T.;
Carrasco, J. M.; Casamiquela, L.; Castellani, M.; Castro-Ginard, A.;
Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza, G.; Costigan, G.;
Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypers, J.; Dafonte,
C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; de Laverny,
P.; De Luise, F.; De March, R.; de Martino, D.; de Souza, R.; de
Torres, A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.;
Delgado, H. E.; Di Matteo, P.; Diakite, S.; Diener, C.; Distefano,
E.; Dolding, C.; Drazinos, P.; Durán, J.; Edvardsson, B.; Enke, H.;
Eriksson, K.; Esquej, P.; Eynard Bontemps, G.; Fabre, C.; Fabrizio,
M.; Faigler, S.; Falcão, A. J.; Farràs Casas, M.; Federici, L.;
Fedorets, G.; Fernique, P.; Figueras, F.; Filippi, F.; Findeisen, K.;
Fonti, A.; Fraile, E.; Fraser, M.; Frézouls, B.; Gai, M.; Galleti,
S.; Garabato, D.; García-Sedano, F.; Garofalo, A.; Garralda, N.;
Gavel, A.; Gavras, P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore,
G.; Girona, S.; Giuffrida, G.; Glass, F.; Gomes, M.; Granvik, M.;
Gueguen, A.; Guerrier, A.; Guiraud, J.; Gutiérrez-Sánchez, R.;
Haigron, R.; Hatzidimitriou, D.; Hauser, M.; Haywood, M.; Heiter,
U.; Heu, J.; Hilger, T.; Hofmann, W.; Holland, G.; Huckle, H. E.;
Hypki, A.; Icardi, V.; Janßen, K.; Jevardat de Fombelle, G.; Jonker,
P. G.; Juhász, Á. L.; Julbe, F.; Karampelas, A.; Kewley, A.; Klar,
J.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.; Kontizas,
E.; Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.; Koubsky,
P.; Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; López,
M.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant,
J. M.; Marconi, M.; Marinoni, S.; Marschalkó, G.; Marshall, D. J.;
Martino, M.; Marton, G.; Mary, N.; Matijevič, G.; Mazeh, T.; Messina,
S.; Michalik, D.; Millar, N. R.; Molina, D.; Molinaro, R.; Molnár,
L.; Montegriffo, P.; Mor, R.; Morbidelli, R.; Morel, T.; Morris, D.;
Mulone, A. F.; Muraveva, T.; Musella, I.; Nelemans, G.; Nicastro,
L.; Noval, L.; O'Mullane, W.; Ordénovic, C.; Ordóñez-Blanco,
D.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.; Palacin, H.;
Palaversa, L.; Panahi, A.; Pawlak, M.; Piersimoni, A. M.; Pineau,
F. -X.; Plachy, E.; Plum, G.; Poggio, E.; Poujoulet, E.; Prša, A.;
Pulone, L.; Racero, E.; Ragaini, S.; Rambaux, N.; Ramos-Lerate, M.;
Regibo, S.; Riclet, F.; Ripepi, V.; Riva, A.; Rivard, A.; Rixon, G.;
Roegiers, T.; Roelens, M.; Romero-Gómez, M.; Rowell, N.; Royer,
F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann,
J.; Salgado, J.; Salguero, E.; Sanna, N.; Santana-Ros, T.; Sarasso,
M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.; Segovia,
J. C.; Ségransan, D.; Shih, I. -C.; Siltala, L.; Silva, A. F.; Smart,
R. L.; Smith, K. W.; Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto,
S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.;
Steidelmüller, H.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Surdej,
J.; Szabados, L.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran,
G.; Taylor, M. B.; Teixeira, R.; Terrett, D.; Teyssandier, P.;
Thuillot, W.; Titarenko, A.; Torra Clotet, F.; Turon, C.; Ulla, A.;
Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini, G.; Valette, V.;
van Elteren, A.; Van Hemelryck, E.; van Leeuwen, M.; Vaschetto, M.;
Vecchiato, A.; Viala, Y.; Vicente, D.; Vogt, S.; von Essen, C.; Voss,
H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Wertz, O.;
Wevems, T.; Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Ziaeepour,
H.; Zorec, J.; Zschocke, S.; Zucker, S.; Zurbach, C.; Zwitter, T.
2020A&A...637C...3G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The 3D non-LTE solar nitrogen abundance from atomic lines
Authors: Amarsi, A. M.; Grevesse, N.; Grumer, J.; Asplund, M.; Barklem,
P. S.; Collet, R.
2020A&A...636A.120A Altcode: 2020arXiv200312561A
Nitrogen is an important element in various fields of stellar and
Galactic astronomy, and the solar nitrogen abundance is crucial as a
yardstick for comparing different objects in the cosmos. In order to
obtain a precise and accurate value for this abundance, we carried out
N I line formation calculations in a 3D radiative-hydrodynamic STAGGER
model solar atmosphere in full 3D non-local thermodynamic equilibrium
(non-LTE). We used a model atom that includes physically motivated
descriptions for the inelastic collisions of N I with free electrons and
with neutral hydrogen. We selected five N I lines of high excitation
energy to study in detail, based on their strengths and on their
being relatively free of blends. We found that these lines are slightly
strengthened from non-LTE photon losses and from 3D granulation effects,
resulting in negative abundance corrections of around - 0.01 dex and -
0.04 dex, respectively. Our advocated solar nitrogen abundance is log
ɛ<SUB>N</SUB> = 7.77, with the systematic 1σ uncertainty estimated
to be 0.05 dex. This result is consistent with earlier studies after
correcting for differences in line selections and equivalent widths.
---------------------------------------------------------
Title: State of the Profession Considerations for Laboratory
Astrophysics
Authors: Savin, Daniel Wolf; Babb, James F.; Barklem, Paul; Bellan,
Paul M.; Betancourt-Martinez, Gabriele; Blum, Jürgen; Boersma,
Christiaan; Boryta, Mark D.; Brisset, Julie; Brogan, Crystal; Cami,
Jan; Caselli, Paola; Chutjian, Ara; Corrales, Lia; Crabtree, Kyle;
Dominguez, Gerardo; Federman, Steven R.; Fontes, Christopher J.;
Freedman, Richard; Gavilan-Marin, Lisseth; Gibson, Brad; Golub, Leon;
Gorczyca, Thomas W.; Hahn, Michael; Hartmann, Dieter; Hörst, Sarah M.;
Hudson, Reggie L.; Ji, Hantao; Kreckel, Holger; Kuhn, Jeffrey; Lawler,
James E.; Lee, Timothy J.; Leutenegger, Maurice A.; Mancini, Roberto;
Marler, Joan P.; Mashonkina, Lyudmila I.; McCarthy, Michael C.;
McCoustra, Martin; McGuire, Brett A.; Milam, Stefanie N.; Montgomery,
Mike; Murphy, Nicholas A.; Nave, Gillian; Nelson, Robert M.; Nollett,
Kenneth M.; Norton, Aimee A.; Novotný, Oldřich; Papol, Anthony;
Raymond, John C.; Salama, Farid; Sciamma-O'Brien, Ella M.; Smith,
Randall; Sosolik, Chad; Sousa-Silva, Clara; Spyrou, Artemis; Stancil,
Phillip C.; Sung, Keeyoon; Tennyson, Jonathan; Timmes, Frank; Trimble,
Virginia L.; Venot, Olivia; Wahlgren, Glenn; Wargelin, Bradford J.;
Winget, Don; Wood, Michael P.
2019BAAS...51g...7S Altcode: 2019astro2020U...7S
Astrophysics advances, in part, through laboratory astrophysics studies
of the underlying processes controlling the observed properties of
the Cosmos. These studies encompass both theoretical and experimental
research. Robust support for laboratory astrophysics is critically
needed to maximize the scientific return of astronomical observations.
---------------------------------------------------------
Title: Atomic data for astrophysics: Needs and challenges
Authors: Nave, Gillian; Barklem, Paul; Belmonte, Maria Teresa;
Brickhouse, Nancy; Butler, Paul; Cashman, Frances; Chatzikos, M.;
Cowley, Charles R.; Den Hartog, Elizabeth; Federman, Steven; Ferland,
Gary; Fogle, Michael; Hartman, Henrik; Guzman, Francisco; Heap, Sara;
Kerber, Florian; Kramida, Alexander; Kulkarni, Varsha P.; Lawler,
James E.; Marler, Joan; Nahar, Sultana; Pickering, Juliet; Quinet,
Pascal; Ralchenko, Yuri; Savin, Daniel; Sneden, Chris; Takacs, Endre;
Wahlgren, Glenn; Webb, John; Wiseman, Jennifer; Wood, Mike
2019BAAS...51g...1N Altcode: 2019astro2020U...1N
We describe the impact of atomic spectroscopy on astrophysics and future
requirements for atomic data. These requirements cannot be met with
current levels of funding for laboratory astrophysics. The situation
could be substantially improved with relatively small investment from
the funding agencies.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Non-LTE analysis of K I in
late-type stars (Reggiani+, 2019)
Authors: Reggiani, H.; Amarsi, A. M.; Lind, K.; Barklem, P. S.;
Zatsarinny, O.; Bartschat, K.; Fursa, D. V.; Bray, I.; Spina, L.;
Melendez, J.
2019yCat..36270177R Altcode:
We built a new model atom of potassium in order to test the non-LTE
effects in stellar abundances estimations. We used state-of-the-art
calculations of neutral hydrogen and electronic collisional
cross-sections and photoionization cross-sections. <P />(7 data files).
---------------------------------------------------------
Title: Non-LTE analysis of K I in late-type stars
Authors: Reggiani, Henrique; Amarsi, Anish M.; Lind, Karin; Barklem,
Paul S.; Zatsarinny, Oleg; Bartschat, Klaus; Fursa, Dmitry V.; Bray,
Igor; Spina, Lorenzo; Meléndez, Jorge
2019A&A...627A.177R Altcode: 2019arXiv190608281R
Context. Older models of Galactic chemical evolution (GCE) predict
[K/Fe] ratios as much as 1 dex lower than those inferred from stellar
observations. Abundances of potassium are mainly based on analyses of
the 7698 Å resonance line, and the discrepancy between GCE models and
observations is in part caused by the assumption of local thermodynamic
equilibrium (LTE) in spectroscopic analyses. <BR /> Aims: We study
the statistical equilibrium of K I, focusing on the non-LTE effects
on the 7698 Å line. We aim to determine how non-LTE abundances
of potassium can improve the analysis of its chemical evolution,
and help to constrain the yields of GCE models. <BR /> Methods:
We construct a new model K I atom that employs the most up-to-date
atomic data. In particular, we calculate and present inelastic e+K
collisional excitation cross-sections from the convergent close-coupling
(CCC) and the B-Spline R-matrix (BSR) methods, and H+K collisions
from the two-electron model (LCAO). We constructed a fine, extended
grid of non-LTE abundance corrections based on 1D MARCS models that
span 4000 < T<SUB>eff</SUB>/K < 8000, 0.50 < log g <
5.00, - 5.00 < [Fe/H] < + 0.50, and applied the corrections to
potassium abundances extracted from the literature. <BR /> Results:
In concordance with previous studies, we find severe non-LTE effects
in the 7698 Å line. The line is stronger in non-LTE and the abundance
corrections can reach approximately - 0.7 dex for solar-metallicity
stars such as Procyon. We determine potassium abundances in six
benchmark stars, and obtain consistent results from different
optical lines. We explore the effects of atmospheric inhomogeneity by
computing for the first time a full 3D non-LTE stellar spectrum of
K I lines for a test star. We find that 3D modeling is necessary to
predict a correct shape of the resonance 7698 Å line, but the line
strength is similar to that found in 1D non-LTE. <BR /> Conclusions:
Our non-LTE abundance corrections reduce the scatter and change the
cosmic trends of literature potassium abundances. In the regime
[Fe/H] ≲-1.0 the non-LTE abundances show a good agreement with
the GCE model with yields from rotating massive stars. The reduced
scatter of the non-LTE corrected abundances of a sample of solar twins
shows that line-by-line differential analysis techniques cannot fully
compensate for systematic LTE modelling errors; the scatter introduced
by such errors introduces a spurious dispersion to K evolution. <P
/>Data are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/627/A177">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/627/A177</A>
---------------------------------------------------------
Title: Excitation and charge transfer in low-energy hydrogen atom
collisions with neutral carbon and nitrogen
Authors: Amarsi, A. M.; Barklem, P. S.
2019A&A...625A..78A Altcode: 2019arXiv190400210A
Low-energy inelastic collisions with neutral hydrogen atoms are
important processes in stellar atmospheres, and a persistent source of
uncertainty in non-LTE modelling of stellar spectra. We have calculated
and studied excitation and charge transfer of C I and of N I due to
such collisions. We used a previously presented method that is based
on an asymptotic two-electron linear combination of atomic orbitals
(LCAO) model of ionic-covalent interactions for the adiabatic potential
energies, combined with the multichannel Landau-Zener model for the
collision dynamics. We find that charge transfer processes typically
lead to much larger rate coefficients than excitation processes
do, consistent with studies of other atomic species. Two-electron
processes were considered and lead to non-zero rate coefficients that
can potentially impact statistical equilibrium calculations. However,
they were included in the model in an approximate way, via an estimate
for the two-electron coupling that was presented earlier in the
literature: the validity of these data should be checked in a future
work. <P />Atomic data are available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A78">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A78</A>
and at <A
href="https://github.com/barklem/public-data">https://github.com/barklem/public-data</A>
---------------------------------------------------------
Title: 3D non-LTE line formation of neutral carbon in the Sun
Authors: Amarsi, A. M.; Barklem, P. S.; Collet, R.; Grevesse, N.;
Asplund, M.
2019A&A...624A.111A Altcode: 2019arXiv190308838A
Carbon abundances in late-type stars are important in a variety of
astrophysical contexts. However C I lines, one of the main abundance
diagnostics, are sensitive to departures from local thermodynamic
equilibrium (LTE). We present a model atom for non-LTE analyses of C
I lines, that uses a new, physically-motivated recipe for the rates
of neutral hydrogen impact excitation. We analyse C I lines in the
solar spectrum, employing a three-dimensional (3D) hydrodynamic
model solar atmosphere and 3D non-LTE radiative transfer. We find
negative non-LTE abundance corrections for C I lines in the solar
photosphere, in accordance with previous studies, reaching up to
around 0.1 dex in the disk-integrated flux. We also present the first
fully consistent 3D non-LTE solar carbon abundance determination:
we infer log ɛ<SUB>C</SUB> = 8.44 ± 0.02, in good agreement with
the current standard value. Our models reproduce the observed solar
centre-to-limb variations of various C I lines, without any adjustments
to the rates of neutral hydrogen impact excitation, suggesting that
the proposed recipe may be a solution to the long-standing problem of
how to reliably model inelastic collisions with neutral hydrogen in
late-type stellar atmospheres.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Carbon and nitrogen rate
coefficients (Amarsi+, 2019)
Authors: Amarsi, A. M.; Barklem, P. S.
2019yCat..36250078A Altcode:
c-state.dat contains information about the carbon states n-state.dat
contains information about the nitrogen states c-rate.dat contains the
rate coefficients for carbon n-rate.dat contains the rate coefficients
for nitrogen <P />(4 data files).
---------------------------------------------------------
Title: 4MOST: Project overview and information for the First Call
for Proposals
Authors: de Jong, R. S.; Agertz, O.; Berbel, A. A.; Aird, J.;
Alexander, D. A.; Amarsi, A.; Anders, F.; Andrae, R.; Ansarinejad,
B.; Ansorge, W.; Antilogus, P.; Anwand-Heerwart, H.; Arentsen, A.;
Arnadottir, A.; Asplund, M.; Auger, M.; Azais, N.; Baade, D.; Baker,
G.; Baker, S.; Balbinot, E.; Baldry, I. K.; Banerji, M.; Barden,
S.; Barklem, P.; Barthélémy-Mazot, E.; Battistini, C.; Bauer, S.;
Bell, C. P. M.; Bellido-Tirado, O.; Bellstedt, S.; Belokurov, V.;
Bensby, T.; Bergemann, M.; Bestenlehner, J. M.; Bielby, R.; Bilicki,
M.; Blake, C.; Bland-Hawthorn, J.; Boeche, C.; Boland, W.; Boller,
T.; Bongard, S.; Bongiorno, A.; Bonifacio, P.; Boudon, D.; Brooks,
D.; Brown, M. J. I.; Brown, R.; Brüggen, M.; Brynnel, J.; Brzeski,
J.; Buchert, T.; Buschkamp, P.; Caffau, E.; Caillier, P.; Carrick,
J.; Casagrande, L.; Case, S.; Casey, A.; Cesarini, I.; Cescutti, G.;
Chapuis, D.; Chiappini, C.; Childress, M.; Christlieb, N.; Church, R.;
Cioni, M. -R. L.; Cluver, M.; Colless, M.; Collett, T.; Comparat, J.;
Cooper, A.; Couch, W.; Courbin, F.; Croom, S.; Croton, D.; Daguisé,
E.; Dalton, G.; Davies, L. J. M.; Davis, T.; de Laverny, P.; Deason,
A.; Dionies, F.; Disseau, K.; Doel, P.; Döscher, D.; Driver, S. P.;
Dwelly, T.; Eckert, D.; Edge, A.; Edvardsson, B.; Youssoufi, D. E.;
Elhaddad, A.; Enke, H.; Erfanianfar, G.; Farrell, T.; Fechner, T.;
Feiz, C.; Feltzing, S.; Ferreras, I.; Feuerstein, D.; Feuillet, D.;
Finoguenov, A.; Ford, D.; Fotopoulou, S.; Fouesneau, M.; Frenk, C.;
Frey, S.; Gaessler, W.; Geier, S.; Gentile Fusillo, N.; Gerhard,
O.; Giannantonio, T.; Giannone, D.; Gibson, B.; Gillingham, P.;
González-Fernández, C.; Gonzalez-Solares, E.; Gottloeber, S.; Gould,
A.; Grebel, E. K.; Gueguen, A.; Guiglion, G.; Haehnelt, M.; Hahn, T.;
Hansen, C. J.; Hartman, H.; Hauptner, K.; Hawkins, K.; Haynes, D.;
Haynes, R.; Heiter, U.; Helmi, A.; Aguayo, C. H.; Hewett, P.; Hinton,
S.; Hobbs, D.; Hoenig, S.; Hofman, D.; Hook, I.; Hopgood, J.; Hopkins,
A.; Hourihane, A.; Howes, L.; Howlett, C.; Huet, T.; Irwin, M.; Iwert,
O.; Jablonka, P.; Jahn, T.; Jahnke, K.; Jarno, A.; Jin, S.; Jofre,
P.; Johl, D.; Jones, D.; Jönsson, H.; Jordan, C.; Karovicova, I.;
Khalatyan, A.; Kelz, A.; Kennicutt, R.; King, D.; Kitaura, F.; Klar,
J.; Klauser, U.; Kneib, J. -P.; Koch, A.; Koposov, S.; Kordopatis, G.;
Korn, A.; Kosmalski, J.; Kotak, R.; Kovalev, M.; Kreckel, K.; Kripak,
Y.; Krumpe, M.; Kuijken, K.; Kunder, A.; Kushniruk, I.; Lam, M. I.;
Lamer, G.; Laurent, F.; Lawrence, J.; Lehmitz, M.; Lemasle, B.; Lewis,
J.; Li, B.; Lidman, C.; Lind, K.; Liske, J.; Lizon, J. -L.; Loveday,
J.; Ludwig, H. -G.; McDermid, R. M.; Maguire, K.; Mainieri, V.; Mali,
S.; Mandel, H.; Mandel, K.; Mannering, L.; Martell, S.; Martinez
Delgado, D.; Matijevic, G.; McGregor, H.; McMahon, R.; McMillan,
P.; Mena, O.; Merloni, A.; Meyer, M. J.; Michel, C.; Micheva, G.;
Migniau, J. -E.; Minchev, I.; Monari, G.; Muller, R.; Murphy, D.;
Muthukrishna, D.; Nandra, K.; Navarro, R.; Ness, M.; Nichani, V.;
Nichol, R.; Nicklas, H.; Niederhofer, F.; Norberg, P.; Obreschkow, D.;
Oliver, S.; Owers, M.; Pai, N.; Pankratow, S.; Parkinson, D.; Paschke,
J.; Paterson, R.; Pecontal, A.; Parry, I.; Phillips, D.; Pillepich,
A.; Pinard, L.; Pirard, J.; Piskunov, N.; Plank, V.; Plüschke, D.;
Pons, E.; Popesso, P.; Power, C.; Pragt, J.; Pramskiy, A.; Pryer,
D.; Quattri, M.; Queiroz, A. B. d. A.; Quirrenbach, A.; Rahurkar,
S.; Raichoor, A.; Ramstedt, S.; Rau, A.; Recio-Blanco, A.; Reiss, R.;
Renaud, F.; Revaz, Y.; Rhode, P.; Richard, J.; Richter, A. D.; Rix,
H. -W.; Robotham, A. S. G.; Roelfsema, R.; Romaniello, M.; Rosario, D.;
Rothmaier, F.; Roukema, B.; Ruchti, G.; Rupprecht, G.; Rybizki, J.;
Ryde, N.; Saar, A.; Sadler, E.; Sahlén, M.; Salvato, M.; Sassolas,
B.; Saunders, W.; Saviauk, A.; Sbordone, L.; Schmidt, T.; Schnurr,
O.; Scholz, R. -D.; Schwope, A.; Seifert, W.; Shanks, T.; Sheinis,
A.; Sivov, T.; Skúladóttir, Á.; Smartt, S.; Smedley, S.; Smith,
G.; Smith, R.; Sorce, J.; Spitler, L.; Starkenburg, E.; Steinmetz,
M.; Stilz, I.; Storm, J.; Sullivan, M.; Sutherland, W.; Swann, E.;
Tamone, A.; Taylor, E. N.; Teillon, J.; Tempel, E.; ter Horst, R.;
Thi, W. -F.; Tolstoy, E.; Trager, S.; Traven, G.; Tremblay, P. -E.;
Tresse, L.; Valentini, M.; van de Weygaert, R.; van den Ancker, M.;
Veljanoski, J.; Venkatesan, S.; Wagner, L.; Wagner, K.; Walcher,
C. J.; Waller, L.; Walton, N.; Wang, L.; Winkler, R.; Wisotzki, L.;
Worley, C. C.; Worseck, G.; Xiang, M.; Xu, W.; Yong, D.; Zhao, C.;
Zheng, J.; Zscheyge, F.; Zucker, D.
2019Msngr.175....3D Altcode: 2019arXiv190302464D
We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST),
a new high-multiplex, wide-field spectroscopic survey facility under
development for the four-metre-class Visible and Infrared Survey
Telescope for Astronomy (VISTA) at Paranal. Its key specifications
are: a large field of view (FoV) of 4.2 square degrees and a high
multiplex capability, with 1624 fibres feeding two low-resolution
spectrographs (R = λ/Δλ 6500), and 812 fibres transferring light
to the high-resolution spectrograph (R 20 000). After a description of
the instrument and its expected performance, a short overview is given
of its operational scheme and planned 4MOST Consortium science; these
aspects are covered in more detail in other articles in this edition
of The Messenger. Finally, the processes, schedules, and policies
concerning the selection of ESO Community Surveys are presented,
commencing with a singular opportunity to submit Letters of Intent
for Public Surveys during the first five years of 4MOST operations.
---------------------------------------------------------
Title: Ca line formation in late-type stellar atmospheres. I. The
model atom
Authors: Osorio, Y.; Lind, K.; Barklem, P. S.; Allende Prieto, C.;
Zatsarinny, O.
2019A&A...623A.103O Altcode: 2019arXiv190111442O
Context. Departures from local thermodynamic equilibrium (LTE) distort
the calcium abundance derived from stellar spectra in various ways,
depending on the lines used and the stellar atmospheric parameters. The
collection of atomic data adopted in non-LTE (NLTE) calculations
must be sufficiently complete and accurate. <BR /> Aims: We derive
NLTE abundances from high-quality observations and reliable stellar
parameters using a model atom built afresh for this work, and check the
consistency of our results over a wide wavelength range with transitions
of atomic and singly ionised calcium. <BR /> Methods: We built and
tested Ca I and Ca II model atoms with state-of-the-art radiative
and collisional data, and tested their performance deriving the Ca
abundance in three benchmark stars: Procyon, the Sun, and Arcturus. We
have excellent-quality observations and accurate stellar parameters for
these stars. Two methods to derive the LTE/NLTE abundances were used
and compared. The LTE/NLTE centre-to-limb variation (CLV) of Ca lines
in the Sun was also investigated. <BR /> Results: The two methods used
give similar results in all three stars. Several discrepancies found
in LTE do not appear in our NLTE results; in particular the agreement
between abundances in the visual and infra-red (IR) and the Ca I and
Ca II ionisation balance is improved overall, although substantial
line-to-line scatter remains. The CLV of the calcium lines around 6165
Å can be partially reproduced. We suspect differences between our
modelling and CLV results are due to inhomogeneities in the atmosphere
that require 3D modelling.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Gaia DR2. Variable stars in CMD
(Gaia Collaboration+, 2019)
Authors: Gaia Collaboration; Eyer, L.; Rimoldini, L.; Audard, M.;
Anderson, R. I.; Nienartowicz, K.; Glass, F.; Marchal, O.; Grenon, M.;
Mowlavi, N.; Holl, B.; Clementini, G.; Aerts, C.; Mazeh, T.; Evans,
D. W.; Szabados, L.; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de
Bruijne, J. H. J.; Babusiaux, C.; Bailer-Jones, C. A. L.; Biermann,
M.; Jansen, F.; Jordi, C.; Klioner, S. A.; Lammers, U.; Lindegren,
L.; Luri, X.; Mignard, F.; Panem, C.; Pourbaix, D.; Randich, S.;
Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; van Leeuwen, F.;
Walton, N. A.; Arenou, F.; Bastian, U.; Cropper, M.; Drimmel, R.;
Katz, D.; Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castaneda,
J.; Chaoul, L.; Cheek, N.; de Angeli, F.; Fabricius, C.; Guerra,
R.; Masana, E.; Messineo, R.; Panuzzo, P.; Portell, J.; Riello, M.;
Seabroke, G. M.; Tanga, P.; Thevenin, F.; Gracia-Abril, G.; Comoretto,
G.; Garcia-Reinaldos, M.; Teyssier, D.; Altmann, M.; Andrae, R.;
Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme, R.; Burgess,
P.; Busso, G.; Carry, B.; Cellino, A.; Clotet, M.; Creevey, O.;
Davidson, M.; de Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant,
C.; Fernandez-Hernandez, J.; Fouesneau, M.; Fremat, Y.; Galluccio, L.;
Garcia-Torres, M.; Gonzalez-Nunez, J.; Gonzalez-Vidal, J. J.; Gosset,
E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison, D. L.;
Hernandez, J.; Hestroer, D.; Hodgkin, S. T.; Hutton, A.; Jasniewicz,
G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.; Krone-Martins,
A.; Lanzafame, A. C.; Lebzelter, T.; Loeer, W.; Manteiga, M.; Marrese,
P. M.; Martin-Fleitas, J. M.; Moitinho, A.; Mora, A.; Muinonen, K.;
Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J. -M.; Recio-Blanco,
A.; Richards, P. J.; Robin, A. C.; Sarro, L. M.; Siopis, C.; Smith,
M.; Sozzetti, A.; Sueveges, M.; Torra, J.; van Reeven, W.; Abbas,
U.; Abreu Aramburu, A.; Accart, S.; Altavilla, G.; Alvarez, M. A.;
Alvarez, R.; Alves, J.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.;
Antoja, T.; Arcay, B.; Astraatmadja, T. L.; Bach, N.; Baker, S. G.;
Balaguer-Nunez, L.; Balm, P.; Barache, C.; Barata, C.; Barbato, D.;
Barblan, F.; Barklem, P. S.; Barrado, D.; Barros, M.; Barstow, M. A.;
Bartholome Munoz, S.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.;
Berihuete, A.; Bertone, S.; Bianchi, L.; Bienayme, O.; Blanco-Cuaresma,
S.; Boch, T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bossini, D.;
Bouquillon, S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Breddels,
M. A.; Bressan, A.; Brouillet, N.; Bruesemeister, T.; Brugaletta,
E.; Bucciarelli, B.; Burlacu, A.; Busonero, D.; Butkevich, A. G.;
Buzzi, R.; Caau, E.; Cancelliere, R.; Cannizzaro, G.; Cantat-Gaudin,
T.; Carballo, R.; Carlucci, T.; Carrasco, J. M.; Casamiquela, L.;
Castellani, M.; Castro-Ginard, A.; Charlot, P.; Chemin, L.; Chiavassa,
A.; Cocozza, G.; Costigan, G.; Cowell, S.; Crifo, F.; Crosta, M.;
Crowley, C.; Cuypersy, J.; Dafonte, C.; Damerdji, Y.; Dapergolas,
A.; David, P.; David, M.; de Laverny, P.; de Luise, F.; de March,
R.; de Martino, D.; de Souza, R.; de Torres, A.; Debosscher, J.;
Del Pozo, E.; Delbo, M.; Delgado, A.; Delgado, H. E.; Diakite, S.;
Diener, C.; Distefano, E.; Dolding, C.; Drazinos, P.; Duran, J.;
Edvardsson, B.; Enke, H.; Eriksson, K.; Esquej, P.; Eynard Bontemps,
G.; Fabre, C.; Fabrizio, M.; Faigler, S.; Falcao, A. J.; Farras Casas,
M.; Federici, L.; Fedorets, G.; Fernique, P.; Figueras, F.; Filippi,
F.; Findeisen, K.; Fonti, A.; Fraile, E.; Fraser, M.; Frezouls, B.;
Gai, M.; Galleti, S.; Garabato, D.; Garcia-Sedano, F.; Garofalo, A.;
Garralda, N.; Gavel, A.; Gavras, P.; Gerssen, J.; Geyer, R.; Giacobbe,
P.; Gilmore, G.; Girona, S.; Giurida, G.; Gomes, M.; Granvik, M.;
Gueguen, A.; Guerrier, A.; Guiraud, J.; Gutierrez-Sanchez, R.; Haigron,
R.; Hatzidimitriou, D.; Hauser, M.; Haywood, M.; Heiter, U.; Helmi,
A.; Heu, J.; Hilger, T.; Hobbs, D.; Hofmann, W.; Holland, G.; Huckle,
H. E.; Hypki, A.; Icardi, V.; Janssen, K.; Jevardat de Fombelle,
G.; Jonker, P. G.; Juhasz, A. L.; Julbe, F.; Karampelas, A.; Kewley,
A.; Klar, J.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.;
Kontizas, E.; Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.;
Koubsky, P.; Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.;
Le Fustec, Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.;
Leclerc, N.; Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.;
Licata, E.; Lindstrom, H. E. P.; Lister, T. A.; Livanou, E.; Lobel,
A.; Lopez, M.; Lorenz, D.; Managau, S.; Mann, R. G.; Mantelet, G.;
Marchant, J. M.; Marconi, M.; Marinoni, S.; Marschalko, G.; Marshall,
D. J.; Martino, M.; Marton, G.; Mary, N.; Massari, D.; Matijevic, G.;
McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Molina,
D.; Molinaro, R.; Molnar, L.; Montegrio, P.; Mor, R.; Morbidelli, R.;
Morel, T.; Morgenthaler, S.; Morris, D.; Mulone, A. F.; Muraveva, T.;
Musella, I.; Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane, W.;
Ordenovic, C.; Ordonez-Blanco, D.; Osborne, P.; Pagani, C.; Pagano,
I.; Pailler, F.; Palacin, H.; Palaversa, L.; Panahi, A.; Pawlak, M.;
Piersimoni, A. M.; Pineau, F. -X.; Plachy, E.; Plum, G.; Poggio,
E.; Poujoulet, E.; Prsa, A.; Pulone, L.; Racero, E.; Ragaini, S.;
Rambaux, N.; Ramos-Lerate, M.; Regibo, S.; Reyle, C.; Riclet, F.;
Ripepi, V.; Riva, A.; Rivard, A.; Rixon, G.; Roegiers, T.; Roelens,
M.; Romero-Gomez, M.; Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski,
G.; Sagrista Selles, T.; Sahlmann, J.; Salgado, J.; Salguero, E.;
Sanna, N.; Santana-Ros, T.; Sarasso, M.; Savietto, H.; Schultheis, M.;
Sciacca, E.; Segol, M.; Segovia, J. C.; Segransan, D.; Shih, I. -C.;
Siltala, L.; Silva, A. F.; Smart, R. L.; Smith, K. W.; Solano, E.;
Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.; Spagna, A.;
Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmueller, H.; Stephenson,
C. A.; Stoev, H.; Suess, F. F.; Surdej, J.; Szegedi-Elek, E.; Tapiador,
D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett, D.;
Teyssandier, P.; Thuillot, W.; Titarenko, A.; Torra Clotet, F.; Turon,
C.; Ulla, A.; Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini, G.;
Valette, V.; van Elteren, A.; van Hemelryck, E.; van Leeuwen, M.;
Vaschetto, M.; Vecchiato, A.; Veljanoski, J.; Viala, Y.; Vicente,
D.; Vogt, S.; von Essen, C.; Voss, H.; Votruba, V.; Voutsinas, S.;
Walmsley, G.; Weiler, M.; Wertz, O.; Wevers, T.; Wyrzykowski, L.;
Yoldas, A.; Zerjal, M.; Ziaeepour, H.; Zorec, J.; Zschocke, S.;
Zucker, S.; Zurbach, C.; Zwitter, T.
2019yCat..36230110G Altcode:
Time series in the G, BP, and RP bands of the selected field-of-view
transits for 224 sources that are not published in Gaia DR2, but
are plotted in Fig. 11. An animated version of Fig. 11 is provided
online and at https://www.cosmos.esa.int/web/gaia/gaiadr2_cu7. <P />(2
data files).
---------------------------------------------------------
Title: 4MOST Consortium Survey 2: The Milky Way Halo High-Resolution
Survey
Authors: Christlieb, N.; Battistini, C.; Bonifacio, P.; Caffau, E.;
Ludwig, H. -G.; Asplund, M.; Barklem, P.; Bergemann, M.; Church, R.;
Feltzing, S.; Ford, D.; Grebel, E. K.; Hansen, C. J.; Helmi, A.;
Kordopatis, G.; Kovalev, M.; Korn, A.; Lind, K.; Quirrenbach, A.;
Rybizki, J.; Skúladóttir, Á.; Starkenburg, E.
2019Msngr.175...26C Altcode: 2019arXiv190302468C
We will study the formation history of the Milky Way, and the earliest
phases of its chemical enrichment, with a sample of more than 1.5
million stars at high galactic latitude. Elemental abundances of up to
20 elements with a precision of better than 0.2 dex will be derived
for these stars. The sample will include members of kinematically
coherent substructures, which we will associate with their possible
birthplaces by means of their abundance signatures and kinematics,
allowing us to test models of galaxy formation. Our target catalogue
is also expected to contain 30 000 stars at a metallicity of less than
one hundredth that of the Sun. This sample will therefore be almost
a factor of 100 larger than currently existing samples of metal-poor
stars for which precise elemental abundances are available (determined
from high-resolution spectroscopy), enabling us to study the early
chemical evolution of the Milky Way in unprecedented detail.
---------------------------------------------------------
Title: Gaia Data Release 2. Variable stars in the colour-absolute
magnitude diagram
Authors: Gaia Collaboration; Eyer, L.; Rimoldini, L.; Audard, M.;
Anderson, R. I.; Nienartowicz, K.; Glass, F.; Marchal, O.; Grenon,
M.; Mowlavi, N.; Holl, B.; Clementini, G.; Aerts, C.; Mazeh, T.;
Evans, D. W.; Szabados, L.; Brown, A. G. A.; Vallenari, A.; Prusti,
T.; de Bruijne, J. H. J.; Babusiaux, C.; Bailer-Jones, C. A. L.;
Biermann, M.; Jansen, F.; Jordi, C.; Klioner, S. A.; Lammers, U.;
Lindegren, L.; Luri, X.; Mignard, F.; Panem, C.; Pourbaix, D.; Randich,
S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; van Leeuwen, F.;
Walton, N. A.; Arenou, F.; Bastian, U.; Cropper, M.; Drimmel, R.;
Katz, D.; Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castañeda,
J.; Chaoul, L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra,
R.; Masana, E.; Messineo, R.; Panuzzo, P.; Portell, J.; Riello, M.;
Seabroke, G. M.; Tanga, P.; Thévenin, F.; Gracia-Abril, G.; Comoretto,
G.; Garcia-Reinaldos, M.; Teyssier, D.; Altmann, M.; Andrae, R.;
Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme, R.; Burgess,
P.; Busso, G.; Carry, B.; Cellino, A.; Clotet, M.; Creevey, O.;
Davidson, M.; De Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant,
C.; Fernández-Hernández, J.; Fouesneau, M.; Frémat, Y.; Galluccio,
L.; García-Torres, M.; González-Núñez, J.; González-Vidal, J. J.;
Gosset, E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison,
D. L.; Hernández, J.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.;
Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.;
Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.; Löffler, W.;
Manteiga, M.; Marrese, P. M.; Martín-Fleitas, J. M.; Moitinho, A.;
Mora, A.; Muinonen, K.; Osinde, J.; Pancino, E.; Pauwels, T.; Petit,
J. -M.; Recio-Blanco, A.; Richards, P. J.; Robin, A. C.; Sarro,
L. M.; Siopis, C.; Smith, M.; Sozzetti, A.; Süveges, M.; Torra, J.;
van Reeven, W.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Altavilla,
G.; Álvarez, M. A.; Alvarez, R.; Alves, J.; Andrei, A. H.; Anglada
Varela, E.; Antiche, E.; Antoja, T.; Arcay, B.; Astraatmadja, T. L.;
Bach, N.; Baker, S. G.; Balaguer-Núñez, L.; Balm, P.; Barache,
C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem, P. S.; Barrado,
D.; Barros, M.; Barstow, M. A.; Bartholomé Muñoz, S.; Bassilana,
J. -L.; Becciani, U.; Bellazzini, M.; Berihuete, A.; Bertone, S.;
Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.; Boch, T.; Boeche, C.;
Bombrun, A.; Borrachero, R.; Bossini, D.; Bouquillon, S.; Bourda, G.;
Bragaglia, A.; Bramante, L.; Breddels, M. A.; Bressan, A.; Brouillet,
N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli, B.; Burlacu, A.;
Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau, E.; Cancelliere,
R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo, R.; Carlucci, T.;
Carrasco, J. M.; Casamiquela, L.; Castellani, M.; Castro-Ginard, A.;
Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza, G.; Costigan, G.;
Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypers, J.; Dafonte,
C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; de Laverny, P.;
De Luise, F.; De March, R.; de Martino, D.; de Souza, R.; de Torres,
A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.; Delgado,
H. E.; Diakite, S.; Diener, C.; Distefano, E.; Dolding, C.; Drazinos,
P.; Durán, J.; Edvardsson, B.; Enke, H.; Eriksson, K.; Esquej, P.;
Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Faigler, S.; Falcão,
A. J.; Farràs Casas, M.; Federici, L.; Fedorets, G.; Fernique,
P.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.; Fraile,
E.; Fraser, M.; Frézouls, B.; Gai, M.; Galleti, S.; Garabato, D.;
García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel, A.; Gavras,
P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore, G.; Girona, S.;
Giuffrida, G.; Gomes, M.; Granvik, M.; Gueguen, A.; Guerrier, A.;
Guiraud, J.; Gutiérrez-Sánchez, R.; Haigron, R.; Hatzidimitriou,
D.; Hauser, M.; Haywood, M.; Heiter, U.; Helmi, A.; Heu, J.; Hilger,
T.; Hobbs, D.; Hofmann, W.; Holland, G.; Huckle, H. E.; Hypki, A.;
Icardi, V.; Janßen, K.; Jevardat de Fombelle, G.; Jonker, P. G.;
Juhász, Á. L.; Julbe, F.; Karampelas, A.; Kewley, A.; Klar, J.;
Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.; Kontizas, E.;
Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.; Koubsky, P.;
Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; López,
M.; Lorenz, D.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchant,
J. M.; Marconi, M.; Marinoni, S.; Marschalkó, G.; Marshall, D. J.;
Martino, M.; Marton, G.; Mary, N.; Massari, D.; Matijevič, G.;
McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Molina,
D.; Molinaro, R.; Molnár, L.; Montegriffo, P.; Mor, R.; Morbidelli,
R.; Morel, T.; Morgenthaler, S.; Morris, D.; Mulone, A. F.; Muraveva,
T.; Musella, I.; Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane,
W.; Ordénovic, C.; Ordóñez-Blanco, D.; Osborne, P.; Pagani, C.;
Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.; Panahi, A.;
Pawlak, M.; Piersimoni, A. M.; Pineau, F. -X.; Plachy, E.; Plum,
G.; Poggio, E.; Poujoulet, E.; Prša, A.; Pulone, L.; Racero, E.;
Ragaini, S.; Rambaux, N.; Ramos-Lerate, M.; Regibo, S.; Reylé, C.;
Riclet, F.; Ripepi, V.; Riva, A.; Rivard, A.; Rixon, G.; Roegiers,
T.; Roelens, M.; Romero-Gómez, M.; Rowell, N.; Royer, F.; Ruiz-Dern,
L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann, J.; Salgado, J.;
Salguero, E.; Sanna, N.; Santana-Ros, T.; Sarasso, M.; Savietto, H.;
Schultheis, M.; Sciacca, E.; Segol, M.; Segovia, J. C.; Ségransan, D.;
Shih, I. -C.; Siltala, L.; Silva, A. F.; Smart, R. L.; Smith, K. W.;
Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.;
Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmüller, H.;
Stephenson, C. A.; Stoev, H.; Suess, F. F.; Surdej, J.; Szegedi-Elek,
E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira,
R.; Terrett, D.; Teyssandier, P.; Thuillot, W.; Titarenko, A.; Torra
Clotet, F.; Turon, C.; Ulla, A.; Utrilla, E.; Uzzi, S.; Vaillant,
M.; Valentini, G.; Valette, V.; van Elteren, A.; Van Hemelryck,
E.; van Leeuwen, M.; Vaschetto, M.; Vecchiato, A.; Veljanoski, J.;
Viala, Y.; Vicente, D.; Vogt, S.; von Essen, C.; Voss, H.; Votruba,
V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Wertz, O.; Wevers, T.;
Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Ziaeepour, H.; Zorec, J.;
Zschocke, S.; Zucker, S.; Zurbach, C.; Zwitter, T.
2019A&A...623A.110G Altcode: 2018arXiv180409382G
Context. The ESA Gaia mission provides a unique time-domain survey
for more than 1.6 billion sources with G ≲ 21 mag. <BR /> Aims:
We showcase stellar variability in the Galactic colour-absolute
magnitude diagram (CaMD). We focus on pulsating, eruptive, and
cataclysmic variables, as well as on stars that exhibit variability
that is due to rotation and eclipses. <BR /> Methods: We describe
the locations of variable star classes, variable object fractions,
and typical variability amplitudes throughout the CaMD and show
how variability-related changes in colour and brightness induce
"motions". To do this, we use 22 months of calibrated photometric,
spectro-photometric, and astrometric Gaia data of stars with a
significant parallax. To ensure that a large variety of variable
star classes populate the CaMD, we crossmatched Gaia sources with
known variable stars. We also used the statistics and variability
detection modules of the Gaia variability pipeline. Corrections for
interstellar extinction are not implemented in this article. <BR />
Results: Gaia enables the first investigation of Galactic variable
star populations in the CaMD on a similar, if not larger, scale as
was previously done in the Magellanic Clouds. Although the observed
colours are not corrected for reddening, distinct regions are visible
in which variable stars occur. We determine variable star fractions
to within the current detection thresholds of Gaia. Finally,
we report the most complete description of variability-induced
motion within the CaMD to date. <BR /> Conclusions: Gaia enables
novel insights into variability phenomena for an unprecedented
number of stars, which will benefit the understanding of stellar
astrophysics. The CaMD of Galactic variable stars provides crucial
information on physical origins of variability in a way that
has previously only been accessible for Galactic star clusters or
external galaxies. Future Gaia data releases will enable significant
improvements over this preview by providing longer time series, more
accurate astrometry, and additional data types (time series BP and
RP spectra, RVS spectra, and radial velocities), all for much larger
samples of stars. <P />A movie associated to Fig. 11 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/201833304/olm">https://www.aanda.org</A>.Data
are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A110">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A110</A>.
---------------------------------------------------------
Title: 4MOST Consortium Survey 4: Milky Way Disc and Bulge
High-Resolution Survey (4MIDABLE-HR)
Authors: Bensby, T.; Bergemann, M.; Rybizki, J.; Lemasle, B.; Howes,
L.; Kovalev, M.; Agertz, O.; Asplund, M.; Barklem, P.; Battistini,
C.; Casagrande, L.; Chiappini, C.; Church, R.; Feltzing, S.; Ford,
D.; Gerhard, O.; Kushniruk, I.; Kordopatis, G.; Lind, K.; Minchev,
I.; McMillan, P.; Rix, H. -W.; Ryde, N.; Traven, G.
2019Msngr.175...35B Altcode: 2019arXiv190302470B
The signatures of the formation and evolution of a galaxy are
imprinted in its stars. Their velocities, ages, and chemical
compositions present major constraints on models of galaxy formation,
and on various processes such as the gas inflows and outflows,
the accretion of cold gas, radial migration, and the variability of
star formation activity. Understanding the evolution of the Milky
Way requires large observational datasets of stars via which these
quantities can be determined accurately. This is the science driver
of the 4MOST MIlky way Disc And BuLgE High-Resolution (4MIDABLE-HR)
survey: to obtain high-resolution spectra at < i>R 20 000 and
to provide detailed elemental abundances for large samples of stars
in the Galactic disc and bulge. High data quality will allow us to
provide accurate spectroscopic diagnostics of two million stellar
spectra: precise radial velocities; rotation; abundances of many
elements, including those that are currently only accessible in the
optical, such as Li, s-, and r-process; and multi-epoch spectra for a
sub-sample of stars. Synergies with complementary missions like Gaia
and TESS will provide masses, stellar ages and multiplicity, forming a
multi-dimensional dataset that will allow us to explore and constrain
the origin and structure of the Milky Way.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Abundances in 6 metal-poor stars
(Roederer+, 2018)
Authors: Roederer, I. U.; Barklem, P. S.
2019yCat..18570002R Altcode:
We download UV spectra from the Mikulski Archive for Space Telescopes
(MAST). These spectra were collected using the Space Telescope
Imaging Spectrograph (STIS) on board the Hubble Space Telescope
(HST). We consider a star for inclusion in the sample if extant
R~30000 or R~114000 spectra cover at least 2037<=λ<=2127Å,
where the CuII and ZnII lines are found. We supplement the UV
spectra with high-resolution optical spectra downloaded from online
archives, including the European Southern Observatory (ESO) Science
Archive Facility and the Keck Observatory Archives. These data were
collected with the Ultraviolet and Visual Echelle Spectrograph (UVES)
on the Very Large Telescope, the High Accuracy Radial velocity Planet
Searcher (HARPS) on the ESO 3.6m Telescope at La Silla, and the High
Resolution Echelle Spectrometer (HIRES) on the Keck I Telescope. An
optical spectrum of one star was collected previously using the Robert
G. Tull Coude Spectrograph at the Harlan J. Smith Telescope at McDonald
Observatory (see the details in Roederer+ 2014, J/AJ/147/136). <P />(3
data files).
---------------------------------------------------------
Title: Carbon and oxygen in metal-poor halo stars
Authors: Amarsi, A. M.; Nissen, P. E.; Asplund, M.; Lind, K.; Barklem,
P. S.
2019A&A...622L...4A Altcode: 2019arXiv190103592A
Carbon and oxygen are key tracers of the Galactic chemical evolution;
in particular, a reported upturn in [C/O] towards decreasing [O/H]
in metal-poor halo stars could be a signature of nucleosynthesis by
massive Population III stars. We reanalyse carbon, oxygen, and iron
abundances in 39 metal-poor turn-off stars. For the first time, we
take into account 3D hydrodynamic effects together with departures
from local thermodynamic equilibrium (LTE) when determining both the
stellar parameters and the elemental abundances, by deriving effective
temperatures from 3D non-LTE Hβ profiles, surface gravities from Gaia
parallaxes, iron abundances from 3D LTE Fe II equivalent widths, and
carbon and oxygen abundances from 3D non-LTE C I and O I equivalent
widths. We find that [C/Fe] stays flat with [Fe/H], whereas [O/Fe]
increases linearly up to 0.75 dex with decreasing [Fe/H] down to -3.0
dex. Therefore [C/O] monotonically decreases towards decreasing [C/H],
in contrast to previous findings, mainly because the non-LTE effects
for O I at low [Fe/H] are weaker with our improved calculations. <P
/>Tables 1-4 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/L4">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/L4</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Carbon and oxygen in metal-poor
halo stars (Amarsi+, 2019)
Authors: Amarsi, A. M.; Nissen, P. E.; Asplund, M.; Lind, K.; Barklem,
P. S.
2019yCat..36229004A Altcode:
table1.dat contains stellar parameters and abundances. table2.dat
contains line-by-line equivalent widths and abundances for The FeII
lines used in this work. table3.dat contains line-by-line equivalent
widths and abundances for the CI lines used in this work. table4.dat
contains line-by-line equivalent widths and abundances for the OI
lines used in this work. <P />(4 data files).
---------------------------------------------------------
Title: A collection of model stellar spectra for spectral types B
to early-M
Authors: Allende Prieto, C.; Koesterke, L.; Hubeny, I.; Bautista,
M. A.; Barklem, P. S.; Nahar, S. N.
2018A&A...618A..25A Altcode: 2018arXiv180706049A
Context. Models of stellar spectra are necessary for interpreting light
from individual stars, planets, integrated stellar populations, nebulae,
and the interstellar medium. <BR /> Aims: We provide a comprehensive
and homogeneous collection of synthetic spectra for a wide range of
atmospheric parameters and chemical compositions. <BR /> Methods:
We compile atomic and molecular data from the literature. We adopt
the largest and most recent set of ATLAS9 model atmospheres, and use
the radiative code ASSɛT. <BR /> Results: The resulting collection
of spectra is made publicly available at medium and high-resolution
(R ≡ λ/δλ = 10 000, 100 000 and 300 000) spectral grids,
which include variations in effective temperature between 3500 K
and 30 000 K, surface gravity (0 ≤ log g ≤ 5), and metallicity
(-5 ≤ [Fe/H] ≤ +0:5), spanning the wavelength interval 120-6500
nm. A second set of denser grids with additional dimensions, [α/Fe]
and micro-turbulence, are also provided (covering 200-2500 nm). We
compare models with observations for a few representative cases. <P
/>Data files are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A25">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A25</A>
---------------------------------------------------------
Title: Gaia Data Release 2. Observations of solar system objects
Authors: Gaia Collaboration; Spoto, F.; Tanga, P.; Mignard, F.;
Berthier, J.; Carry, B.; Cellino, A.; Dell'Oro, A.; Hestroffer, D.;
Muinonen, K.; Pauwels, T.; Petit, J. -M.; David, P.; De Angeli, F.;
Delbo, M.; Frézouls, B.; Galluccio, L.; Granvik, M.; Guiraud, J.;
Hernández, J.; Ordénovic, C.; Portell, J.; Poujoulet, E.; Thuillot,
W.; Walmsley, G.; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de
Bruijne, J. H. J.; Babusiaux, C.; Bailer-Jones, C. A. L.; Biermann,
M.; Evans, D. W.; Eyer, L.; Jansen, F.; Jordi, C.; Klioner, S. A.;
Lammers, U.; Lindegren, L.; Luri, X.; Panem, C.; Pourbaix, D.; Randich,
S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; van Leeuwen, F.;
Walton, N. A.; Arenou, F.; Bastian, U.; Cropper, M.; Drimmel, R.;
Katz, D.; Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castañeda, J.;
Chaoul, L.; Cheek, N.; Fabricius, C.; Guerra, R.; Holl, B.; Masana,
E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Panuzzo, P.; Riello,
M.; Seabroke, G. M.; Thévenin, F.; Gracia-Abril, G.; Comoretto,
G.; Garcia-Reinaldos, M.; Teyssier, D.; Altmann, M.; Andrae, R.;
Audard, M.; Bellas-Velidis, I.; Benson, K.; Blomme, R.; Burgess, P.;
Busso, G.; Clementini, G.; Clotet, M.; Creevey, O.; Davidson, M.; De
Ridder, J.; Delchambre, L.; Ducourant, C.; Fernández-Hernández, J.;
Fouesneau, M.; Frémat, Y.; García-Torres, M.; González-Núñez,
J.; González-Vidal, J. J.; Gosset, E.; Guy, L. P.; Halbwachs,
J. -L.; Hambly, N. C.; Harrison, D. L.; Hodgkin, S. T.; Hutton,
A.; Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn,
A. J.; Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.; Lö, W.;
Manteiga, M.; Marrese, P. M.; Martín-Fleitas, J. M.; Moitinho, A.;
Mora, A.; Osinde, J.; Pancino, E.; Recio-Blanco, A.; Richards, P. J.;
Rimoldini, L.; Robin, A. C.; Sarro, L. M.; Siopis, C.; Smith, M.;
Sozzetti, A.; Süveges, M.; Torra, J.; van Reeven, W.; Abbas, U.;
Abreu Aramburu, A.; Accart, S.; Aerts, C.; Altavilla, G.; Álvarez,
M. A.; Alvarez, R.; Alves, J.; Anderson, R. I.; Andrei, A. H.; Anglada
Varela, E.; Antiche, E.; Antoja, T.; Arcay, B.; Astraatmadja, T. L.;
Bach, N.; Baker, S. G.; Balaguer-Núñez, L.; Balm, P.; Barache,
C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem, P. S.; Barrado,
D.; Barros, M.; Barstow, M. A.; Bartholomé Muñoz, L.; Bassilana,
J. -L.; Becciani, U.; Bellazzini, M.; Berihuete, A.; Bertone, S.;
Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.; Boch, T.; Boeche, C.;
Bombrun, A.; Borrachero, R.; Bossini, D.; Bouquillon, S.; Bourda, G.;
Bragaglia, A.; Bramante, L.; Breddels, M. A.; Bressan, A.; Brouillet,
N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli, B.; Burlacu, A.;
Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau, E.; Cancelliere,
R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo, R.; Carlucci, T.;
Carrasco, J. M.; Casamiquela, L.; Castellani, M.; Castro-Ginard,
A.; Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza, G.; Costigan,
G.; Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypers, J.;
Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, M.; de Laverny, P.;
De Luise, F.; De March, R.; de Souza, R.; de Torres, A.; Debosscher,
J.; del Pozo, E.; Delgado, A.; Delgado, H. E.; Diakite, S.; Diener,
C.; Distefano, E.; Dolding, C.; Drazinos, P.; Durán, J.; Edvardsson,
B.; Enke, H.; Eriksson, K.; Esquej, P.; Eynard Bontemps, G.; Fabre,
C.; Fabrizio, M.; Faigler, S.; Falcão, A. J.; Farràs Casas, M.;
Federici, L.; Fedorets, G.; Fernique, P.; Figueras, F.; Filippi, F.;
Findeisen, K.; Fonti, A.; Fraile, E.; Fraser, M.; Gai, M.; Galleti, S.;
Garabato, D.; García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel,
A.; Gavras, P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore, G.;
Girona, S.; Giuffrida, G.; Glass, F.; Gomes, M.; Gueguen, A.; Guerrier,
A.; Gutié, R.; Haigron, R.; Hatzidimitriou, D.; Hauser, M.; Haywood,
M.; Heiter, U.; Helmi, A.; Heu, J.; Hilger, T.; Hobbs, D.; Hofmann,
W.; Holland, G.; Huckle, H. E.; Hypki, A.; Icardi, V.; Janßen, K.;
Jevardat de Fombelle, G.; Jonker, P. G.; Juhász, Á. L.; Julbe,
F.; Karampelas, A.; Kewley, A.; Klar, J.; Kochoska, A.; Kohley, R.;
Kolenberg, K.; Kontizas, M.; Kontizas, E.; Koposov, S. E.; Kordopatis,
G.; Kostrzewa-Rutkowska, Z.; Koubsky, P.; Lambert, S.; Lanza, A. F.;
Lasne, Y.; Lavigne, J. -B.; Le Fustec, Y.; Le Poncin-Lafitte, C.;
Lebreton, Y.; Leccia, S.; Leclerc, N.; Lecoeur-Taibi, I.; Lenhardt,
H.; Leroux, F.; Liao, S.; Licata, E.; Lindstrøm, H. E. P.; Lister,
T. A.; Livanou, E.; Lobel, A.; López, M.; Managau, S.; Mann, R. G.;
Mantelet, G.; Marchal, O.; Marchant, J. M.; Marconi, M.; Marinoni,
S.; Marschalkó, G.; Marshall, D. J.; Martino, M.; Marton, G.; Mary,
N.; Massari, D.; Matijevič, G.; Mazeh, T.; McMillan, P. J.; Messina,
S.; Michalik, D.; Millar, N. R.; Molina, D.; Molinaro, R.; Molnár,
L.; Montegriffo, P.; Mor, R.; Morbidelli, R.; Morel, T.; Morris, D.;
Mulone, A. F.; Muraveva, T.; Musella, I.; Nelemans, G.; Nicastro, L.;
Noval, L.; O'Mullane, W.; Ordóñez-Blanco, D.; Osborne, P.; Pagani,
C.; Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.; Panahi, A.;
Pawlak, M.; Piersimoni, A. M.; Pineau, F. -X.; Plachy, E.; Plum, G.;
Poggio, E.; Prša, A.; Pulone, L.; Racero, E.; Ragaini, S.; Rambaux,
N.; Ramos-Lerate, M.; Regibo, S.; Reylé, C.; Riclet, F.; Ripepi,
V.; Riva, A.; Rivard, A.; Rixon, G.; Roegiers, T.; Roelens, M.;
Romero-Gómez, M.; Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski,
G.; Sagristà Sellés, T.; Sahlmann, J.; Salgado, J.; Salguero, E.;
Sanna, N.; Santana-Ros, T.; Sarasso, M.; Savietto, H.; Schultheis, M.;
Sciacca, E.; Segol, M.; Segovia, J. C.; Ségransan, D.; Shih, I. -C.;
Siltala, L.; Silva, A. F.; Smart, R. L.; Smith, K. W.; Solano, E.;
Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.; Spagna, A.;
Stampa, U.; Steele, I. A.; Steidelmüller, H.; Stephenson, C. A.;
Stoev, H.; Suess, F. F.; Surdej, J.; Szabados, L.; Szegedi-Elek, E.;
Tapiador, D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.;
Terrett, D.; Teyssandier, P.; Titarenko, A.; Torra Clotet, F.; Turon,
C.; Ulla, A.; Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini, G.;
Valette, V.; van Elteren, A.; Van Hemelryck, E.; van Leeuwen, M.;
Vaschetto, M.; Vecchiato, A.; Veljanoski, J.; Viala, Y.; Vicente,
D.; Vogt, S.; von Essen, C.; Voss, H.; Votruba, V.; Voutsinas, S.;
Weiler, M.; Wertz, O.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.;
Žerjal, M.; Ziaeepour, H.; Zorec, J.; Zschocke, S.; Zucker, S.;
Zurbach, C.; Zwitter, T.
2018A&A...616A..13G Altcode: 2018arXiv180409379G
Context. The Gaia spacecraft of the European Space Agency (ESA)
has been securing observations of solar system objects (SSOs) since
the beginning of its operations. Data Release 2 (DR2) contains the
observations of a selected sample of 14,099 SSOs. These asteroids have
been already identified and have been numbered by the Minor Planet
Center repository. Positions are provided for each Gaia observation at
CCD level. As additional information, complementary to astrometry, the
apparent brightness of SSOs in the unfiltered G band is also provided
for selected observations. <BR /> Aims: We explain the processing of SSO
data, and describe the criteria we used to select the sample published
in Gaia DR2. We then explore the data set to assess its quality. <BR />
Methods: To exploit the main data product for the solar system in Gaia
DR2, which is the epoch astrometry of asteroids, it is necessary to take
into account the unusual properties of the uncertainty, as the position
information is nearly one-dimensional. When this aspect is handled
appropriately, an orbit fit can be obtained with post-fit residuals
that are overall consistent with the a-priori error model that was used
to define individual values of the astrometric uncertainty. The role
of both random and systematic errors is described. The distribution
of residuals allowed us to identify possible contaminants in the
data set (such as stars). Photometry in the G band was compared
to computed values from reference asteroid shapes and to the flux
registered at the corresponding epochs by the red and blue photometers
(RP and BP). <BR /> Results: The overall astrometric performance is
close to the expectations, with an optimal range of brightness G 12 -
17. In this range, the typical transit-level accuracy is well below
1 mas. For fainter asteroids, the growing photon noise deteriorates
the performance. Asteroids brighter than G 12 are affected by a lower
performance of the processing of their signals. The dramatic improvement
brought by Gaia DR2 astrometry of SSOs is demonstrated by comparisons
to the archive data and by preliminary tests on the detection of subtle
non-gravitational effects.
---------------------------------------------------------
Title: Inelastic O+H collisions and the O I 777 nm solar
centre-to-limb variation
Authors: Amarsi, A. M.; Barklem, P. S.; Asplund, M.; Collet, R.;
Zatsarinny, O.
2018A&A...616A..89A Altcode: 2018arXiv180310531A
The O I 777 nm triplet is a key diagnostic of oxygen abundances
in the atmospheres of FGK-type stars; however, it is sensitive to
departures from local thermodynamic equilibrium (LTE). The accuracy
of non-LTE line formation calculations has hitherto been limited by
errors in the inelastic O+H collisional rate coefficients; several
recent studies have used the Drawin recipe, albeit with a correction
factor S<SUB>H</SUB> that is calibrated to the solar centre-to-limb
variation of the triplet. We present a new model oxygen atom that
incorporates inelastic O+H collisional rate coefficients using an
asymptotic two-electron model based on linear combinations of atomic
orbitals, combined with a free electron model based on the impulse
approximation. Using a 3D hydrodynamic STAGGER model solar atmosphere
and 3D non-LTE line formation calculations, we demonstrate that
this physically motivated approach is able to reproduce the solar
centre-to-limb variation of the triplet to 0.02 dex, without any
calibration of the inelastic collisional rate coefficients or other
free parameters. We infer log ɛ<SUB>O</SUB> = 8.69 ± 0.03 from the
triplet alone, strengthening the case for a low solar oxygen abundance.
---------------------------------------------------------
Title: Gaia Data Release 2. The celestial reference frame (Gaia-CRF2)
Authors: Gaia Collaboration; Mignard, F.; Klioner, S. A.; Lindegren,
L.; Hernández, J.; Bastian, U.; Bombrun, A.; Hobbs, D.; Lammers, U.;
Michalik, D.; Ramos-Lerate, M.; Biermann, M.; Fernández-Hernández,
J.; Geyer, R.; Hilger, T.; Siddiqui, H. I.; Steidelmüller, H.;
Babusiaux, C.; Barache, C.; Lambert, S.; Andrei, A. H.; Bourda, G.;
Charlot, P.; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne,
J. H. J.; Bailer-Jones, C. A. L.; Evans, D. W.; Eyer, L.; Jansen, F.;
Jordi, C.; Luri, X.; Panem, C.; Pourbaix, D.; Randich, S.; Sartoretti,
P.; Soubiran, C.; van Leeuwen, F.; Walton, N. A.; Arenou, F.; Cropper,
M.; Drimmel, R.; Katz, D.; Lattanzi, M. G.; Bakker, J.; Cacciari,
C.; Castañeda, J.; Chaoul, L.; Cheek, N.; De Angeli, F.; Fabricius,
C.; Guerra, R.; Holl, B.; Masana, E.; Messineo, R.; Mowlavi, N.;
Nienartowicz, K.; Panuzzo, P.; Portell, J.; Riello, M.; Seabroke,
G. M.; Tanga, P.; Thévenin, F.; Gracia-Abril, G.; Comoretto,
G.; Garcia-Reinaldos, M.; Teyssier, D.; Altmann, M.; Andrae, R.;
Audard, M.; Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme,
R.; Burgess, P.; Busso, G.; Carry, B.; Cellino, A.; Clementini, G.;
Clotet, M.; Creevey, O.; Davidson, M.; De Ridder, J.; Delchambre, L.;
Dell'Oro, A.; Ducourant, C.; Fouesneau, M.; Frémat, Y.; Galluccio,
L.; García-Torres, M.; González-Núñez, J.; González-Vidal, J. J.;
Gosset, E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison,
D. L.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.; Jasniewicz, G.;
Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.; Krone-Martins, A.;
Lanzafame, A. C.; Lebzelter, T.; Löffler, W.; Manteiga, M.; Marrese,
P. M.; Martín-Fleitas, J. M.; Moitinho, A.; Mora, A.; Muinonen, K.;
Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J. -M.; Recio-Blanco, A.;
Richards, P. J.; Rimoldini, L.; Robin, A. C.; Sarro, L. M.; Siopis,
C.; Smith, M.; Sozzetti, A.; Süveges, M.; Torra, J.; van Reeven,
W.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts, C.; Altavilla,
G.; Álvarez, M. A.; Alvarez, R.; Alves, J.; Anderson, R. I.; Anglada
Varela, E.; Antiche, E.; Antoja, T.; Arcay, B.; Astraatmadja, T. L.;
Bach, N.; Baker, S. G.; Balaguer-Núñez, L.; Balm, P.; Barata, C.;
Barbato, D.; Barblan, F.; Barklem, P. S.; Barrado, D.; Barros, M.;
Barstow, M. A.; Bartholomé Muñoz, L.; Bassilana, J. -L.; Becciani,
U.; Bellazzini, M.; Berihuete, A.; Bertone, S.; Bianchi, L.; Bienaymé,
O.; Blanco-Cuaresma, S.; Boch, T.; Boeche, C.; Borrachero, R.;
Bossini, D.; Bouquillon, S.; Bragaglia, A.; Bramante, L.; Breddels,
M. A.; Bressan, A.; Brouillet, N.; Brüsemeister, T.; Brugaletta, E.;
Bucciarelli, B.; Burlacu, A.; Busonero, D.; Butkevich, A. G.; Buzzi,
R.; Caffau, E.; Cancelliere, R.; Cannizzaro, G.; Cantat-Gaudin,
T.; Carballo, R.; Carlucci, T.; Carrasco, J. M.; Casamiquela, L.;
Castellani, M.; Castro-Ginard, A.; Chemin, L.; Chiavassa, A.; Cocozza,
G.; Costigan, G.; Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.;
Cuypers, J.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.;
David, M.; de Laverny, P.; De Luise, F.; De March, R.; de Souza, R.;
de Torres, A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.;
Delgado, H. E.; Diakite, S.; Diener, C.; Distefano, E.; Dolding, C.;
Drazinos, P.; Durán, J.; Edvardsson, B.; Enke, H.; Eriksson, K.;
Esquej, P.; Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Faigler,
S.; Falcão, A. J.; Farràs Casas, M.; Federici, L.; Fedorets, G.;
Fernique, P.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.;
Fraile, E.; Fraser, M.; Frézouls, B.; Gai, M.; Galleti, S.; Garabato,
D.; García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel, A.; Gavras,
P.; Gerssen, J.; Giacobbe, P.; Gilmore, G.; Girona, S.; Giuffrida, G.;
Glass, F.; Gomes, M.; Granvik, M.; Gueguen, A.; Guerrier, A.; Guiraud,
J.; Gutié, R.; Haigron, R.; Hatzidimitriou, D.; Hauser, M.; Haywood,
M.; Heiter, U.; Helmi, A.; Heu, J.; Hofmann, W.; Holland, G.; Huckle,
H. E.; Hypki, A.; Icardi, V.; Janßen, K.; Jevardat de Fombelle, G.;
Jonker, P. G.; Juhász, A. L.; Julbe, F.; Karampelas, A.; Kewley,
A.; Klar, J.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.;
Kontizas, E.; Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska,
Z.; Koubsky, P.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; López,
M.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant,
J. M.; Marconi, M.; Marinoni, S.; Marschalkó, G.; Marshall, D. J.;
Martino, M.; Marton, G.; Mary, N.; Massari, D.; Matijevič, G.;
Mazeh, T.; McMillan, P. J.; Messina, S.; Millar, N. R.; Molina, D.;
Molinaro, R.; Molnár, L.; Montegriffo, P.; Mor, R.; Morbidelli,
R.; Morel, T.; Morris, D.; Mulone, A. F.; Muraveva, T.; Musella, I.;
Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane, W.; Ordénovic, C.;
Ordóñez-Blanco, D.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler,
F.; Palacin, H.; Palaversa, L.; Panahi, A.; Pawlak, M.; Piersimoni,
A. M.; Pineau, F. -X.; Plachy, E.; Plum, G.; Poggio, E.; Poujoulet,
E.; Prša, A.; Pulone, L.; Racero, E.; Ragaini, S.; Rambaux, N.;
Regibo, S.; Reylé, C.; Riclet, F.; Ripepi, V.; Riva, A.; Rivard,
A.; Rixon, G.; Roegiers, T.; Roelens, M.; Romero-Gómez, M.; Rowell,
N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés, T.;
Sahlmann, J.; Salgado, J.; Salguero, E.; Sanna, N.; Santana-Ros, T.;
Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.;
Segovia, J. C.; Ségransan, D.; Shih, I. -C.; Siltala, L.; Silva,
A. F.; Smart, R. L.; Smith, K. W.; Solano, E.; Solitro, F.; Sordo,
R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa, U.;
Steele, I. A.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Surdej,
J.; Szabados, L.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran,
G.; Taylor, M. B.; Teixeira, R.; Terrett, D.; Teyssandier, P.;
Thuillot, W.; Titarenko, A.; Torra Clotet, F.; Turon, C.; Ulla,
A.; Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini, G.; Valette,
V.; van Elteren, A.; Van Hemelryck, E.; van Leeuwen, M.; Vaschetto,
M.; Vecchiato, A.; Veljanoski, J.; Viala, Y.; Vicente, D.; Vogt, S.;
von Essen, C.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.;
Weiler, M.; Wertz, O.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.;
Žerjal, M.; Ziaeepour, H.; Zorec, J.; Zschocke, S.; Zucker, S.;
Zurbach, C.; Zwitter, T.
2018A&A...616A..14G Altcode: 2018arXiv180409377M
Context. The second release of Gaia data (Gaia DR2) contains the
astrometric parameters for more than half a million quasars. This set
defines a kinematically non-rotating reference frame in the optical
domain. A subset of these quasars have accurate VLBI positions
that allow the axes of the reference frame to be aligned with the
International Celestial Reference System (ICRF) radio frame. <BR
/> Aims: We describe the astrometric and photometric properties of
the quasars that were selected to represent the celestial reference
frame of Gaia DR2 (Gaia-CRF2), and to compare the optical and radio
positions for sources with accurate VLBI positions. <BR /> Methods:
Descriptive statistics are used to characterise the overall properties
of the quasar sample. Residual rotation and orientation errors and
large-scale systematics are quantified by means of expansions in vector
spherical harmonics. Positional differences are calculated relative to
a prototype version of the forthcoming ICRF3. <BR /> Results: Gaia-CRF2
consists of the positions of a sample of 556 869 sources in Gaia DR2,
obtained from a positional cross-match with the ICRF3-prototype and
AllWISE AGN catalogues. The sample constitutes a clean, dense, and
homogeneous set of extragalactic point sources in the magnitude range
G ≃ 16 to 21 mag with accurately known optical positions. The median
positional uncertainty is 0.12 mas for G < 18 mag and 0.5 mas at
G = mag. Large-scale systematics are estimated to be in the range 20
to 30 μas. The accuracy claims are supported by the parallaxes and
proper motions of the quasars in Gaia DR2. The optical positions for
a subset of 2820 sources in common with the ICRF3-prototype show very
good overall agreement with the radio positions, but several tens of
sources have significantly discrepant positions. <BR /> Conclusions:
Based on less than 40% of the data expected from the nominal Gaia
mission, Gaia-CRF2 is the first realisation of a non-rotating global
optical reference frame that meets the ICRS prescriptions, meaning
that it is built only on extragalactic sources. Its accuracy matches
the current radio frame of the ICRF, but the density of sources in
all parts of the sky is much higher, except along the Galactic equator.
---------------------------------------------------------
Title: Gaia Data Release 2. Mapping the Milky Way disc kinematics
Authors: Gaia Collaboration; Katz, D.; Antoja, T.; Romero-Gómez, M.;
Drimmel, R.; Reylé, C.; Seabroke, G. M.; Soubiran, C.; Babusiaux,
C.; Di Matteo, P.; Figueras, F.; Poggio, E.; Robin, A. C.; Evans,
D. W.; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne,
J. H. J.; Bailer-Jones, C. A. L.; Biermann, M.; Eyer, L.; Jansen,
F.; Jordi, C.; Klioner, S. A.; Lammers, U.; Lindegren, L.; Luri,
X.; Mignard, F.; Panem, C.; Pourbaix, D.; Randich, S.; Sartoretti,
P.; Siddiqui, H. I.; van Leeuwen, F.; Walton, N. A.; Arenou, F.;
Bastian, U.; Cropper, M.; Lattanzi, M. G.; Bakker, J.; Cacciari,
C.; Casta n, J.; Chaoul, L.; Cheek, N.; De Angeli, F.; Fabricius,
C.; Guerra, R.; Holl, B.; Masana, E.; Messineo, R.; Mowlavi, N.;
Nienartowicz, K.; Panuzzo, P.; Portell, J.; Riello, M.; Tanga, P.;
Thévenin, F.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.;
Teyssier, D.; Altmann, M.; Andrae, R.; Audard, M.; Bellas-Velidis,
I.; Benson, K.; Berthier, J.; Blomme, R.; Burgess, P.; Busso, G.;
Carry, B.; Cellino, A.; Clementini, G.; Clotet, M.; Creevey, O.;
Davidson, M.; De Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant,
C.; Fernández-Hernández, J.; Fouesneau, M.; Frémat, Y.; Galluccio,
L.; García-Torres, M.; González-Núñez, J.; González-Vidal, J. J.;
Gosset, E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison,
D. L.; Hernández, J.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.;
Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.;
Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.; Löffler, W.;
Manteiga, M.; Marrese, P. M.; Martín-Fleitas, J. M.; Moitinho, A.;
Mora, A.; Muinonen, K.; Osinde, J.; Pancino, E.; Pauwels, T.; Petit,
J. -M.; Recio-Blanco, A.; Richards, P. J.; Rimoldini, L.; Sarro,
L. M.; Siopis, C.; Smith, M.; Sozzetti, A.; Süveges, M.; Torra, J.;
van Reeven, W.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts, C.;
Altavilla, G.; Álvarez, M. A.; Alvarez, R.; Alves, J.; Anderson,
R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Arcay, B.;
Astraatmadja, T. L.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.;
Balm, P.; Barache, C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem,
P. S.; Barrado, D.; Barros, M.; Barstow, M. A.; Bartholomé Muñoz,
L.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.; Berihuete, A.;
Bertone, S.; Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.; Boch,
T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bossini, D.; Bouquillon,
S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Breddels, M. A.; Bressan,
A.; Brouillet, N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli,
B.; Burlacu, A.; Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau,
E.; Cancelliere, R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo,
R.; Carlucci, T.; Carrasco, J. M.; Casamiquela, L.; Castellani, M.;
Castro-Ginard, A.; Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza,
G.; Costigan, G.; Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.;
Cuypers, J.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.;
David, M.; de Laverny, P.; De Luise, F.; De March, R.; de Souza, R.;
de Torres, A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.;
Delgado, H. E.; Diakite, S.; Diener, C.; Distefano, E.; Dolding, C.;
Drazinos, P.; Durán, J.; Edvardsson, B.; Enke, H.; Eriksson, K.;
Esquej, P.; Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Faigler,
S.; Falc a, A. J.; Farràs Casas, M.; Federici, L.; Fedorets, G.;
Fernique, P.; Filippi, F.; Findeisen, K.; Fonti, A.; Fraile, E.;
Fraser, M.; Frézouls, B.; Gai, M.; Galleti, S.; Garabato, D.;
García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel, A.; Gavras,
P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore, G.; Girona,
S.; Giuffrida, G.; Glass, F.; Gomes, M.; Granvik, M.; Gueguen, A.;
Guerrier, A.; Guiraud, J.; Gutié, R.; Haigron, R.; Hatzidimitriou,
D.; Hauser, M.; Haywood, M.; Heiter, U.; Helmi, A.; Heu, J.; Hilger,
T.; Hobbs, D.; Hofmann, W.; Holland, G.; Huckle, H. E.; Hypki, A.;
Icardi, V.; Janßen, K.; Jevardat de Fombelle, G.; Jonker, P. G.;
Juhász, Á. L.; Julbe, F.; Karampelas, A.; Kewley, A.; Klar, J.;
Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.; Kontizas, E.;
Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.; Koubsky, P.;
Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; López,
M.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant,
J. M.; Marconi, M.; Marinoni, S.; Marschalkó, G.; Marshall, D. J.;
Martino, M.; Marton, G.; Mary, N.; Massari, D.; Matijevič, G.; Mazeh,
T.; McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Molina,
D.; Molinaro, R.; Molnár, L.; Montegriffo, P.; Mor, R.; Morbidelli,
R.; Morel, T.; Morris, D.; Mulone, A. F.; Muraveva, T.; Musella, I.;
Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane, W.; Ordénovic, C.;
Ordóñez-Blanco, D.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler,
F.; Palacin, H.; Palaversa, L.; Panahi, A.; Pawlak, M.; Piersimoni,
A. M.; Pineau, F. -X.; Plachy, E.; Plum, G.; Poujoulet, E.; Prša,
A.; Pulone, L.; Racero, E.; Ragaini, S.; Rambaux, N.; Ramos-Lerate,
M.; Regibo, S.; Riclet, F.; Ripepi, V.; Riva, A.; Rivard, A.; Rixon,
G.; Roegiers, T.; Roelens, M.; Rowell, N.; Royer, F.; Ruiz-Dern,
L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann, J.; Salgado, J.;
Salguero, E.; Sanna, N.; Santana-Ros, T.; Sarasso, M.; Savietto, H.;
Schultheis, M.; Sciacca, E.; Segol, M.; Segovia, J. C.; Ségransan,
D.; Shih, I. -C.; Siltala, L.; Silva, A. F.; Smart, R. L.; Smith,
K. W.; Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay,
J.; Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmüller,
H.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Surdej, J.; Szabados,
L.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor,
M. B.; Teixeira, R.; Terrett, D.; Teyssandier, P.; Thuillot, W.;
Titarenko, A.; Torra Clotet, F.; Turon, C.; Ulla, A.; Utrilla, E.;
Uzzi, S.; Vaillant, M.; Valentini, G.; Valette, V.; van Elteren,
A.; Van Hemelryck, E.; van Leeuwen, M.; Vaschetto, M.; Vecchiato,
A.; Veljanoski, J.; Viala, Y.; Vicente, D.; Vogt, S.; von Essen, C.;
Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Wertz,
O.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Ziaeepour,
H.; Zorec, J.; Zschocke, S.; Zucker, S.; Zurbach, C.; Zwitter, T.
2018A&A...616A..11G Altcode: 2018arXiv180409380G
Context. The second Gaia data release (Gaia DR2) contains high-precision
positions, parallaxes, and proper motions for 1.3 billion sources as
well as line-of-sight velocities for 7.2 million stars brighter than
G<SUB>RVS</SUB> = 12 mag. Both samples provide a full sky coverage. <BR
/> Aims: To illustrate the potential of Gaia DR2, we provide a first
look at the kinematics of the Milky Way disc, within a radius of several
kiloparsecs around the Sun. <BR /> Methods: We benefit for the first
time from a sample of 6.4 million F-G-K stars with full 6D phase-space
coordinates, precise parallaxes (σ<SUB>ϖ</SUB>/ϖ ≤ 20%), and
precise Galactic cylindrical velocities (median uncertainties of 0.9-1.4
km s<SUP>-1</SUP> and 20% of the stars with uncertainties smaller than
1 km s<SUP>-1</SUP> on all three components). From this sample, we
extracted a sub-sample of 3.2 million giant stars to map the velocity
field of the Galactic disc from 5 kpc to 13 kpc from the Galactic
centre and up to 2 kpc above and below the plane. We also study the
distribution of 0.3 million solar neighbourhood stars (r < 200 pc),
with median velocity uncertainties of 0.4 km s<SUP>-1</SUP>, in velocity
space and use the full sample to examine how the over-densities evolve
in more distant regions. <BR /> Results: Gaia DR2 allows us to draw 3D
maps of the Galactocentric median velocities and velocity dispersions
with unprecedented accuracy, precision, and spatial resolution. The
maps show the complexity and richness of the velocity field of the
galactic disc. We observe streaming motions in all the components of
the velocities as well as patterns in the velocity dispersions. For
example, we confirm the previously reported negative and positive
galactocentric radial velocity gradients in the inner and outer disc,
respectively. Here, we see them as part of a non-axisymmetric kinematic
oscillation, and we map its azimuthal and vertical behaviour. We also
witness a new global arrangement of stars in the velocity plane of
the solar neighbourhood and in distant regions in which stars are
organised in thin substructures with the shape of circular arches
that are oriented approximately along the horizontal direction in the
U - V plane. Moreover, in distant regions, we see variations in the
velocity substructures more clearly than ever before, in particular,
variations in the velocity of the Hercules stream. <BR /> Conclusions:
Gaia DR2 provides the largest existing full 6D phase-space coordinates
catalogue. It also vastly increases the number of available distances
and transverse velocities with respect to Gaia DR1. Gaia DR2 offers
a great wealth of information on the Milky Way and reveals clear
non-axisymmetric kinematic signatures within the Galactic disc, for
instance. It is now up to the astronomical community to explore its
full potential.
---------------------------------------------------------
Title: Gaia Data Release 2. Observational Hertzsprung-Russell diagrams
Authors: Gaia Collaboration; Babusiaux, C.; van Leeuwen, F.;
Barstow, M. A.; Jordi, C.; Vallenari, A.; Bossini, D.; Bressan,
A.; Cantat-Gaudin, T.; van Leeuwen, M.; Brown, A. G. A.; Prusti,
T.; de Bruijne, J. H. J.; Bailer-Jones, C. A. L.; Biermann, M.;
Evans, D. W.; Eyer, L.; Jansen, F.; Klioner, S. A.; Lammers, U.;
Lindegren, L.; Luri, X.; Mignard, F.; Panem, C.; Pourbaix, D.;
Randich, S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; Walton,
N. A.; Arenou, F.; Bastian, U.; Cropper, M.; Drimmel, R.; Katz, D.;
Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castañeda, J.; Chaoul,
L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra, R.; Holl, B.;
Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Panuzzo,
P.; Portell, J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thévenin,
F.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Teyssier,
D.; Altmann, M.; Andrae, R.; Audard, M.; Bellas-Velidis, I.; Benson,
K.; Berthier, J.; Blomme, R.; Burgess, P.; Busso, G.; Carry, B.;
Cellino, A.; Clementini, G.; Clotet, M.; Creevey, O.; Davidson,
M.; De Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.;
Fernández-Hernández, J.; Fouesneau, M.; Frémat, Y.; Galluccio, L.;
García-Torres, M.; González-Núñez, J.; González-Vidal, J. J.;
Gosset, E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison,
D. L.; Hernández, J.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.;
Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.;
Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.; Löffler, W.;
Manteiga, M.; Marrese, P. M.; Martín-Fleitas, J. M.; Moitinho, A.;
Mora, A.; Muinonen, K.; Osinde, J.; Pancino, E.; Pauwels, T.; Petit,
J. -M.; Recio-Blanco, A.; Richards, P. J.; Rimoldini, L.; Robin,
A. C.; Sarro, L. M.; Siopis, C.; Smith, M.; Sozzetti, A.; Süveges,
M.; Torra, J.; van Reeven, W.; Abbas, U.; Abreu Aramburu, A.; Accart,
S.; Aerts, C.; Altavilla, G.; Álvarez, M. A.; Alvarez, R.; Alves,
J.; Anderson, R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.;
Antoja, T.; Arcay, B.; Astraatmadja, T. L.; Bach, N.; Baker, S. G.;
Balaguer-Núñez, L.; Balm, P.; Barache, C.; Barata, C.; Barbato,
D.; Barblan, F.; Barklem, P. S.; Barrado, D.; Barros, M.; Bartholomé
Muñoz, L.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.; Berihuete,
A.; Bertone, S.; Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.;
Boch, T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bouquillon, S.;
Bourda, G.; Bragaglia, A.; Bramante, L.; Breddels, M. A.; Brouillet,
N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli, B.; Burlacu, A.;
Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau, E.; Cancelliere,
R.; Cannizzaro, G.; Carballo, R.; Carlucci, T.; Carrasco, J. M.;
Casamiquela, L.; Castellani, M.; Castro-Ginard, A.; Charlot, P.;
Chemin, L.; Chiavassa, A.; Cocozza, G.; Costigan, G.; Cowell,
S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypers, J.; Dafonte, C.;
Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; de Laverny, P.;
De Luise, F.; De March, R.; de Martino, D.; de Souza, R.; de Torres,
A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.; Delgado,
H. E.; Diakite, S.; Diener, C.; Distefano, E.; Dolding, C.; Drazinos,
P.; Durán, J.; Edvardsson, B.; Enke, H.; Eriksson, K.; Esquej, P.;
Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Faigler, S.; Falcão,
A. J.; Farràs Casas, M.; Federici, L.; Fedorets, G.; Fernique,
P.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.; Fraile,
E.; Fraser, M.; Frézouls, B.; Gai, M.; Galleti, S.; Garabato, D.;
García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel, A.; Gavras,
P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore, G.; Girona,
S.; Giuffrida, G.; Glass, F.; Gomes, M.; Granvik, M.; Gueguen, A.;
Guerrier, A.; Guiraud, J.; Gutié, R.; Haigron, R.; Hatzidimitriou,
D.; Hauser, M.; Haywood, M.; Heiter, U.; Helmi, A.; Heu, J.; Hilger,
T.; Hobbs, D.; Hofmann, W.; Holland, G.; Huckle, H. E.; Hypki, A.;
Icardi, V.; Janßen, K.; Jevardat de Fombelle, G.; Jonker, P. G.;
Juhász, Á. L.; Julbe, F.; Karampelas, A.; Kewley, A.; Klar, J.;
Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.; Kontizas, E.;
Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.; Koubsky, P.;
Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; López,
M.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant,
J. M.; Marconi, M.; Marinoni, S.; Marschalkó, G.; Marshall, D. J.;
Martino, M.; Marton, G.; Mary, N.; Massari, D.; Matijevič, G.; Mazeh,
T.; McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Molina,
D.; Molinaro, R.; Molnár, L.; Montegriffo, P.; Mor, R.; Morbidelli,
R.; Morel, T.; Morris, D.; Mulone, A. F.; Muraveva, T.; Musella, I.;
Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane, W.; Ordénovic, C.;
Ordóñez-Blanco, D.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.;
Palacin, H.; Palaversa, L.; Panahi, A.; Pawlak, M.; Piersimoni, A. M.;
Pineau, F. -X.; Plachy, E.; Plum, G.; Poggio, E.; Poujoulet, E.; Prša,
A.; Pulone, L.; Racero, E.; Ragaini, S.; Rambaux, N.; Ramos-Lerate,
M.; Regibo, S.; Reylé, C.; Riclet, F.; Ripepi, V.; Riva, A.; Rivard,
A.; Rixon, G.; Roegiers, T.; Roelens, M.; Romero-Gómez, M.; Rowell,
N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés, T.;
Sahlmann, J.; Salgado, J.; Salguero, E.; Sanna, N.; Santana-Ros, T.;
Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.;
Segovia, J. C.; Ségransan, D.; Shih, I. -C.; Siltala, L.; Silva,
A. F.; Smart, R. L.; Smith, K. W.; Solano, E.; Solitro, F.; Sordo,
R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa,
U.; Steele, I. A.; Steidelmüller, H.; Stephenson, C. A.; Stoev, H.;
Suess, F. F.; Surdej, J.; Szabados, L.; Szegedi-Elek, E.; Tapiador,
D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett,
D.; Teyssandier, P.; Thuillot, W.; Titarenko, A.; Torra Clotet, F.;
Turon, C.; Ulla, A.; Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini,
G.; Valette, V.; van Elteren, A.; Van Hemelryck, E.; Vaschetto, M.;
Vecchiato, A.; Veljanoski, J.; Viala, Y.; Vicente, D.; Vogt, S.;
von Essen, C.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.;
Weiler, M.; Wertz, O.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.;
Žerjal, M.; Ziaeepour, H.; Zorec, J.; Zschocke, S.; Zucker, S.;
Zurbach, C.; Zwitter, T.
2018A&A...616A..10G Altcode: 2018arXiv180409378G
Context. Gaia Data Release 2 provides high-precision astrometry and
three-band photometry for about 1.3 billion sources over the full
sky. The precision, accuracy, and homogeneity of both astrometry and
photometry are unprecedented. <BR /> Aims: We highlight the power of
the Gaia DR2 in studying many fine structures of the Hertzsprung-Russell
diagram (HRD). Gaia allows us to present many different HRDs, depending
in particular on stellar population selections. We do not aim here
for completeness in terms of types of stars or stellar evolutionary
aspects. Instead, we have chosen several illustrative examples. <BR />
Methods: We describe some of the selections that can be made in Gaia
DR2 to highlight the main structures of the Gaia HRDs. We select both
field and cluster (open and globular) stars, compare the observations
with previous classifications and with stellar evolutionary tracks,
and we present variations of the Gaia HRD with age, metallicity, and
kinematics. Late stages of stellar evolution such as hot subdwarfs,
post-AGB stars, planetary nebulae, and white dwarfs are also analysed,
as well as low-mass brown dwarf objects. <BR /> Results: The Gaia HRDs
are unprecedented in both precision and coverage of the various Milky
Way stellar populations and stellar evolutionary phases. Many fine
structures of the HRDs are presented. The clear split of the white
dwarf sequence into hydrogen and helium white dwarfs is presented
for the first time in an HRD. The relation between kinematics and the
HRD is nicely illustrated. Two different populations in a classical
kinematic selection of the halo are unambiguously identified in the
HRD. Membership and mean parameters for a selected list of open
clusters are provided. They allow drawing very detailed cluster
sequences, highlighting fine structures, and providing extremely
precise empirical isochrones that will lead to more insight in
stellar physics. <BR /> Conclusions: Gaia DR2 demonstrates the
potential of combining precise astrometry and photometry for large
samples for studies in stellar evolution and stellar population
and opens an entire new area for HRD-based studies. <P />The full
Table A.1 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A
href="http://cdsarc.u-strasbg.fr">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/616/A10">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/616/A10</A>
---------------------------------------------------------
Title: Chemical characterization of the inner Galactic
bulge:North-South symmetry
Authors: Nandakumar, G.; Ryde, N.; Schultheis, M.; Thorsbro, B.;
Jönsson, H.; Barklem, P. S.; Rich, R. M.; Fragkoudi, F.
2018MNRAS.478.4374N Altcode: 2018MNRAS.tmp.1201N; 2018arXiv180505037N
While the number of stars in the Galactic bulge with detailed
chemical abundance measurements is increasing rapidly, the inner
Galactic bulge (|b| < 2°) remains poorly studied, due to heavy
interstellar absorption and photometric crowding. We have carried out a
high-resolution IR spectroscopic study of 72 M giants in the inner bulge
using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength
range of 2.0818-2.1444 μ m with the resolution of R ∼ 50 000 and have
signal-to-noise ratio of 50:100. Our stars are located along the bulge
minor axis at l = 0°, b= ±0°, ±1°, ±2°, and +3°. Our sample
was analysed in a homogeneous way using the most current K-band line
list. We clearly detect a bimodal metallicity distribution function
with a metal-rich peak at ∼ +0.3 dex and a metal-poor peak at ∼
-0.5 dex and no stars with [Fe/H] > +0.6 dex. The Galactic Centre
field reveals in contrast a mainly metal-rich population with a mean
metallicity of +0.3 dex. We derived [Mg/Fe] and [Si/Fe] abundances
that are consistent with trends from the outer bulge. We confirm for
the supersolar metallicity stars the decreasing trend in [Mg/Fe] and
[Si/Fe] as expected from chemical evolution models. With the caveat of
a relatively small sample, we do not find significant differences in
the chemical abundances between the Northern and the Southern fields;
hence, the evidence is consistent with symmetry in chemistry between
North and South.
---------------------------------------------------------
Title: Gaia Data Release 2. Kinematics of globular clusters and
dwarf galaxies around the Milky Way
Authors: Gaia Collaboration; Helmi, A.; van Leeuwen, F.; McMillan,
P. J.; Massari, D.; Antoja, T.; Robin, A. C.; Lindegren, L.;
Bastian, U.; Arenou, F.; Babusiaux, C.; Biermann, M.; Breddels,
M. A.; Hobbs, D.; Jordi, C.; Pancino, E.; Reylé, C.; Veljanoski,
J.; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne,
J. H. J.; Bailer-Jones, C. A. L.; Evans, D. W.; Eyer, L.; Jansen,
F.; Klioner, S. A.; Lammers, U.; Luri, X.; Mignard, F.; Panem,
C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.;
Soubiran, C.; Walton, N. A.; Cropper, M.; Drimmel, R.; Katz, D.;
Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castañeda, J.; Chaoul,
L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra, R.; Holl, B.;
Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Panuzzo,
P.; Portell, J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thévenin,
F.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Teyssier,
D.; Altmann, M.; Andrae, R.; Audard, M.; Bellas-Velidis, I.; Benson,
K.; Berthier, J.; Blomme, R.; Burgess, P.; Busso, G.; Carry, B.;
Cellino, A.; Clementini, G.; Clotet, M.; Creevey, O.; Davidson,
M.; De Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.;
Fernández-Hernández, J.; Fouesneau, M.; Frémat, Y.; Galluccio, L.;
García-Torres, M.; González-Núñez, J.; González-Vidal, J. J.;
Gosset, E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison,
D. L.; Hernández, J.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.;
Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.;
Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.; Löffler, W.;
Manteiga, M.; Marrese, P. M.; Martín-Fleitas, J. M.; Moitinho, A.;
Mora, A.; Muinonen, K.; Osinde, J.; Pauwels, T.; Petit, J. -M.;
Recio-Blanco, A.; Richards, P. J.; Rimoldini, L.; Sarro, L. M.;
Siopis, C.; Smith, M.; Sozzetti, A.; Süveges, M.; Torra, J.; van
Reeven, W.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts, C.;
Altavilla, G.; Álvarez, M. A.; Alvarez, R.; Alves, J.; Anderson,
R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Arcay, B.;
Astraatmadja, T. L.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.;
Balm, P.; Barache, C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem,
P. S.; Barrado, D.; Barros, M.; Barstow, M. A.; Bartholomé Muñoz,
S.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.; Berihuete, A.;
Bertone, S.; Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.; Boch,
T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bossini, D.; Bouquillon,
S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Bressan, A.; Brouillet,
N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli, B.; Burlacu, A.;
Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau, E.; Cancelliere,
R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo, R.; Carlucci, T.;
Carrasco, J. M.; Casamiquela, L.; Castellani, M.; Castro-Ginard, A.;
Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza, G.; Costigan, G.;
Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypers, J.; Dafonte,
C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; de Laverny,
P.; De Luise, F.; De March, R.; de Martino, D.; de Souza, R.; de
Torres, A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.;
Delgado, H. E.; Di Matteo, P.; Diakite, S.; Diener, C.; Distefano,
E.; Dolding, C.; Drazinos, P.; Durán, J.; Edvardsson, B.; Enke, H.;
Eriksson, K.; Esquej, P.; Eynard Bontemps, G.; Fabre, C.; Fabrizio,
M.; Faigler, S.; Falcão, A. J.; Farràs Casas, M.; Federici, L.;
Fedorets, G.; Fernique, P.; Figueras, F.; Filippi, F.; Findeisen, K.;
Fonti, A.; Fraile, E.; Fraser, M.; Frézouls, B.; Gai, M.; Galleti, S.;
Garabato, D.; García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel,
A.; Gavras, P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore, G.;
Girona, S.; Giuffrida, G.; Glass, F.; Gomes, M.; Granvik, M.; Gueguen,
A.; Guerrier, A.; Guiraud, J.; Gutiérrez-Sánchez, R.; Hofmann,
W.; Holland, G.; Huckle, H. E.; Hypki, A.; Icardi, V.; Janßen, K.;
Jevardat de Fombelle, G.; Jonker, P. G.; Juhász, Á. L.; Julbe,
F.; Karampelas, A.; Kewley, A.; Klar, J.; Kochoska, A.; Kohley, R.;
Kolenberg, K.; Kontizas, M.; Kontizas, E.; Koposov, S. E.; Kordopatis,
G.; Kostrzewa-Rutkowska, Z.; Koubsky, P.; Lambert, S.; Lanza, A. F.;
Lasne, Y.; Lavigne, J. -B.; Le Fustec, Y.; Le Poncin-Lafitte, C.;
Lebreton, Y.; Leccia, S.; Leclerc, N.; Lecoeur-Taibi, I.; Lenhardt,
H.; Leroux, F.; Liao, S.; Licata, E.; Lindstrøm, H. E. P.; Lister,
T. A.; Livanou, E.; Lobel, A.; López, M.; Managau, S.; Mann, R. G.;
Mantelet, G.; Marchal, O.; Marchant, J. M.; Marconi, M.; Marinoni,
S.; Marschalkó, G.; Marshall, D. J.; Martino, M.; Marton, G.; Mary,
N.; Matijevič, G.; Mazeh, T.; Messina, S.; Michalik, D.; Millar,
N. R.; Molina, D.; Molinaro, R.; Molnár, L.; Montegriffo, P.; Mor,
R.; Morbidelli, R.; Morel, T.; Morris, D.; Mulone, A. F.; Muraveva,
T.; Musella, I.; Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane, W.;
Ordénovic, C.; Ordóñez-Blanco, D.; Osborne, P.; Pagani, C.; Pagano,
I.; Pailler, F.; Palacin, H.; Palaversa, L.; Panahi, A.; Pawlak, M.;
Piersimoni, A. M.; Pineau, F. -X.; Plachy, E.; Plum, G.; Poggio, E.;
Poujoulet, E.; Prša, A.; Pulone, L.; Racero, E.; Ragaini, S.; Rambaux,
N.; Ramos-Lerate, M.; Regibo, S.; Riclet, F.; Ripepi, V.; Riva, A.;
Rivard, A.; Rixon, G.; Roegiers, T.; Roelens, M.; Romero-Gómez, M.;
Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés,
T.; Sahlmann, J.; Salgado, J.; Salguero, E.; Sanna, N.; Santana-Ros,
T.; Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol,
M.; Segovia, J. C.; Ségransan, D.; Shih, I. -C.; Siltala, L.; Silva,
A. F.; Smart, R. L.; Smith, K. W.; Solano, E.; Solitro, F.; Sordo,
R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa,
U.; Steele, I. A.; Steidelmüller, H.; Stephenson, C. A.; Stoev, H.;
Suess, F. F.; Surdej, J.; Szabados, L.; Szegedi-Elek, E.; Tapiador,
D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett, D.;
Teyssandier, P.; Thuillot, W.; Titarenko, A.; Torra Clotet, F.;
Turon, C.; Ulla, A.; Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini,
G.; Valette, V.; van Elteren, A.; Van Hemelryck, E.; van Leeuwen,
M.; Vaschetto, M.; Vecchiato, A.; Viala, Y.; Vicente, D.; Vogt, S.;
von Essen, C.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.;
Weiler, M.; Wertz, O.; Wevems, T.; Wyrzykowski, Ł.; Yoldas, A.;
Žerjal, M.; Ziaeepour, H.; Zorec, J.; Zschocke, S.; Zucker, S.;
Zurbach, C.; Zwitter, T.
2018A&A...616A..12G Altcode: 2018arXiv180409381G
Note to the Readers: Following the publication of the <A
href="https://www.aanda.org/articles/aa/full_html/2020/05/aa32698e-18/aa32698e-18.html">corrigendum</A>,
the article was corrected on 15 May 2020. <P />Context. <BR /> Aims:
The goal of this paper is to demonstrate the outstanding quality
of the second data release of the Gaia mission and its power for
constraining many different aspects of the dynamics of the satellites
of the Milky Way. We focus here on determining the proper motions of
75 Galactic globular clusters, nine dwarf spheroidal galaxies, one
ultra-faint system, and the Large and Small Magellanic Clouds. <BR
/> Methods: Using data extracted from the Gaia archive, we derived
the proper motions and parallaxes for these systems, as well as
their uncertainties. We demonstrate that the errors, statistical
and systematic, are relatively well understood. We integrated the
orbits of these objects in three different Galactic potentials, and
characterised their properties. We present the derived proper motions,
space velocities, and characteristic orbital parameters in various
tables to facilitate their use by the astronomical community. <BR />
Results: Our limited and straightforward analyses have allowed us
for example to (i) determine absolute and very precise proper motions
for globular clusters; (ii) detect clear rotation signatures in the
proper motions of at least five globular clusters; (iii) show that
the satellites of the Milky Way are all on high-inclination orbits,
but that they do not share a single plane of motion; (iv) derive a lower
limit for the mass of the Milky Way of 9.1<SUB>-2.6</SUB><SUP>+6.2</SUP>
× 10<SUP>11</SUP> M<SUB>⊙</SUB> based on the assumption that the Leo
I dwarf spheroidal is bound; (v) derive a rotation curve for the Large
Magellanic Cloud based solely on proper motions that is competitive
with line-of-sight velocity curves, now using many orders of magnitude
more sources; and (vi) unveil the dynamical effect of the bar on the
motions of stars in the Large Magellanic Cloud. <BR /> Conclusions: All
these results highlight the incredible power of the Gaia astrometric
mission, and in particular of its second data release. <P />Full
Table D.3 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A
href="http://cdsarc.u-strasbg.fr">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/616/A12">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/616/A12</A>
---------------------------------------------------------
Title: Gaia Data Release 2. Summary of the contents and survey
properties
Authors: Gaia Collaboration; Brown, A. G. A.; Vallenari, A.; Prusti,
T.; de Bruijne, J. H. J.; Babusiaux, C.; Bailer-Jones, C. A. L.;
Biermann, M.; Evans, D. W.; Eyer, L.; Jansen, F.; Jordi, C.; Klioner,
S. A.; Lammers, U.; Lindegren, L.; Luri, X.; Mignard, F.; Panem,
C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.;
Soubiran, C.; van Leeuwen, F.; Walton, N. A.; Arenou, F.; Bastian,
U.; Cropper, M.; Drimmel, R.; Katz, D.; Lattanzi, M. G.; Bakker,
J.; Cacciari, C.; Castañeda, J.; Chaoul, L.; Cheek, N.; De Angeli,
F.; Fabricius, C.; Guerra, R.; Holl, B.; Masana, E.; Messineo, R.;
Mowlavi, N.; Nienartowicz, K.; Panuzzo, P.; Portell, J.; Riello,
M.; Seabroke, G. M.; Tanga, P.; Thévenin, F.; Gracia-Abril, G.;
Comoretto, G.; Garcia-Reinaldos, M.; Teyssier, D.; Altmann, M.;
Andrae, R.; Audard, M.; Bellas-Velidis, I.; Benson, K.; Berthier,
J.; Blomme, R.; Burgess, P.; Busso, G.; Carry, B.; Cellino, A.;
Clementini, G.; Clotet, M.; Creevey, O.; Davidson, M.; De Ridder, J.;
Delchambre, L.; Dell'Oro, A.; Ducourant, C.; Fernández-Hernández,
J.; Fouesneau, M.; Frémat, Y.; Galluccio, L.; García-Torres,
M.; González-Núñez, J.; González-Vidal, J. J.; Gosset, E.; Guy,
L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison, D. L.; Hernández,
J.; Hestroffer, D.; Hodgkin, S. T.; Hutton, A.; Jasniewicz, G.;
Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.; Krone-Martins, A.;
Lanzafame, A. C.; Lebzelter, T.; Löffler, W.; Manteiga, M.; Marrese,
P. M.; Martín-Fleitas, J. M.; Moitinho, A.; Mora, A.; Muinonen, K.;
Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J. -M.; Recio-Blanco, A.;
Richards, P. J.; Rimoldini, L.; Robin, A. C.; Sarro, L. M.; Siopis,
C.; Smith, M.; Sozzetti, A.; Süveges, M.; Torra, J.; van Reeven, W.;
Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts, C.; Altavilla, G.;
Álvarez, M. A.; Alvarez, R.; Alves, J.; Anderson, R. I.; Andrei,
A. H.; Anglada Varela, E.; Antiche, E.; Antoja, T.; Arcay, B.;
Astraatmadja, T. L.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.;
Balm, P.; Barache, C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem,
P. S.; Barrado, D.; Barros, M.; Barstow, M. A.; Bartholomé Muñoz,
S.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.; Berihuete, A.;
Bertone, S.; Bianchi, L.; Bienaymé, O.; Blanco-Cuaresma, S.; Boch,
T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bossini, D.; Bouquillon,
S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Breddels, M. A.; Bressan,
A.; Brouillet, N.; Brüsemeister, T.; Brugaletta, E.; Bucciarelli,
B.; Burlacu, A.; Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau,
E.; Cancelliere, R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo,
R.; Carlucci, T.; Carrasco, J. M.; Casamiquela, L.; Castellani, M.;
Castro-Ginard, A.; Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza, G.;
Costigan, G.; Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypers,
J.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.;
de Laverny, P.; De Luise, F.; De March, R.; de Martino, D.; de Souza,
R.; de Torres, A.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado,
A.; Delgado, H. E.; Di Matteo, P.; Diakite, S.; Diener, C.; Distefano,
E.; Dolding, C.; Drazinos, P.; Durán, J.; Edvardsson, B.; Enke, H.;
Eriksson, K.; Esquej, P.; Eynard Bontemps, G.; Fabre, C.; Fabrizio,
M.; Faigler, S.; Falcão, A. J.; Farràs Casas, M.; Federici, L.;
Fedorets, G.; Fernique, P.; Figueras, F.; Filippi, F.; Findeisen, K.;
Fonti, A.; Fraile, E.; Fraser, M.; Frézouls, B.; Gai, M.; Galleti, S.;
Garabato, D.; García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel,
A.; Gavras, P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore, G.;
Girona, S.; Giuffrida, G.; Glass, F.; Gomes, M.; Granvik, M.; Gueguen,
A.; Guerrier, A.; Guiraud, J.; Gutiérrez-Sánchez, R.; Haigron, R.;
Hatzidimitriou, D.; Hauser, M.; Haywood, M.; Heiter, U.; Helmi, A.;
Heu, J.; Hilger, T.; Hobbs, D.; Hofmann, W.; Holland, G.; Huckle,
H. E.; Hypki, A.; Icardi, V.; Janßen, K.; Jevardat de Fombelle, G.;
Jonker, P. G.; Juhász, Á. L.; Julbe, F.; Karampelas, A.; Kewley,
A.; Klar, J.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.;
Kontizas, E.; Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.;
Koubsky, P.; Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.;
Le Fustec, Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.;
Leclerc, N.; Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.;
Licata, E.; Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel,
A.; López, M.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.;
Marchant, J. M.; Marconi, M.; Marinoni, S.; Marschalkó, G.; Marshall,
D. J.; Martino, M.; Marton, G.; Mary, N.; Massari, D.; Matijevič,
G.; Mazeh, T.; McMillan, P. J.; Messina, S.; Michalik, D.; Millar,
N. R.; Molina, D.; Molinaro, R.; Molnár, L.; Montegriffo, P.; Mor,
R.; Morbidelli, R.; Morel, T.; Morris, D.; Mulone, A. F.; Muraveva,
T.; Musella, I.; Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane,
W.; Ordénovic, C.; Ordóñez-Blanco, D.; Osborne, P.; Pagani, C.;
Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.; Panahi, A.;
Pawlak, M.; Piersimoni, A. M.; Pineau, F. -X.; Plachy, E.; Plum,
G.; Poggio, E.; Poujoulet, E.; Prša, A.; Pulone, L.; Racero, E.;
Ragaini, S.; Rambaux, N.; Ramos-Lerate, M.; Regibo, S.; Reylé, C.;
Riclet, F.; Ripepi, V.; Riva, A.; Rivard, A.; Rixon, G.; Roegiers,
T.; Roelens, M.; Romero-Gómez, M.; Rowell, N.; Royer, F.; Ruiz-Dern,
L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann, J.; Salgado, J.;
Salguero, E.; Sanna, N.; Santana-Ros, T.; Sarasso, M.; Savietto, H.;
Schultheis, M.; Sciacca, E.; Segol, M.; Segovia, J. C.; Ségransan, D.;
Shih, I. -C.; Siltala, L.; Silva, A. F.; Smart, R. L.; Smith, K. W.;
Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.;
Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmüller, H.;
Stephenson, C. A.; Stoev, H.; Suess, F. F.; Surdej, J.; Szabados, L.;
Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor,
M. B.; Teixeira, R.; Terrett, D.; Teyssandier, P.; Thuillot, W.;
Titarenko, A.; Torra Clotet, F.; Turon, C.; Ulla, A.; Utrilla, E.;
Uzzi, S.; Vaillant, M.; Valentini, G.; Valette, V.; van Elteren,
A.; Van Hemelryck, E.; van Leeuwen, M.; Vaschetto, M.; Vecchiato,
A.; Veljanoski, J.; Viala, Y.; Vicente, D.; Vogt, S.; von Essen, C.;
Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Wertz,
O.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Ziaeepour,
H.; Zorec, J.; Zschocke, S.; Zucker, S.; Zurbach, C.; Zwitter, T.
2018A&A...616A...1G Altcode: 2018arXiv180409365G
Context. We present the second Gaia data release, Gaia DR2, consisting
of astrometry, photometry, radial velocities, and information on
astrophysical parameters and variability, for sources brighter than
magnitude 21. In addition epoch astrometry and photometry are provided
for a modest sample of minor planets in the solar system. <BR />
Aims: A summary of the contents of Gaia DR2 is presented, accompanied
by a discussion on the differences with respect to Gaia DR1 and
an overview of the main limitations which are still present in
the survey. Recommendations are made on the responsible use of
Gaia DR2 results. <BR /> Methods: The raw data collected with the
Gaia instruments during the first 22 months of the mission have
been processed by the Gaia Data Processing and Analysis Consortium
(DPAC) and turned into this second data release, which represents
a major advance with respect to Gaia DR1 in terms of completeness,
performance, and richness of the data products. <BR /> Results: Gaia
DR2 contains celestial positions and the apparent brightness in G for
approximately 1.7 billion sources. For 1.3 billion of those sources,
parallaxes and proper motions are in addition available. The sample
of sources for which variability information is provided is expanded
to 0.5 million stars. This data release contains four new elements:
broad-band colour information in the form of the apparent brightness
in the G<SUB>BP</SUB> (330-680 nm) and G<SUB>RP</SUB> (630-1050 nm)
bands is available for 1.4 billion sources; median radial velocities for
some 7 million sources are presented; for between 77 and 161 million
sources estimates are provided of the stellar effective temperature,
extinction, reddening, and radius and luminosity; and for a pre-selected
list of 14 000 minor planets in the solar system epoch astrometry
and photometry are presented. Finally, Gaia DR2 also represents a
new materialisation of the celestial reference frame in the optical,
the Gaia-CRF2, which is the first optical reference frame based solely
on extragalactic sources. There are notable changes in the photometric
system and the catalogue source list with respect to Gaia DR1, and we
stress the need to consider the two data releases as independent. <BR
/> Conclusions: Gaia DR2 represents a major achievement for the Gaia
mission, delivering on the long standing promise to provide parallaxes
and proper motions for over 1 billion stars, and representing a first
step in the availability of complementary radial velocity and source
astrophysical information for a sample of stars in the Gaia survey
which covers a very substantial fraction of the volume of our galaxy.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Model stellar spectra for B to
early-M (Allende Prieto+, 2018)
Authors: Allende Prieto, C.; Koesterke, L.; Hubeny, I.; Bautista,
M.; Barklem, P. S.; Nahar, S. N.
2018yCat..36180025A Altcode:
The following text describes the data files available from
ftp://carlos:allende@ftp.ll.iac.es/collection <P />These are in ASCII
(but bzip2 compressed), and ready to be used with the FERRE code
(github.com/callendeprieto/ferre). The format includes a header
and as many rows as model spectra. See the FERRE manual for more
details (github.com/callendeprieto/ferre/docs/ferre.pdf). <P />There
are two main families of files. The 'coarse' (nsc) grids consider
three atmospheric parameters ([Fe/H], Teff and logg) and typically
include hundreds of models on a very coarse network, while the
'large' (ns) grids consider five (the previous three plus [alpha/Fe]
and microturbulence), and include tens to hundreds of thousands of
models. <P />The files are numbered 1-5 depending on the Teff range
they span. There are files (ns and nsc) smoothed with a Gaussian
kernal to R=10,000, while nsc files are provided for R=100,000
and 200,000 as well. The spectral range is 0.12-6.6um for the nsc
files and 0.2-2.5um for the ns files. <P />for the nsc files and
0.2-2.5um for the ns files. <P />nsc ('coarse' grids): [Fe/H], Teff,
logg <P />size filename Teff range R <P />158004765 f_nsc1.dat.bz2
3500<= Teff<=6000 10000 128868874 f_nsc2.dat.bz2 5750<=
Teff<=8000 102539424 f_nsc3.dat.bz2 7000<= Teff<=12000 77786534
f_nsc4.dat.bz2 10000<=Teff<=20000 26089034 f_nsc5.dat.bz2
20000<=Teff<=30000 <P />1430284037 f_hnsc1.dat.bz2 3500<=
Teff<=6000 100000 1159906320 f_hnsc2.dat.bz2 5750<= Teff<=8000
913976329 f_hnsc3.dat.bz2 7000<= Teff<=12000 695827559
f_hnsc4.dat.bz2 10000<=Teff<=20000 234598400 f_hnsc5.dat.bz2
20000<=Teff<=30000 <P />2596690648 f_uhnsc1.dat.bz2 3500<=
Teff<=6000 300000 2067630039 f_uhnsc2.dat.bz2 5750<= Teff<=8000
1605227763 f_uhnsc3.dat.bz2 7000<= Teff<=12000 1221970143
f_uhnsc4.dat.bz2 10000<=Teff<=20000 411096450 f_uhnsc5.dat.bz2
20000<=Teff<=30000 <P />ns ('large' grids): [Fe/H], [alpha/Fe],
log(micro), Teff, logg <P />30936708717 f_ns1.dat.bz2 3500<=
Teff<=6000 10000 22957349531 f_ns2.dat.bz2 5750<= Teff<=8000
19640724566 f_ns3.dat.bz2 7000<= Teff<=12000 14267448478
f_ns4.dat.bz2 10000<=Teff<=20000 8622793847 f_ns5.dat.bz2
20000<=Teff<=30000 <P />(2 data files).
---------------------------------------------------------
Title: Effective temperature determinations of late-type stars based
on 3D non-LTE Balmer line formation
Authors: Amarsi, A. M.; Nordlander, T.; Barklem, P. S.; Asplund, M.;
Collet, R.; Lind, K.
2018A&A...615A.139A Altcode: 2018arXiv180402305A
Hydrogen Balmer lines are commonly used as spectroscopic effective
temperature diagnostics of late-type stars. However, reliable
inferences require accurate model spectra, and the absolute accuracy of
classical methods that are based on one-dimensional (1D) hydrostatic
model atmospheres and local thermodynamic equilibrium (LTE) is still
unclear. To investigate this, we carry out 3D non-LTE calculations for
the Balmer lines, performed, for the first time, over an extensive grid
of 3D hydrodynamic STAGGER model atmospheres. For Hα, Hβ, and Hγ we
find significant 1D non-LTE versus 3D non-LTE differences (3D effects):
the outer wings tend to be stronger in 3D models, particularly for
Hγ, while the inner wings can be weaker in 3D models, particularly
for Hα. For Hα, we also find significant 3D LTE versus 3D non-LTE
differences (non-LTE effects): in warmer stars (T<SUB>eff</SUB>
≈ 6500 K) the inner wings tend to be weaker in non-LTE models,
while at lower effective temperatures (T<SUB>eff</SUB> ≈ 4500 K)
the inner wings can be stronger in non-LTE models; the non-LTE effects
are more severe at lower metallicities. We test our 3D non-LTE models
against observations of well-studied benchmark stars. For the Sun,
we infer concordant effective temperatures from Hα, Hβ, and Hγ;
however the value is too low by around 50 K which could signal residual
modelling shortcomings. For other benchmark stars, our 3D non-LTE
models generally reproduce the effective temperatures to within 1σ
uncertainties. For Hα, the absolute 3D effects and non-LTE effects
can separately reach around 100 K, in terms of inferred effective
temperatures. For metal-poor turn-off stars, 1D LTE models of Hα can
underestimate effective temperatures by around 150 K. Our 3D non-LTE
model spectra are publicly available, and can be used for more reliable
spectroscopic effective temperature determinations. <P />The 3D non-LTE
model spectra is also available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/615/A139">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/615/A139</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: 3D non-LTE Balmer line formation
(Amarsi+, 2018)
Authors: Amarsi, A. M.; Nordlander, T.; Barklem, P. S.; Asplund, M.;
Collet, R.; Lind, K.
2018yCat..36150139A Altcode:
File lineprof.txt: contains emergent total (I) and continuum (Ic)
intensities at specific wavelengths (wl, or wl_air) and viewing angles
(mu), the latter with weights (wmu), for the model atmospheres
with different effective temperatures (Teff), surface gravities
(lgg), and iron abundance ratios ([Fe/H]). If rotational broadening
and instrumental broadening are to be neglected, the normalised
flux can be obtained via Sum(I * mu * wmu) / Sum(Ic * mu * wmu),
at a given wavelength and for a given model atmosphere. <P />File
flux_3d.fits: contains a regular grid of normalised fluxes constructed
by interpolation/extrapolation of the data in lineprof.txt. The fluxes
are given for different effective temperatures (Teff), surface gravities
(lgg), iron abundance ratios ([Fe/H]), projected rotational velocity
(vsini), Gaussian instrumental profile velocity widths (vbroad),
vacuum wavelengths (wl), and lines. <P />(2 data files).
---------------------------------------------------------
Title: Excitation and charge transfer in low-energy hydrogen atom
collisions with neutral iron
Authors: Barklem, P. S.
2018A&A...612A..90B Altcode: 2018arXiv180107050B
Data for inelastic processes due to hydrogen atom collisions with iron
are needed for accurate modelling of the iron spectrum in late-type
stars. Excitation and charge transfer in low-energy Fe+H collisions is
studied theoretically using a previously presented method based on an
asymptotic two-electron linear combination of atomic orbitals model of
ionic-covalent interactions in the neutral atom-hydrogen-atom system,
together with the multi-channel Landau-Zener model. An extensive
calculation including 166 covalent states and 25 ionic states is
presented and rate coefficients are calculated for temperatures in
the range 1000-20 000 K. The largest rates are found for charge
transfer processes to and from two clusters of states around 6.3
and 6.6 eV excitation, corresponding in both cases to active 4d
and 5p electrons undergoing transfer. Excitation and de-excitation
processes among these two sets of states are also significant. <P
/>Full Tables and rate coefficient data are only available at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A90">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A90</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: 46 open clusters GaiaDR2 HR
diagrams (Gaia Collaboration, 2018)
Authors: Gaia Collaboration; Babusiaux, C.; van Leeuwen, F.;
Barstow; M., A.; Jordi, C.; Vallenari, A.; Bossini, A.; Bressan,
A.; Cantat-Gaudin, T.; van Leeuwen, M.; Brown, A. G. A.; Prusti,
T.; de Bruijne, J. H. J.; Bailer-Jones, C. A. L.; Biermann, M.;
Evans, D. W.; Eyer, L.; Jansen, F.; Klioner, S. A.; Lammers, U.;
Lindegren, L.; Luri, X.; Mignard, F.; Panem, C.; Pourbaix, D.;
Randich, S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; Walton,
N. A.; Arenou, F.; Bastian, U.; Cropper, M.; Drimmel, R.; Katz, D.;
Lattanzi, M. G.; Bakker, J.; Cacciari, C.; Castaneda, J.; Chaoul,
L.; Cheek, N.; de Angeli, F.; Fabricius, C.; Guerra, R.; Holl, B.;
Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Panuzzo,
P.; Portell, J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thevenin,
F.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Teyssier,
D.; Altmann, M.; Andrae, R.; Audard, M.; Bellas-Velidis, I.; Benson,
K.; Berthier, J.; Blomme, R.; Burgess, P.; Busso, G.; Carry, B.;
Cellino, A.; Clementini, G.; Clotet, M.; Creevey, O.; Davidson,
M.; De Ridder, J.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.;
Fernandez-Hernandez, J.; Fouesneau, M.; Fremat, Y.; Galluccio, L.;
Garcia-Torres, M.; Gonzalez-Nunez, J.; Gonzalez-Vidal, J. J.; Gosset,
E.; Guy, L. P.; Halbwachs, J. -L.; Hambly, N. C.; Harrison, D. L.;
Hernandez, J.; Hestroer, D.; Hodgkin, S. T.; Hutton, A.; Jasniewicz,
G.; Jean-Antoine-Piccolo, A.; Jordan, S.; Korn, A. J.; Krone-Martins,
A.; Lanzafame, A. C.; Lebzelter, T.; Loeer, W.; Manteiga, M.; Marrese,
P. M.; Martin-Fleitas, J. M.; Moitinho, A.; Mora, A.; Muinonen, K.;
Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J. -M.; Recio-Blanco, A.;
Richards, P. J.; Rimoldini, L.; Robin, A. C.; Sarro, L. M.; Siopis,
C.; Smith, M.; Sozzetti, A.; Sueveges, M.; Torra, J.; van Reeven, W.;
Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts, C.; Altavilla, G.;
Alvarez, M. A.; Alvarez, R.; Alves, J.; Anderson, R. I.; Andrei, A. H.;
Anglada Varela, E.; Antiche, E.; Antoja, T.; Arcay, B.; Astraatmadja,
T. L.; Bach, N.; Baker, S. G.; Balaguer-Nunez, L.; Balm, P.; Barache,
C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem, P. S.; Barrado,
D.; Barros, M.; Bartholome Munoz, S.; Bassilana, J. -L.; Becciani, U.;
Bellazzini, M.; Berihuete, A.; Bertone, S.; Bianchi, L.; Bienayme, O.;
Blanco-Cuaresma, S.; Boch, T.; Boeche, C.; Bombrun, A.; Borrachero,
R.; Bouquillon, S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Breddels,
M. A.; Brouillet, N.; Bruesemeister, T.; Brugaletta, E.; Bucciarelli,
B.; Burlacu, A.; Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caau,
E.; Cancelliere, R.; Cannizzaro, G.; Carballo, R.; Carlucci, T.;
Carrasco, J. M.; Casamiquela, L.; Castellani, M.; Castro-Ginard,
A.; Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza, G.; Costigan,
G.; Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.; Cuypersy, J.;
Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; de
Laverny, P.; de Luise, F.; de March, R.; de Martino, D.; de Souza,
R.; de Torres, A.; Debosscher, J.; Del Pozo, E.; Delbo, M.; Delgado,
A.; Delgado, H. E.; Diakite, S.; Diener, C.; Distefano, E.; Dolding,
C.; Drazinos, P.; Duran, J.; Edvardsson, B.; Enke, H.; Eriksson, K.;
Esquej, P.; Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Faigler,
S.; Falcao, A. J.; Farras Casas, M.; Federici, L.; Fedorets, G.;
Fernique, P.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.;
Fraile, E.; Fraser, M.; Frezouls, B.; Gai, M.; Galleti, S.; Garabato,
D.; Garcia-Sedano, F.; Garofalo, A.; Garralda, N.; Gavel, A.; Gavras,
P.; Gerssen, J.; Geyer, R.; Giacobbe, P.; Gilmore, G.; Girona, S.;
Giurida, G.; Glass, F.; Gomes, M.; Granvik, M.; Gueguen, A.; Guerrier,
A.; Guiraud, J.; Gutierrez-Sanchez, R.; Haigron, R.; Hatzidimitriou,
D.; Hauser, M.; Haywood, M.; Heiter, U.; Helmi, A.; Heu, J.; Hilger,
T.; Hobbs, D.; Hofmann, W.; Holland, G.; Huckle, H. E.; Hypki, A.;
Icardi, V.; Janssen, K.; Jevardat de Fombelle, G.; Jonker, P. G.;
Juhasz, A. L.; Julbe, F.; Karampelas, A.; Kewley, A.; Klar, J.;
Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.; Kontizas, E.;
Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.; Koubsky, P.;
Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrom, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; Lopez, M.;
Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant, J. M.;
Marconi, M.; Marinoni, S.; Marschalko, G.; Marshall, D. J.; Martino,
M.; Marton, G.; Mary, N.; Massari, D.; Matijevi?C, G.; Mazeh, T.;
McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Molina,
D.; Molinaro, R.; Molnar, L.; Montegrio, P.; Mor, R.; Morbidelli,
R.; Morel, T.; Morris, D.; Mulone, A. F.; Muraveva, T.; Musella, I.;
Nelemans, G.; Nicastro, L.; Noval, L.; O'Mullane, W.; Ordenovic, C.;
Ordonez-Blanco, D.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.;
Palacin, H.; Palaversa, L.; Panahi, A.; Pawlak, M.; Piersimoni, A. M.;
Pineau, F. -X.; Plachy, E.; Plum, G.; Poggio, E.; Poujoulet, E.; Prsa,
A.; Pulone, L.; Racero, E.; Ragaini, S.; Rambaux, N.; Ramos-Lerate,
M.; Regibo, S.; Reyle, C.; Riclet, F.; Ripepi, V.; Riva, A.; Rivard,
A.; Rixon, G.; Roegiers, T.; Roelens, M.; Romero-Gomez, M.; Rowell,
N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagrista Selles, T.;
Sahlmann, J.; Salgado, J.; Salguero, E.; Sanna, N.; Santana-Ros,
T.; Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol,
M.; Segovia, J. C.; Segransan, D.; Shih, I. -C.; Siltala, L.; Silva,
A. F.; Smart, R. L.; Smith, K. W.; Solano, E.; Solitro, F.; Sordo,
R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa,
U.; Steele, I. A.; Steidelmueller, H.; Stephenson, C. A.; Stoev, H.;
Suess, F. F.; Surdej, J.; Szabados, L.; Szegedi-Elek, E.; Tapiador,
D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett, D.;
Teyssandier, P.; Thuillot, W.; Titarenko, A.; Torra Clotet, F.; Turon,
C.; Ulla, A.; Utrilla, E.; Uzzi, S.; Vaillant, M.; Valentini, G.;
Valette, V.; van Elteren, A.; van Hemelryck, E.; Vaschetto, M.;
Vecchiato, A.; Veljanoski, J.; Viala, Y.; Vicente, D.; Vogt, S.;
von Essen, C.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.;
Weiler, M.; Wertz, O.; Wevers, T.; Wyrzykowski, L.; Yoldas, A.; Zerjal,
M.; Ziaeepour, H.; Zorec, J.; Zschocke, S.; Zucker, S.; Zurbach, C.;
Zwitter, T.
2018yCat..36160010G Altcode:
We have determined the membership of 46 open clusters. For the nine
clusters within 250pc we determined optimised parallaxes based on
the combined information extracted from the measured parallax and
proper motion values. These clusters are : in Tables A1a & A3:
alphaPer, Blanco1, ComaBer, Hyades, IC2391, IC2602, NGC2451A, Pleiades,
Praesepe. The remaining 37 clusters are in Table A1b & A4: Coll140,
IC4651, IC4665, IC4725, IC4756, NGC0188, NGC0752, NGC0869, NGC0884,
NGC1039, NGC1901, NGC2158, NGC2168, NGC2232, NGC2323, NGC2360, NGC2422,
NGC2423, NGC2437, NGC2447, NGC2516, NGC2547, NGC2548, NGC2682, NGC3228,
NGC3532, NGC6025, NGC6281, NGC6405, NGC6475, NGC6633, NGC6774, NGC6793,
NGC7092, Stock2, Trump02, Trump10. <P />(4 data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Gaia DR2 sources in GC and dSph
(Gaia Collaboration+, 2018)
Authors: Gaia Collaboration; Helmi, A.; van Leeuwen, F.; Mc
Millan, P. J.; Massari, D.; Antoja, T.; Robin, A. C.; Lindegren,
L.; Bastian, U.; Arenou, F.; Babusiaux, C.; Biermann, M.; Breddels,
M. A.; Hobbs, D.; Jordi, C.; Pancino, E.; Reyle, C.; Veljanoski, J.;
Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne, J. H. J.;
Bailer-Jones, C. A. L.; Evans, D. W.; Eyer, L.; Jansen, F.; Klioner,
S. A.; Lammers, U.; Luri, X.; Mignard, F.; Panem, C.; Pourbaix, D.;
Randich, S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; Walton,
N. A.; Cropper, M.; Drimmel, R.; Katz, D.; Lattanzi, M. G.; Bakker,
J.; Cacciari, C.; Castaneda, J.; Chaoul, L.; Cheek, N.; de Angeli,
F.; Fabricius, C.; Guerra, R.; Holl, B.; Masana, E.; Messineo, R.;
Mowlavi, N.; Nienartowicz, K.; Panuzzo, P.; Portell, J.; Riello, M.;
Seabroke, G. M.; Tanga, P.; Thevenin, F.; Gracia-Abril, G.; Comoretto,
G.; Garcia-Reinaldos, M.; Teyssier, D.; Altmann, M.; Andrae, R.;
Audard, M.; Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme,
R.; Burgess, P.; Busso, G.; Carry, B.; Cellino, A.; Clementini, G.;
Clotet, M.; ! Creevey, O.; Davidson, M.; De Ridder, J.; Delchambre,
L.; Dell'Oro, A.; Ducourant, C.; Fernandez-Hernandez, J.; Fouesneau,
M.; Fremat, Y.; Galluccio, L.; Garcia-Torres, M.; Gonzalez-Nunez,
J.; Gonzalez-Vidal, J. J.; Gosset, E.; Guy, L. P.; Halbwachs, J. -L.;
Hambly, N. C.; Harrison, D. L.; Hernandez, J.; Hestroffer, D.; Hodgkin,
S. T.; Hutton, A.; Jasniewicz, G.; Jean-Antoine-Piccolo, A.; Jordan,
S.; Korn, A. J.; Krone-Martins, A.; Lanzafame, A. C.; Lebzelter, T.;
Loeffler, W.; Manteiga, M.; Marrese, P. M.; Martin-Fleitas, J. M.;
Moitinho, A.; Mora, A.; Muinonen, K.; Osinde, J.; Pauwels, T.; Petit,
J. -M.; Recio-Blanco, A.; Richards, P. J.; Rimoldini, L.; Sarro,
L. M.; Siopis, C.; Smith, M.; Sozzetti, A.; Sueveges, M.; Torra, J.;
van Reeven, W.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aerts,
C.; Altavilla, G.; Alvarez, M. A.; Alvarez, R.; Alves, J.; Anderson,
R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Arcay, B.;
Astraatmadja, T. L.; Bach, N.; Baker, S. G.; Balaguer-Nunez, L.;
Balm, P.; Barache, C.; Barata, C.; Barbato, D.; Barblan, F.; Barklem,
P. S.; Barra! Do, D.; Ba Rros, M.; Barstow, M. A.; Bartholome Munoz,
S.; Bassilana, J. -L.; Becciani, U.; Bellazzini, M.; Berihuete,
A.; Bertone, S.; Bianchi, L.; Bienayme, O.; Blanco-Cuaresma, S.;
Boch, T.; Boeche, C.; Bombrun, A.; Borrachero, R.; Bossini, D.;
Bouquillon, S.; Bourda, G.; Bragaglia, A.; Bramante, L.; Bressan,
A.; Brouillet, N.; Bruesemeister, T.; Brugaletta, E.; Bucciarelli,
B.; Burlacu, A.; Busonero, D.; Butkevich, A. G.; Buzzi, R.; Caffau,
E.; Cancelliere, R.; Cannizzaro, G.; Cantat-Gaudin, T.; Carballo,
R.; Carlucci, T.; Carrasco, J. M.; Casamiquela, L.; Castellani, M.;
Castro-Ginard, A.; Charlot, P.; Chemin, L.; Chiavassa, A.; Cocozza,
G.; Costigan, G.; Cowell, S.; Crifo, F.; Crosta, M.; Crowley, C.;
Cuypers, J.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.;
David, M.; de Laverny, P.; de Luise, F.; de March, R.; de Martino,
D.; de Souza, R.; de Torres, A.; Debosscher, J.; Del Pozo, E.; Delbo,
M.; Delgado, A.; Delgado, H. E.; Di Matteo, P.; Diakite, S.; Diener,
C.; Distefano, E.; Dolding, C.; Drazinos, P.; Duran, J.; Edvardsson,
B.; Enke, H.; Eriks! Son, K.; E Squej, P.; Eynard Bontemps, G.;
Fabre, C.; Fabrizio, M.; Faigler, S.; Falcao, A. J.; Farras Casas,
M.; Federici, L.; Fedorets, G.; Fernique, P.; Figueras, F.; Filippi,
F.; Findeisen, K.; Fonti, A.; Fraile, E.; Fraser, M.; Frezouls, B.;
Gai, M.; Galleti, S.; Garabato, D.; Garcia-Sedano, F.; Garofalo,
A.; Garralda, N.; Gavel, A.; Gavras, P.; Gerssen, J.; Geyer, R.;
Giacobbe, P.; Gilmore, G.; Girona, S.; Giuffrida, G.; Glass, F.;
Gomes, M.; Granvik, M.; Gueguen, A.; Guerrier, A.; Guiraud, J.;
Gutierrez-Sanchez, R.; Hofmann, W.; Holland, G.; Huckle, H. E.;
Hypki, A.; Icardi, V.; Janssen, K.; Jevardat de Fombelle, G.; Jonker,
P. G.; Juhasz, A. L.; Julbe, F.; Karampelas, A.; Kewley, A.; Klar,
J.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, M.; Kontizas,
E.; Koposov, S. E.; Kordopatis, G.; Kostrzewa-Rutkowska, Z.; Koubsky,
P.; Lambert, S.; Lanza, A. F.; Lasne, Y.; Lavigne, J. -B.; Le Fustec,
Y.; Le Poncin-Lafitte, C.; Lebreton, Y.; Leccia, S.; Leclerc, N.;
Lecoeur-Taibi, I.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.;
Lindstrom, H. E. P.; Lister, T. A.; ! Livanou, E.; Lobel, A.; Lopez,
M.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant,
J. M.; Marconi, M.; Marinoni, S.; Marschalko, G.; Marshall, D. J.;
Martino, M.; Marton, G.; Mary, N.; Matijevic, G.; Mazeh, T.; Messina,
S.; Michalik, D.; Millar, N. R.; Molina, D.; Molinaro, R.; Molnar,
L.; Montegriffo, P.; Mor, R.; Morbidelli, R.; Morel, T.; Morris, D.;
Mulone, A. F.; Muraveva, T.; Musella, I.; Nelemans, G.; Nicastro, L.;
Noval, L.; O'Mullane, W.; Ordenovic, C.; Ordonez-Blanco, D.; Osborne,
P.; Pagani, C.; Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.;
Panahi, A.; Pawlak, M.; Piersimoni, A. M.; Pineau, F. -X.; Plachy, E.;
Plum, G.; Poggio, E.; Poujoulet, E.; Prsa, A.; Pulone, L.; Racero, E.;
Ragaini, S.; Rambaux, N.; Ramos-Lerate, M.; Regibo, S.; Riclet, F.;
Ripepi, V.; Riva, A.; Rivard, A.; Rixon, G.; Roegiers, T.; Roelens,
M.; Romero-Gomez, M.; Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski,
G.; Sagrista Selles, T.; Sahlmann, J.; Salgado, J.; Salguero, E.;
Sanna, N.; Santana-Ros, T.; Sarasso, M.; Savietto, H.; Schultheis,
M.; Sciacca, E.; Segol !, M.; Segov, Ia J. C.; Segransan, D.; Shih,
I. -C.; Siltala, L.; Silva, A. F.; Smart, R. L.; Smith, K. W.;
Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.;
Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmueller, H.;
Stephenson, C. A.; Stoev, H.; Suess, F. F.; Surdej, J.; Szabados, L.;
Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor, M. B.;
Teixeira, R.; Terrett, D.; Teyssandier, P.; Thuillot, W.; Titarenko,
A.; Torra Clotet, F.; Turon, C.; Ulla, A.; Utrilla, E.; Uzzi,
S.; Vaillant, M.; Valentini, G.; Valette, V.; van Elteren, A.;
van Hemelryck, E.; van Leeuwen, M.; Vaschetto, M.; Vecchiato, A.;
Viala, Y.; Vicente, D.; Vogt, S.; von Essen, C.; Voss, H.; Votruba,
V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Wertz, O.; Wevems, T.;
Wyrzykowski, L.; Yoldas, A.; Zerjal, M.; Ziaeepour, H.; Zorec, J.;
Zschocke, S.; Zucker, S.; Zurbach, C.; Zwitter, T.
2018yCat..36160012G Altcode:
The files contains lists of possible members of each of the objects
(75 globular clusters, 9 dwarf spheroidal galaxies, the Bootes I UFD,
the LMC and SMC). The stars in these lists have been selected and used
to determine the astrometric parameters of the corresponding objects
following either the procedures described in Sec. 2.1 (for the clusters
and dwarfs) or in Sec. 2.2 (for the LMC and SMC). The first column is
the "source_id" as given by Gaia, the ra and declination of the star in
degrees, and its G-band magnitude (known as "phot<SUB>g</SUB>mean_mag"
in the Gaia archive). <P />(2 data files).
---------------------------------------------------------
Title: A New Test of Copper and Zinc Abundances in Late-type Stars
Using Ultraviolet Cu II and Zn II Lines
Authors: Roederer, Ian U.; Barklem, Paul S.
2018ApJ...857....2R Altcode: 2018arXiv180309763R
We present new abundances derived from Cu I, Cu II, Zn I, and Zn II
lines in six warm (5766 ≤ {T}<SUB>eff</SUB>} ≤ 6427 K), metal-poor
(-2.50 ≤ [Fe/H] ≤ -0.95) dwarf and subgiant (3.64 ≤ log g ≤
4.44) stars. These abundances are derived from archival high-resolution
ultraviolet spectra from the Space Telescope Imaging Spectrograph on
board the Hubble Space Telescope and ground-based optical spectra from
several observatories. Ionized Cu and Zn are the majority species,
and abundances derived from Cu II and Zn II lines should be largely
insensitive to departures from local thermodynamic equilibrium
(LTE). We find good agreement between the [Zn/H] ratios derived
separately from Zn I and Zn II lines, suggesting that departures
from LTE are, at most, minimal (≲0.1 dex). We find that the [Cu/H]
ratios derived from Cu II lines are 0.36 ± 0.06 dex larger than those
derived from Cu I lines in the most metal-poor stars ([Fe/H] < -1.8),
suggesting that LTE underestimates the Cu abundance derived from Cu I
lines. The deviations decrease in more metal-rich stars. Our results
validate previous theoretical non-LTE calculations for both Cu and
Zn, supporting earlier conclusions that the enhancement of [Zn/Fe]
in metal-poor stars is legitimate, and the deficiency of [Cu/Fe] in
metal-poor stars may not be as large as previously thought. <P />Based
on observations made with the NASA/ESA Hubble Space Telescope, obtained
from the data archive at the Space Telescope Science Institute (STScI),
which is operated by the Association of Universities for Research in
Astronomy, Inc. (AURA) under NASA contract NAS 5-26555. This work is
supported by NASA through grant number AR-15051 and makes use of data
from programs GO-7348, GO-8197, GO-9804, GO-14161, and GO-14672. This
research has also made use of the Keck Observatory Archive (KOA),
which is operated by the W.M. Keck Observatory and the NASA Exoplanet
Science Institute (NExScI), under contract with NASA. These data are
associated with programs C314Hr, H6aH, and H283Hr. Other data have
been obtained from the European Southern Observatory (ESO) Science
Archive Facility. These data are associated with programs 65.L-0507(A),
67.D-0439(A), and 080.D-0347(A). This work has also made use of data
collected from the McDonald Observatory of the University of Texas
at Austin.
---------------------------------------------------------
Title: Excitation and charge transfer in low-energy hydrogen atom
collisions with neutral oxygen
Authors: Barklem, P. S.
2018A&A...610A..57B Altcode: 2017arXiv171201166B
Excitation and charge transfer in low-energy O+H collisions is studied;
it is a problem of importance for modelling stellar spectra and
obtaining accurate oxygen abundances in late-type stars including
the Sun. The collisions have been studied theoretically using a
previously presented method based on an asymptotic two-electron
linear combination of atomic orbitals (LCAO) model of ionic-covalent
interactions in the neutral atom-hydrogen-atom system, together
with the multichannel Landau-Zener model. The method has been
extended to include configurations involving excited states of
hydrogen using an estimate for the two-electron transition coupling,
but this extension was found to not lead to any remarkably high
rates. Rate coefficients are calculated for temperatures in the
range 1000-20 000 K, and charge transfer and (de)excitation processes
involving the first excited S-states, 4s.<SUP>5</SUP>S<SUP>o</SUP>
and 4s.<SUP>3</SUP>S<SUP>o</SUP>, are found to have the highest
rates. <P />Data are available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://cdsarc.u-strasbg.fr">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57">http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57</A>.
The data are also available at <A
href="https://github.com/barklem/public-data">https://github.com/barklem/public-data</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Inelastic Fe+H collision data
(Barklem, 2018)
Authors: Barklem, P. S.
2018yCat..36120090B Altcode:
The file states.dat lists the considered states. The remaining files
then provide the rate coefficients and "fluctuations". <P />(3 data
files).
---------------------------------------------------------
Title: Data on inelastic processes in low-energy potassium-hydrogen
and rubidium-hydrogen collisions
Authors: Yakovleva, S. A.; Barklem, P. S.; Belyaev, A. K.
2018MNRAS.473.3810Y Altcode:
Two sets of rate coefficients for low-energy inelastic
potassium-hydrogen and rubidium-hydrogen collisions were computed
for each collisional system based on two model electronic structure
calculations, performed by the quantum asymptotic semi-empirical and
the quantum asymptotic linear combinations of atomic orbitals (LCAO)
approaches, followed by quantum multichannel calculations for the
non-adiabatic nuclear dynamics. The rate coefficients for the charge
transfer (mutual neutralization, ion-pair formation), excitation
and de-excitation processes are calculated for all transitions
between the five lowest lying covalent states and the ionic states
for each collisional system for the temperature range 1000-10 000
K. The processes involving higher lying states have extremely low rate
coefficients and, hence, are neglected. The two model calculations both
single out the same partial processes as having large and moderate
rate coefficients. The largest rate coefficients correspond to the
mutual neutralization processes into the K(5s <SUP>2</SUP>S) and Rb(4d
<SUP>2</SUP>D) final states and at temperature 6000 K have values
exceeding 3 × 10<SUP>-8</SUP> cm<SUP>3</SUP> s<SUP>-1</SUP> and 4 ×
10<SUP>-8</SUP> cm<SUP>3</SUP> s<SUP>-1</SUP>, respectively. It is shown
that both the semi-empirical and the LCAO approaches perform equally
well on average and that both sets of atomic data have roughly the
same accuracy. The processes with large and moderate rate coefficients
are likely to be important for non-LTE modelling in atmospheres of F,
G and K-stars, especially metal-poor stars.
---------------------------------------------------------
Title: The Hamburg/ESO R-process Enhanced Star survey (HERES). XI. The
highly r-process-enhanced star CS 29497-004
Authors: Hill, V.; Christlieb, N.; Beers, T. C.; Barklem, P. S.;
Kratz, K. -L.; Nordström, B.; Pfeiffer, B.; Farouqi, K.
2017A&A...607A..91H Altcode: 2016arXiv160807463H
We report an abundance analysis for the highly r-process-enhanced (r-II)
star <ASTROBJ>CS 29497-004</ASTROBJ>, a very metal-poor giant with solar
system T<SUB>eff</SUB> = 5013 K and [Fe/H] = -2.85, whose nature was
initially discovered in the course of the HERES project. Our analysis
is based on high signal-to-noise ratio, high-resolution (R 75 000)
VLT/UVES spectra and MARCS model atmospheres under the assumption of
local thermodynamic equilibrium, and obtains abundance measurements for
a total of 46 elements, 31 of which are neutron-capture elements. As is
the case for the other 25 r-II stars currently known, the heavy-element
abundance pattern of <ASTROBJ>CS 29497-004</ASTROBJ> well-matches a
scaled solar system second peak r-process-element abundance pattern. We
confirm our previous detection of Th, and demonstrate that this
star does not exhibit an "actinide boost". Uranium is also detected
(log ɛ(U) = -2.20 ± 0.30), albeit with a large measurement error
that hampers its use as a precision cosmo-chronometer. Combining the
various elemental chronometer pairs that are available for this star,
we derive a mean age of 12.2 ± 3.7 Gyr using the theoretical production
ratios from published waiting-point approximation models. We further
explore the high-entropy wind model (Farouqi et al. 2010, ApJ, 712,
1359) production ratios arising from different neutron richness of
the ejecta (Y<SUB>e</SUB>), and derive an age of 13.7 ± 4.4 Gyr for
a best-fitting Y<SUB>e</SUB> = 0.447. The U/Th nuclei-chronometer is
confirmed to be the most resilient to theoretical production ratios
and yields an age of 16.5 ± 6.6 Gyr. Lead (Pb) is also tentatively
detected in <ASTROBJ>CS 29497-004</ASTROBJ>, at a level compatible with
a scaled solar r-process, or with the theoretical expectations for a
pure r-process in this star. <P />Based on observations collected at
the European Southern Observatory, Paranal, Chile (Proposal Number
170.D-0010).Table B.1 is only available at the CDS via anonymous ftp
to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A91">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A91</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: CS 29497-004 abundances (Hill+,
2017)
Authors: Hill, V.; Christlieb, N.; Beers, T. C.; Barklem, P. S.;
Kratz, K. -L.; Nordstrom, B.; Pfeiffer, B.; Farouqi, K.
2017yCat..36070091H Altcode:
High-resolution spectra of CS 29497-004 were obtained with UVES at
VLT-UT2 during October-December 2002 and July-August 2003. A total of
22 exposures were obtained with the BLUE346 setting, and six with the
BLUE437 setting. In both cases Image Slicer #2 was used, yielding a
nominal resolving power of R=λ/Δλ=75000. The total useful wavelength
range covered by these two settings is 3050-4980Å in the rest frame
of the star. <P />(1 data file).
---------------------------------------------------------
Title: Inelastic e+Mg collision data and its impact on modelling
stellar and supernova spectra
Authors: Barklem, P. S.; Osorio, Y.; Fursa, D. V.; Bray, I.;
Zatsarinny, O.; Bartschat, K.; Jerkstrand, A.
2017A&A...606A..11B Altcode: 2017arXiv170603399B
Results of calculations for inelastic e+Mg effective collision strengths
for the lowest 25 physical states of Mg I (up to 3s6p<SUP>1</SUP>P),
and thus 300 transitions, from the convergent close-coupling (CCC) and
the B-spline R-matrix (BSR) methods are presented. At temperatures
of interest, 5000 K, the results of the two calculations differ
on average by only 4%, with a scatter of 27%. As the methods are
independent, this suggests that the calculations provide datasets
for e+Mg collisions accurate to this level. Comparison with the
commonly used dataset compiled by Mauas et al. (1988, ApJ, 330,
1008), covering 25 transitions among 12 states, suggests the Mauas et
al. data are on average 57% too low, and with a very large scatter
of a factor of 6.5. In particular the collision strength for the
transition corresponding to the Mg I intercombination line at 457 nm
is significantly underestimated by Mauas et al., which has consequences
for models that employ this dataset. In giant stars the new data leads
to a stronger line compared to previous non-LTE calculations, and thus
a reduction in the non-LTE abundance correction by 0.1 dex ( 25%). A
non-LTE calculation in a supernova ejecta model shows this line becomes
significantly stronger, by a factor of around two, alleviating the
discrepancy where the 457 nm line in typical models with Mg/O ratios
close to solar tended to be too weak compared to observations. <P
/>Full Tables 2 and 3 are only available at the CDS via anonymous ftp
to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A11">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A11</A>
---------------------------------------------------------
Title: Non-LTE line formation of Fe in late-type stars - IV. Modelling
of the solar centre-to-limb variation in 3D
Authors: Lind, K.; Amarsi, A. M.; Asplund, M.; Barklem, P. S.;
Bautista, M.; Bergemann, M.; Collet, R.; Kiselman, D.; Leenaarts,
J.; Pereira, T. M. D.
2017MNRAS.468.4311L Altcode: 2017arXiv170304027L
Our ability to model the shapes and strengths of iron lines in the solar
spectrum is a critical test of the accuracy of the solar iron abundance,
which sets the absolute zero-point of all stellar metallicities. We use
an extensive 463-level Fe atom with new photoionization cross-sections
for Fe I and quantum mechanical calculations of collisional excitation
and charge transfer with neutral hydrogen; the latter effectively remove
a free parameter that has hampered all previous line formation studies
of Fe in non-local thermodynamic equilibrium (NLTE). For the first
time, we use realistic 3D NLTE calculations of Fe for a quantitative
comparison to solar observations. We confront our theoretical line
profiles with observations taken at different viewing angles across
the solar disc with the Swedish 1-m Solar Telescope. We find that
3D modelling well reproduces the observed centre-to-limb behaviour
of spectral lines overall, but highlight aspects that may require
further work, especially cross-sections for inelastic collisions with
electrons. Our inferred solar iron abundance is log (ɛ<SUB>Fe</SUB>)
= 7.48 ± 0.04 dex.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Inelastic e+Mg collision data
(Barklem+, 2017)
Authors: Barklem, P. S.; Osorio, Y.; Fursa, D. V.; Bray, I.;
Zatsarinny, O.; Bartschat, K.; Jerkstrand, A.
2017yCat..36060011B Altcode:
The file states.dat lists the considered states. The remaining files
then provide the effective collision strength matrices for various
temperatures from the convergent close coupling (CCC) and B-spline
R-matrix (BSR) calculations. <P />(27 data files).
---------------------------------------------------------
Title: MSWAVEF: Momentum-Space Wavefunctions
Authors: Barklem, Paul S.
2017ascl.soft01006B Altcode:
MSWAVEF calculates hydrogenic and non-hydrogenic momentum-space
electronic wavefunctions. Such wavefunctions are often required to
calculate various collision processes, such as excitation and line
broadening cross sections. The hydrogenic functions are calculated using
the standard analytical expressions. The non-hydrogenic functions are
calculated within quantum defect theory according to the method of Hoang
Binh and van Regemorter (1997). Required Hankel transforms have been
determined analytically for angular momentum quantum numbers ranging
from zero to 13 using Mathematica. Calculations for higher angular
momentum quantum numbers are possible, but slow (since calculated
numerically). The code is written in IDL.
---------------------------------------------------------
Title: KAULAKYS: Inelastic collisions between hydrogen atoms and
Rydberg atoms
Authors: Barklem, Paul S.
2017ascl.soft01005B Altcode:
KAULAKYS calculates cross sections and rate coefficients for inelastic
collisions between Rydberg atoms and hydrogen atoms according to the
free electron model of Kaulakys (1986, 1991). It is written in IDL and
requires the code MSWAVEF (ascl:1701.006) to calculate momentum-space
wavefunctions. KAULAKYS can be easily adapted to collisions with
perturbers other than hydrogen atoms by providing the appropriate
scattering amplitudes.
---------------------------------------------------------
Title: Excitation and charge transfer in low-energy hydrogen atom
collisions with neutral oxygen.
Authors: Barklem, P. S.
2017yCat..36100057B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: 3D NLTE analysis of the most iron-deficient star, SMSS0313-6708
Authors: Nordlander, T.; Amarsi, A. M.; Lind, K.; Asplund, M.; Barklem,
P. S.; Casey, A. R.; Collet, R.; Leenaarts, J.
2017A&A...597A...6N Altcode: 2016arXiv160907416N; 2016A&A...597A...6N
Context. Models of star formation in the early universe require
a detailed understanding of accretion, fragmentation and radiative
feedback in metal-free molecular clouds. Different simulations predict
different initial mass functions of the first stars, ranging from
predominantly low-mass (0.1-10 M<SUB>⊙</SUB>), to massive (10-100
M<SUB>⊙</SUB>), or even supermassive (100-1000 M<SUB>⊙</SUB>). The
mass distribution of the first stars should lead to unique chemical
imprints on the low-mass second and later generation metal-poor
stars still in existence. The chemical composition of SMSS0313-6708,
which has the lowest abundances of Ca and Fe of any star known,
indicates it was enriched by a single massive supernova. <BR /> Aims:
The photospheres of metal-poor stars are relatively transparent in
the UV, which may lead to large three-dimensional (3D) effects as
well as departures from local thermodynamical equilibrium (LTE),
even for weak spectral lines. If 3D effects and departures from LTE
(NLTE) are ignored or treated incorrectly, errors in the inferred
abundances may significantly bias the inferred properties of the
polluting supernovae. We redetermine the chemical composition of
SMSS0313-6708by means of the most realistic methods available, and
compare the results to predicted supernova yields. <BR /> Methods:
A 3D hydrodynamical Staggermodel atmosphere and 3D NLTE radiative
transfer were applied to obtain accurate abundances for Li, Na, Mg, Al,
Ca and Fe. The model atoms employ realistic collisional rates, with
no calibrated free parameters. <BR /> Results: We find significantly
higher abundances in 3D NLTE than 1D LTE by 0.8 dex for Fe, and 0.5
dex for Mg, Al and Ca, while Li and Na are unaffected to within 0.03
dex. In particular, our upper limit for [Fe/H] is now a factor ten
larger, at [Fe/H] < -6.53 (3σ), than previous estimates based on
⟨ 3D ⟩NLTE (I.e., using averaged 3D models). This higher estimate
is due to a conservative upper limit estimation, updated NLTE data,
and 3D-⟨ 3D ⟩NLTE differences, all of which lead to a higher
abundance determination. <BR /> Conclusions: We find that supernova
yields for models in a wide range of progenitor masses reproduce the
revised chemical composition. In addition to massive progenitors of
20-60 M<SUB>⊙</SUB> exploding with low energies (1-2 B, where 1
B = 10<SUP>51</SUP> erg), we also find good fits for progenitors of
10 M<SUB>⊙</SUB>, with very low explosion energies (<1 B). We
cannot reconcile the new abundances with supernovae or hypernovae with
explosion energies above 2.5 B, nor with pair-instability supernovae.
---------------------------------------------------------
Title: Non-LTE line formation of Fe in late-type stars - III. 3D
non-LTE analysis of metal-poor stars
Authors: Amarsi, A. M.; Lind, K.; Asplund, M.; Barklem, P. S.;
Collet, R.
2016MNRAS.463.1518A Altcode: 2016arXiv160806390A; 2016MNRAS.tmp.1203A
As one of the most important elements in astronomy, iron abundance
determinations need to be as accurate as possible. We investigate the
accuracy of spectroscopic iron abundance analyses using archetypal
metal-poor stars. We perform detailed 3D non-LTE radiative transfer
calculations based on 3D hydrodynamic STAGGER model atmospheres, and
employ a new model atom that includes new quantum-mechanical neutral
hydrogen collisional rate coefficients. With the exception of the
red giant HD122563, we find that the 3D non-LTE models achieve Fe
I/Fe II excitation and ionization balance as well as not having any
trends with equivalent width to within modelling uncertainties of
0.05 dex, all without having to invoke any microturbulent broadening;
for HD122563 we predict that the current best parallax-based surface
gravity is overestimated by 0.5 dex. Using a 3D non-LTE analysis, we
infer iron abundances from the 3D model atmospheres that are roughly
0.1 dex higher than corresponding abundances from 1D MARCS model
atmospheres; these differences go in the same direction as the non-LTE
effects themselves. We make available grids of departure coefficients,
equivalent widths and abundance corrections, calculated on 1D MARCS
model atmospheres and horizontally and temporally averaged 3D STAGGER
model atmospheres.
---------------------------------------------------------
Title: Accurate abundance analysis of late-type stars: advances in
atomic physics
Authors: Barklem, Paul S.
2016A&ARv..24....9B Altcode: 2016arXiv160407659B
The measurement of stellar properties such as chemical compositions,
masses and ages, through stellar spectra, is a fundamental problem
in astrophysics. Progress in the understanding, calculation and
measurement of atomic properties and processes relevant to the
high-accuracy analysis of F-, G-, and K-type stellar spectra is
reviewed, with particular emphasis on abundance analysis. This
includes fundamental atomic data such as energy levels, wavelengths,
and transition probabilities, as well as processes of photoionisation,
collisional broadening and inelastic collisions. A recurring theme
throughout the review is the interplay between theoretical atomic
physics, laboratory measurements, and astrophysical modelling, all of
which contribute to our understanding of atoms and atomic processes,
as well as to modelling stellar spectra.
---------------------------------------------------------
Title: Mswavef: April 2016 Release
Authors: Barklem, Paul
2016zndo.....50218B Altcode:
First formal github release
---------------------------------------------------------
Title: Abo-Cross: April 2016 Release
Authors: Barklem, Paul
2016zndo.....50216B Altcode:
First formal github release
---------------------------------------------------------
Title: Kaulakys: April 2016 Release
Authors: Barklem, Paul
2016zndo.....50217B Altcode:
First formal github release
---------------------------------------------------------
Title: Hlinop: April 2016 Release
Authors: Barklem, Paul; Piskunov, Nikolai
2016zndo.....50215B Altcode:
First formal github release. April 2016 version.
---------------------------------------------------------
Title: Excitation and charge transfer in low-energy hydrogen-atom
collisions with neutral atoms: Theory, comparisons, and application
to Ca
Authors: Barklem, Paul S.
2016PhRvA..93d2705B Altcode: 2016arXiv160307097B
A theoretical method is presented for the estimation of cross
sections and rates for excitation and charge-transfer processes in
low-energy hydrogen-atom collisions with neutral atoms, based on an
asymptotic two-electron model of ionic-covalent interactions in the
neutral atom-hydrogen-atom system. The calculation of potentials and
nonadiabatic radial couplings using the method is demonstrated. The
potentials are used together with the multichannel Landau-Zener model to
calculate cross sections and rate coefficients. The main feature of the
method is that it employs asymptotically exact atomic wave functions,
which can be determined from known atomic parameters. The method is
applied to Li+H , Na+H , and Mg+H collisions, and the results compare
well with existing detailed full-quantum calculations. The method is
applied to the astrophysically important problem of Ca+H collisions,
and rate coefficients are calculated for temperatures in the range
1000-20 000 K.
---------------------------------------------------------
Title: Division B Commission 14: Atomic and Molecular Data
Authors: Mashonkina, Lyudmila I.; Salama, Farid; Wahlgren, Glenn M.;
Allard, France; Barklem, Paul; Beiersdorfer, Peter; Fraser, Helen;
Nave, Gillian; Nilsson, Hampus
2016IAUTA..29...99M Altcode:
The main purpose of Commission 14 is to foster interactions between
the astronomical community and those conducting research on atoms,
molecules, and solid state particles to provide data vital to reducing
and analysing astronomical observations and performing theoretical
investigations.
---------------------------------------------------------
Title: Division B Commission 14 Working Group: Collision Processes
Authors: Peach, Gillian; Dimitrijevic, Milan S.; Barklem, Paul S.
2016IAUTA..29..120P Altcode:
Since our last report (Peach & Dimitrijević 2012), a large
number of new publications on the results of research in atomic and
molecular collision processes and spectral line broadening have been
published. Due to the limited space available, we have only included
work of importance for astrophysics. Additional relevant papers,
not included in this report, can be found in the databases at the
web addresses provided in Section 6. Elastic and inelastic collisions
between electrons, atoms, ions, and molecules are included, as well
as charge transfer in collisions between heavy particles which can be
very important.
---------------------------------------------------------
Title: Partition functions and equilibrium constants for diatomic
molecules and atoms of astrophysical interest
Authors: Barklem, P. S.; Collet, R.
2016A&A...588A..96B Altcode: 2016arXiv160203304B
Partition functions and dissociation equilibrium constants are presented
for 291 diatomic molecules for temperatures in the range from near
absolute zero to 10 000 K, thus providing data for many diatomic
molecules of astrophysical interest at low temperature. The calculations
are based on molecular spectroscopic data from the book of Huber &
Herzberg (1979, Constants of Diatomic Molecules) with significant
improvements from the literature, especially updated data for ground
states of many of the most important molecules by Irikura (2007,
J. Phys. Chem. Ref. Data, 36, 389). Dissociation energies are collated
from compilations of experimental and theoretical values. Partition
functions for 284 species of atoms for all elements from H to U are
also presented based on data collected at NIST. The calculated data are
expected to be useful for modelling a range of low density astrophysical
environments, especially star-forming regions, protoplanetary disks,
the interstellar medium, and planetary and cool stellar atmospheres. The
input data, which will be made available electronically, also provides a
possible foundation for future improvement by the community. <P />Full
Tables 1-8 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A96">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A96</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Partition functions for molecules
and atoms (Barklem+, 2016)
Authors: Barklem, P. S.; Collet, R.
2016yCat..35880096B Altcode:
The results and input data are presented in the following files. <P
/>Table 1 contains dissociation energies from the literature, and
final adopted values, for 291 molecules. The literature values are from
the compilations of Huber & Herzberg (1979, Constants of Diatomic
Molecules (Van Nostrand Reinhold), Luo (2007, Comprehensive Handbook
of Chemical Bond Energies (CRC Press)) and G2 theory calculations of
Curtiss et al. (1991, J. Chem. Phys., 94, 7221). <P />Table 2 contains
the input data for the molecular calculations including adopted
dissociation energy, nuclear spins, molecular spectroscopic constants
and their sources. There are 291 files, one for each molecule, labelled
by the molecule name. The various molecular spectroscopic constants are
as defined in the paper. <P />Table 4 contains the first, second and
third ionisation energies for all chemical elements from H to U. The
data comes from the CRC Handbook of Chemistry and Physics (Haynes,
W.M. 2010, CRC Handbook of Chemistry and Physics, 91st edn. (CRC Press,
Taylor and Francis Group)). <P />Table 5a contains a list of keys to
bibliographic references for the atomic energy level data that was
extracted from NIST Atomic Spectra Database and used in the present
work to compute atomic partition functions. The citation keys are
abbreviations of the full bibliographic references which are made
available in Table 5b in BibTeX format. <P />Table 5b contains the
full bibliographic references for the atomic energy level data that was
extracted from the NIST Atomic Spectra Database. <P />Table 6 contains
tabulated partition function data as a function of temperature for 291
molecules. <P />Table 7 contains tabulated equilibrium constant data
as a function of temperature for 291 molecules. <P />Table 8 contains
tabulated partition function data as a function of temperature for
284 atoms and ions. <P />The paper should be consulted for further
details. <P />(10 data files).
---------------------------------------------------------
Title: Mg line formation in late-type stellar
atmospheres. II. Calculations in a grid of 1D models
Authors: Osorio, Y.; Barklem, P. S.
2016A&A...586A.120O Altcode: 2015arXiv151005165O
Context. Mg is the α element of choice for Galactic population and
chemical evolution studies because it is easily detectable in all
late-type stars. Such studies require precise elemental abundances, and
thus departures from local thermodynamic equilibrium (LTE) need to be
accounted for. <BR /> Aims: Our goal is to provide reliable departure
coefficients and equivalent widths in non-LTE, and for reference in
LTE, for diagnostic lines of Mg studied in late-type stars. These can
be used, for example, to correct LTE spectra and abundances. <BR />
Methods: Using the model atom built and tested in the preceding paper
in this series, we performed non-LTE radiative transfer calculations
in a grid of 3945 stellar 1D atmospheric models. We used a sub-grid of
86 models to explore the propagation of errors in the recent atomic
collision calculations to the radiative transfer results. <BR />
Results: We obtained departure coefficients for all the levels and
equivalent widths (in LTE and non-LTE) for all the radiative transitions
included in the "final" model atom presented in Paper I. Here we present
and describe our results and show some examples of applications of the
data. The errors that result from uncertainties in the collisional
data are investigated and tabulated. The results for equivalent
widths and departure coefficients are made freely available. <BR />
Conclusions: Giants tend to have negative abundance corrections while
dwarfs have positive, though small, corrections. Error analysis
results show that uncertainties related to the atomic collision
data are typically on the order of 0.01 dex or less, although for
few stellar models in specific lines uncertainties can be as large
as 0.03 dex. As these errors are less than or on the same order
as typical corrections, we expect that we can use these results to
extract Mg abundances from high-quality spectra more reliably than
from classical LTE analysis. <P />Full Table 1 is only available at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/586/A120">http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/586/A120</A>
<P /><P />http://The same data is accessible via the INSPECT project <A
href="http://inspect.coolstars19.com">http://inspect.coolstars19.com</A>
---------------------------------------------------------
Title: Unified numerical model of collisional depolarization and
broadening rates that are due to hydrogen atom collisions
Authors: Derouich, M.; Radi, A.; Barklem, P. S.
2015A&A...584A..64D Altcode: 2015arXiv150806482D
Context. Accounting for partial or complete frequency redistribution
when interpreting solar polarization spectra requires data on various
collisional processes. Data for depolarization and polarization transfer
are needed, but are often lacking, while data for collisional broadening
are usually more readily available. Recently it was concluded that
despite underlying similarities in the physics of collisional broadening
and depolarization processes, the relations between them cannot be
derived purely analytically. <BR /> Aims: We aim to derive accurate
numerical relations between the collisional broadening rates and the
collisional depolarization and polarization transfer rates that are due
to hydrogen atom collisions. These relations would enable accurate and
efficient estimates of collisional data for solar applications. <BR
/> Methods: Using earlier results for broadening and depolarization
processes based on general (i.e., not specific to a given atom),
semi-classical calculations that employ interaction potentials
from perturbation theory, we used genetic programming (GP) to fit
the available data and generate analytical functions describing the
relations between them. The predicted relations from the GP-based model
were compared with the original data to estimate the accuracy of the
method. <BR /> Results: We obtain strongly nonlinear relations between
the collisional broadening rates and the depolarization and polarization
transfer rates. They are shown to reproduce the original data with an
accuracy of about 5%. Our results allow determining the depolarization
and polarization transfer rates for hyperfine or fine-structure levels
of simple and complex atoms. <BR /> Conclusions: We show that by using
a sophisticated numerical approach and a general collision theory,
useful relations with sufficient accuracy for applications are possible.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Grid of 1D models for Mg line
formation (Osorio+, 2016)
Authors: Osorio, Y.; Barklem, P. S.
2015yCat..35860120O Altcode:
Table mgnlte.dat provides equivalent widths in LTE and non-LTE for
19 MgI spectral lines calculated in 3859 stellar atmospheres and
using 21 Mg abundance per star. These data can be used to calculate
abundance corrections in a broad variety of stellar models and Mg
enhancements in a consistent way. <P />The tables in data/* provides
departure coefficients of the LEVEL in 10563 stellar atmospheres at 56
depth points in the atmosphere and using 21 Mg abundance values per
star. These data can be used to calculate abundance corrections in a
broad variety of stellar models and Mg enhancements in a consistent
way. <P />The format of the departure coefficients is the unit-less
value of the ratio between the nlte and lte population of the level
LEVEL of Mg. <P />(3 data files).
---------------------------------------------------------
Title: Division XII: Commission 14: Atomic and Molecular Data
Authors: Mashonkina, Lyudmila I.; Salama, Farid; Wahlgren, Glenn M.;
Allard, France; Barklem, Paul; Beiersdorfer, Peter; Fraser, Helen;
Nave, Gillian; Nilsson, Hampus
2015IAUTB..28..135M Altcode:
The meeting was called to order by the Chair, who followed the agenda
that had been sent to the membership prior to the meeting. The
membership of the Commission stands at approximately 220 members,
excluding the new members who will join the commission at the end of
this General Assembly.
---------------------------------------------------------
Title: HLINOP: Hydrogen LINe OPacity in stellar atmospheres
Authors: Barklem, P. S.; Piskunov, N.
2015ascl.soft07008B Altcode:
HLINOP is a collection of codes for computing hydrogen line profiles
and opacities in the conditions typical of stellar atmospheres. It
includes HLINOP for approximate quick calculation of any line of
neutral hydrogen (suitable for model atmosphere calculations),
based on the Fortran code of Kurucz and Peterson found in <A
href="http://kurucz.harvard.edu/programs/atlas9/atlas9xlinop.for">ATLAS9</A>.
It also includes HLINPROF, for detailed, accurate calculation of lower
Balmer line profiles (suitable for detailed analysis of Balmer lines)
and HBOP, to implement the occupation probability formalism of Daeppen,
Anderson and Milhalas (1987) and thus account for the merging of
bound-bound and bound-free opacity (used often as a wrapper to HLINOP
for model atmosphere calculations).
---------------------------------------------------------
Title: abo-cross: Hydrogen broadening cross-section calculator
Authors: Barklem, P. S.; Anstee, S. D.; O'Mara, B. J.
2015ascl.soft07007B Altcode:
Line broadening cross sections for the broadening of spectral lines by
collisions with neutral hydrogen atoms have been tabulated by Anstee
& O'Mara (1995), Barklem & O'Mara (1997) and Barklem, O'Mara
& Ross (1998) for s–p, p–s, p–d, d–p, d–f and f–d
transitions. abo-cross, written in Fortran, interpolates in these
tabulations to make these data more accessible to the end user. This
code can be incorporated into existing spectrum synthesis programs or
used it in a stand-alone mode to compute line broadening cross sections
for specific transitions.
---------------------------------------------------------
Title: Mg line formation in late-type stellar atmospheres. I. The
model atom
Authors: Osorio, Y.; Barklem, P. S.; Lind, K.; Belyaev, A. K.;
Spielfiedel, A.; Guitou, M.; Feautrier, N.
2015A&A...579A..53O Altcode: 2015arXiv150407593O
Context. Magnesium is an element of significant astrophysical
importance, often traced in late-type stars using lines of neutral
magnesium, which is expected to be subject to departures from local
thermodynamic equilibrium (LTE). The importance of Mg , together
with the unique range of spectral features in late-type stars probing
different parts of the atom, as well as its relative simplicity from an
atomic physics point of view, makes it a prime target and test bed for
detailed ab initio non-LTE modelling in stellar atmospheres. Previous
non-LTE modelling of spectral line formation has, however, been
subject to uncertainties due to lack of accurate data for inelastic
collisions with electrons and hydrogen atoms. <BR /> Aims: In this
paper we build and test a Mg model atom for spectral line formation
in late-type stars with new or recent inelastic collision data and no
associated free parameters. We aim to reduce these uncertainties and
thereby improve the accuracy of Mg non-LTE modelling in late-type
stars. <BR /> Methods: For the low-lying states of Mg i, electron
collision data were calculated using the R-matrix method. Hydrogen
collision data, including charge transfer processes, were taken
from recent calculations by some of us. Calculations for collisional
broadening by neutral hydrogen were also performed where data were
missing. These calculations, together with data from the literature,
were used to build a model atom. This model was then employed in the
context of standard non-LTE modelling in 1D (including average 3D)
model atmospheres in a small set of stellar atmosphere models. First,
the modelling was tested by comparisons with observed spectra of
benchmark stars with well-known parameters. Second, the spectral line
behaviour and uncertainties were explored by extensive experiments
in which sets of collisional data were changed or removed. <BR />
Results: The modelled spectra agree well with observed spectra from
benchmark stars, showing much better agreement with line profile shapes
than with LTE modelling. The line-to-line scatter in the derived
abundances shows some improvements compared to LTE (where the cores
of strong lines must often be ignored), particularly when coupled
with averaged 3D models. The observed Mg emission features at 7 and
12 μm in the spectra of the Sun and Arcturus, which are sensitive to
the collision data, are reasonably well reproduced. Charge transfer
with H is generally important as a thermalising mechanism in dwarfs,
but less so in giants. Excitation due to collisions with H is found to
be quite important in both giants and dwarfs. The R-matrix calculations
for electron collisions also lead to significant differences compared to
when approximate formulas are employed. The modelling predicts non-LTE
abundance corrections ΔA(Mg )<SUB><SUB>NLTE-LTE</SUB></SUB> in dwarfs,
both solar metallicity and metal-poor, to be very small (of order
0.01 dex), even smaller than found in previous studies. In giants,
corrections vary greatly between lines, but can be as large as 0.4
dex. <BR /> Conclusions: Our results emphasise the need for accurate
data of Mg collisions with both electrons and H atoms for precise
non-LTE predictions of stellar spectra, but demonstrate that such data
can be calculated and that ab initio non-LTE modelling without resort
to free parameters is possible. In contrast to Li and Na, where only
the introduction of charge transfer processes has led to differences
with respect to earlier non-LTE modelling, the more complex case of Mg
finds changes due to improvements in the data for collisional excitation
by electrons and hydrogen atoms, as well as due to the charge transfer
processes. Grids of departure coefficients and abundance corrections
for a range of stellar parameters are planned for a forthcoming paper.
---------------------------------------------------------
Title: Atomic and molecular data for optical stellar spectroscopy
Authors: Heiter, U.; Lind, K.; Asplund, M.; Barklem, P. S.; Bergemann,
M.; Magrini, L.; Masseron, T.; Mikolaitis, Š.; Pickering, J. C.;
Ruffoni, M. P.
2015PhyS...90e4010H Altcode: 2015arXiv150606697H
High-precision spectroscopy of large stellar samples plays a crucial
role for several topical issues in astrophysics. Examples include
studying the chemical structure and evolution of the Milky Way
Galaxy, tracing the origin of chemical elements, and characterizing
planetary host stars. Data are accumulating from instruments that
obtain high-quality spectra of stars in the ultraviolet, optical and
infrared wavelength regions on a routine basis. These instruments
are located at ground-based 2-10 m class telescopes around the world,
in addition to the spectrographs with unique capabilities available at
the Hubble Space Telescope. The interpretation of these spectra requires
high-quality transition data for numerous species, in particular neutral
and singly ionized atoms, and di- or triatomic molecules. We rely
heavily on the continuous efforts of laboratory astrophysics groups
that produce and improve the relevant experimental and theoretical
atomic and molecular data. The compilation of the best available data
is facilitated by databases and electronic infrastructures such as
the NIST Atomic Spectra Database, the VALD database, or the Virtual
Atomic and Molecular Data Centre. We illustrate the current status
of atomic data for optical stellar spectra with the example of the
Gaia-ESO Public Spectroscopic Survey. Data sources for 35 chemical
elements were reviewed in an effort to construct a line list for a
homogeneous abundance analysis of up to 10<SUP>5</SUP> stars.
---------------------------------------------------------
Title: The Gaia-ESO Survey: A globular cluster escapee in the
Galactic halo
Authors: Lind, K.; Koposov, S. E.; Battistini, C.; Marino, A. F.;
Ruchti, G.; Serenelli, A.; Worley, C. C.; Alves-Brito, A.; Asplund,
M.; Barklem, P. S.; Bensby, T.; Bergemann, M.; Blanco-Cuaresma, S.;
Bragaglia, A.; Edvardsson, B.; Feltzing, S.; Gruyters, P.; Heiter,
U.; Jofre, P.; Korn, A. J.; Nordlander, T.; Ryde, N.; Soubiran,
C.; Gilmore, G.; Randich, S.; Ferguson, A. M. N.; Jeffries, R. D.;
Vallenari, A.; Allende Prieto, C.; Pancino, E.; Recio-Blanco, A.;
Romano, D.; Smiljanic, R.; Bellazzini, M.; Damiani, F.; Hill, V.;
de Laverny, P.; Jackson, R. J.; Lardo, C.; Zaggia, S.
2015A&A...575L..12L Altcode: 2015arXiv150203934L
A small fraction of the halo field is made up of stars that share the
light element (Z ≤ 13) anomalies characteristic of second generation
globular cluster (GC) stars. The ejected stars shed light on the
formation of the Galactic halo by tracing the dynamical history of
the clusters, which are believed to have once been more massive. Some
of these ejected stars are expected to show strong Al enhancement at
the expense of shortage of Mg, but until now no such star has been
found. We search for outliers in the Mg and Al abundances of the few
hundreds of halo field stars observed in the first eighteen months of
the Gaia-ESO public spectroscopic survey. One halo star at the base
of the red giant branch, here referred to as 22593757-4648029 is found
to have [ Mg/Fe ] = -0.36 ± 0.04 and [ Al/Fe ] = 0.99 ± 0.08, which
is compatible with the most extreme ratios detected in GCs so far. We
compare the orbit of 22593757-4648029 to GCs of similar metallicity
andfind it unlikely that this star has been tidally stripped with low
ejection velocity from any of the clusters. However, both chemical
and kinematic arguments render it plausible that the star has been
ejected at high velocity from the anomalous GC ω Centauri within
the last few billion years. We cannot rule out other progenitor GCs,
because some may have disrupted fully, and the abundance and orbital
data are inadequate for many of those that are still intact. <P
/>Based on data acquired by the Gaia-ESO Survey, programme ID
188.B-3002. Observations were made with ESO Telescopes at the La Silla
Paranal Observatory.Appendix A is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201425554/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Inelastic silicon-hydrogen collision data for non-LTE
applications in stellar atmospheres
Authors: Belyaev, Andrey K.; Yakovleva, Svetlana A.; Barklem, Paul S.
2014A&A...572A.103B Altcode:
<BR /> Aims: Inelastic processes in low-energy Si + H and Si<SUP>+</SUP>
+ H<SUP>-</SUP> collisions are treated for the states from the ground
state up to the ionic state, in order to provide rate coefficients
needed for non-LTE modeling of Si in cool stellar atmospheres. <BR />
Methods: Electronic molecular structure is determined using a recently
proposed model approach based on an asymptotic method in combination
with available ab initio potentials. Nonadiabatic nuclear dynamics
are treated by means of a combination of multichannel formulas and
the branching-probability-current method, based on the Landau-Zener
model for nonadiabatic transition probabilities. <BR /> Results: Cross
sections and rate coefficients for inelastic processes in Si + H and
Si<SUP>+</SUP> + H<SUP>-</SUP> collisions for all transitions between
26 low-lying states plus the ionic state are calculated. It is shown
that the highest rate coefficient values correspond to the excitation,
de-excitation, ion-pair formation, and mutual neutralization processes
involving the Si(3p4p <SUP>3</SUP>D), Si(3p3d <SUP>3</SUP>F), Si(3p4p
<SUP>1</SUP>D), Si(3p3d <SUP>3</SUP>P), Si(3p4p <SUP>1</SUP>S),
and the ionic Si<SUP>+</SUP> + H<SUP>-</SUP> states. These
processes are likely to be important in non-LTE modeling. <P
/>Tables 2-11 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A103">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A103</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Inelastic silicon-hydrogen
collision data (Belyaev+, 2014)
Authors: Belyaev, A. K.; Yakovleva, S. A. .; Barklem, P. S.
2014yCat..35720103B Altcode: 2014yCat..35729103B
Rate coefficients in cm<SUP>3</SUP>/s for inelastic Si+H and Si<S
collisions for temperatures from T=1000K to T=10000K. <P />(10 data
files).
---------------------------------------------------------
Title: Weak Atomic Diffusion Trends in NGC 6752
Authors: Gruyters, Pieter; Korn, Andreas J.; Barklem, Paul S.
2014IAUS..298..406G Altcode:
Atomic diffusion (AD) is a slow continuous process that depletes
heavy elements such as Fe from the surface layers during the MS
lifetime of a star. As the star evolves to the RGB the effect of
depletion disappears as its deep outer convection zone restores the
original composition in the atmosphere. Mixing processes at work below
the outer convection zone reduce the effect of AD as they hinder the
downward diffusion of heavy elements, and thus a more efficient mixing
will cause flattened diffusion trends. Such additional mixing (AddMix)
seems to be needed to reproduce observed abundance trends. Although the
inclusion of extra mixing in a layer just below the convective envelope
is remarkably successful in describing the observed abundance trends in
NGC 6397 ([Fe/H] = -2.1), the description applied is in no way unique
or physically satisfying. To better understand the physics and place
additional constraints on the possible variation of extra mixing with
stellar parameters such as metallicity, we conducted a study, similar to
that presented in Korn et al. (2007), of another metal-poor GC NGC 6752
([Fe/H] = -1.6). In Fig. 1 we show the results, published in Gruyters
et al. (2013), which shows weak yet systematic abundance trends with
evolutionary phase for Fe, Sc, Ti and Ca. The trends are best explained
by stellar structure models including AD with efficient AddMix. As a
consequence sub-primordial stellar lithium abundances of the stars on
the Spite plateau can be brought up to match the WMAP-calibrated Big
Bang nucleosynthesis predictions to within the mutual 1-sigma errors.
---------------------------------------------------------
Title: On Atomic Diffusion and the Cosmological Lithium Abundance
Authors: Gruyters, Pieter; Korn, Andreas J.; Barklem, Paul S.
2014IAUS..298..407G Altcode:
When it comes to lithium in late-type stars, atomic diffusion
(AD) refers to the slow gravitational settling below the convective
zone. Richard, Michaud & Richter, J. (2005) computed the influence
of diffusion on the lithium abundance with different additional mixing
(AddMix) parameters, after 13.5 Gyr with an initial Li abundance
compatible with BBN. Without AddMix the abundance of lithium
would decrease when the temperature of the star increases. This is
depicted by the dashed green line in the left panel of Fig. 1 and is
in contradiction with the existence of a lithium plateau. But with a
model including ad-hoc AddMix, where the AddMix diffusion coefficient
is given by D <SUB>T</SUB> and is connected to D <SUB>He</SUB>(AD) at
a reference temperature of log T <SUB>0</SUB>=6.25, it is possible to
reproduce the plateau as seen in the figure (solid green line). AD with
AddMix has so far been shown to be at work in two globular clusters (GC)
with different metallicities. Korn et al. (2007) showed the effects
in NGC 6397 at [Fe/H] = -2.1. More recently Gruyters et al. (2013)
have shown smaller effects, but similar in nature, in NGC 6752 at
[Fe/H] = -1.6. The Li abundance for both clusters can be brought in
to agreement with predictions from the cosmic microwave background
radiation and Big Bang nucleosynthesis (CMB+BBN) by using stellar
structure models including AD and AddMix, although with different
efficiencies of AddMix. It seems there is an evolution of AddMix with
metallicity which renders AD less efficient. As AddMix acts only
in the outer regions, helium settling in the core is not affected,
and so the overall evolution (e.g. T <SUB>eff</SUB>-age relation)
will be similar regardless of this parameter.
---------------------------------------------------------
Title: Atomic diffusion and mixing in old stars. IV. Weak abundance
trends in the globular cluster NGC 6752
Authors: Gruyters, P.; Korn, A. J.; Richard, O.; Grundahl, F.; Collet,
R.; Mashonkina, L. I.; Osorio, Y.; Barklem, P. S.
2013A&A...555A..31G Altcode: 2013arXiv1305.1774G
Context. Atomic diffusion in stars can create systematic trends
of surface abundances with evolutionary stage. Globular clusters
offer useful laboratories to put observational constraints on this
theory as one needs to compare abundances in unevolved and evolved
stars, all drawn from the same stellar population. <BR /> Aims:
Atomic diffusion and additional mixing has been shown to be at
work in the globular cluster NGC 6397 at a metallicity of [Fe/H] ~
-2.1. We investigate possible abundance trends in Li, Mg, Ca, Ti, Sc,
and Fe with evolutionary stage in another globular cluster NGC 6752
at a metallicity of [Fe/H] ~ -1.6. This in order to better constrain
stellar structure models including atomic diffusion and additional
mixing. <BR /> Methods: We performed a differential abundance analysis
on VLT/FLAMES-UVES data of 16 stars in four groups between the turnoff
point and the red giant branch. Continuum normalisation of the stellar
spectra was performed in an automated way using DAOSPEC. Differential
abundances relative to the sun were derived by fitting synthetic
spectra to individual lines in the stellar spectrum. <BR /> Results:
We find weak systematic abundance trends with evolutionary phase
for Fe, Sc, Ti, and Ca. The individual trends are weaker than the
trends in NGC 6397 and only significant at the 1-σ level. However,
the combined trend shows a significance on the 2-σ level. The trends
are best explained by stellar-structure models including atomic
diffusion with more efficient additional mixing than needed in NGC
6397. The model allows to correct for sub-primordial stellar lithium
abundances of the stars on the Spite plateau. <BR /> Conclusions:
Abundance trends for groups of elements, differently affected by
atomic diffusion and additional mixing, are identified. Although the
significance of the trends is weak, they all seem to indicate that
atomic diffusion is operational along the evolutionary sequence of
NGC 6752. The trends are weaker than those observed in NGC 6397,
which is perhaps due to more efficient mixing. Using models of
atomic diffusion including efficient additional mixing, we find a
diffusion-corrected primordial lithium abundance of log ɛ(Li) = 2.58
± 0.10, in agreement with WMAP-calibrated Big-Bang nucleosynthesis
predictions within the mutual 1-σ uncertainties. <P />Based on data
collected at the ESO telescopes under programmes 079.D-0645 (A) and
81.D-0253 (A).Tables 7 and 8 are available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: The Most Metal-poor Stars. II. Chemical Abundances of 190
Metal-poor Stars Including 10 New Stars with [Fe/H] <= -3.5
Authors: Yong, David; Norris, John E.; Bessell, M. S.; Christlieb,
N.; Asplund, M.; Beers, Timothy C.; Barklem, P. S.; Frebel, Anna;
Ryan, S. G.
2013ApJ...762...26Y Altcode: 2012arXiv1208.3003Y
We present a homogeneous chemical abundance analysis of 16 elements
in 190 metal-poor Galactic halo stars (38 program and 152 literature
objects). The sample includes 171 stars with [Fe/H] <= -2.5, of
which 86 are extremely metal poor, [Fe/H] <= -3.0. Our program stars
include 10 new objects with [Fe/H] <= -3.5. We identify a sample
of "normal" metal-poor stars and measure the trends between [X/Fe]
and [Fe/H], as well as the dispersion about the mean trend for this
sample. Using this mean trend, we identify objects that are chemically
peculiar relative to "normal" stars at the same metallicity. These
chemically unusual stars include CEMP-no objects, one star with high
[Si/Fe], another with high [Ba/Sr], and one with unusually low [X/Fe]
for all elements heavier than Na. The Sr and Ba abundances indicate
that there may be two nucleosynthetic processes at lowest metallicity
that are distinct from the main r-process. Finally, for many elements,
we find a significant trend between [X/Fe] versus T <SUB>eff</SUB>,
which likely reflects non-LTE and/or three-dimensional effects. Such
trends demonstrate that care must be exercised when using abundance
measurements in metal-poor stars to constrain chemical evolution and/or
nucleosynthesis predictions. <P />This paper includes data gathered
with the 6.5 m Magellan Telescopes located at Las Campanas Observatory,
Chile. <P />Based on observations collected at the European Organisation
for Astronomical Research in the Southern Hemisphere, Chile (proposal
281.D-5015).
---------------------------------------------------------
Title: The Most Metal-poor Stars. I. Discovery, Data, and Atmospheric
Parameters
Authors: Norris, John E.; Bessell, M. S.; Yong, David; Christlieb,
N.; Barklem, P. S.; Asplund, M.; Murphy, Simon J.; Beers, Timothy C.;
Frebel, Anna; Ryan, S. G.
2013ApJ...762...25N Altcode: 2012arXiv1208.2999N
We report the discovery of 34 stars in the Hamburg/ESO Survey for
metal-poor stars and the Sloan Digital Sky Survey that have [Fe/H] <~
-3.0. Their median and minimum abundances are [Fe/H] = -3.1 and -4.1,
respectively, while 10 stars have [Fe/H] < -3.5. High-resolution,
high signal-to-noise spectroscopic data—equivalent widths and
radial velocities—are presented for these stars, together with
an additional four objects previously reported or currently being
investigated elsewhere. We have determined the atmospheric parameters,
effective temperature (T <SUB>eff</SUB>), and surface gravity (log g),
which are critical in the determination of the chemical abundances and
the evolutionary status of these stars. Three techniques were used to
derive these parameters. Spectrophotometric fits to model atmosphere
fluxes were used to derive T <SUB>eff</SUB>, log g, and an estimate of
E(B - V); Hα, Hβ, and Hγ profile fitting to model atmosphere results
provided the second determination of T <SUB>eff</SUB> and log g; and
finally, we used an empirical T <SUB>eff</SUB>-calibrated Hδ index,
for the third, independent T <SUB>eff</SUB> determination. The three
values of T <SUB>eff</SUB> are in good agreement, although the profile
fitting may yield systematically cooler T <SUB>eff</SUB> values, by
~100 K. This collective data set will be analyzed in future papers
in the present series to utilize the most metal-poor stars as probes
of conditions in the early universe. <P />This paper includes data
obtained with the ANU 2.3 m Telescope at Siding Spring Observatory,
Australia; the Magellan Clay Telescope at Las Campanas Observatory,
Chile; the Keck I Telescope at the W. M. Keck Observatory, Hawaii, USA;
and the VLT (Kueyen) of the European Southern Observatory, Paranal,
Chile (proposal 281.D-5015).
---------------------------------------------------------
Title: The Most Metal-poor Stars. III. The Metallicity Distribution
Function and Carbon-enhanced Metal-poor Fraction
Authors: Yong, David; Norris, John E.; Bessell, M. S.; Christlieb,
N.; Asplund, M.; Beers, Timothy C.; Barklem, P. S.; Frebel, Anna;
Ryan, S. G.
2013ApJ...762...27Y Altcode: 2012arXiv1208.3016Y
We examine the metallicity distribution function (MDF) and fraction
of carbon-enhanced metal-poor (CEMP) stars in a sample that includes
86 stars with [Fe/H] <= -3.0, based on high-resolution, high
signal-to-noise spectroscopy, of which some 32 objects lie below [Fe/H]
= -3.5. After accounting for the completeness function, the "corrected"
MDF does not exhibit the sudden drop at [Fe/H] = -3.6 that was found in
recent samples of dwarfs and giants from the Hamburg/ESO survey. Rather,
the MDF decreases smoothly down to [Fe/H] = -4.1. Similar results are
obtained from the "raw" MDF. We find that the fraction of CEMP objects
below [Fe/H] = -3.0 is 23% ± 6% and 32% ± 8% when adopting the Beers
& Christlieb and Aoki et al. CEMP definitions, respectively. The
former value is in fair agreement with some previous measurements,
which adopt the Beers & Christlieb criterion. <P />This paper
includes data gathered with the 6.5 m Magellan Telescopes located at
Las Campanas Observatory, Chile. <P />Based on observations collected
at the European Organisation for Astronomical Research in the Southern
Hemisphere, Chile (proposal 281.D-5015).
---------------------------------------------------------
Title: The Most Metal-poor Stars. IV. The Two Populations with [Fe/H]
<~ -3.0
Authors: Norris, John E.; Yong, David; Bessell, M. S.; Christlieb, N.;
Asplund, M.; Gilmore, Gerard; Wyse, Rosemary F. G.; Beers, Timothy C.;
Barklem, P. S.; Frebel, Anna; Ryan, S. G.
2013ApJ...762...28N Altcode: 2012arXiv1211.3157N
We discuss the carbon-normal and carbon-rich populations of Galactic
halo stars having [Fe/H] lsim -3.0, utilizing chemical abundances from
high-resolution, high signal-to-noise model-atmosphere analyses. The
C-rich population represents ~28% of stars below [Fe/H] = -3.1, with the
present C-rich sample comprising 16 CEMP-no stars, and two others with
[Fe/H] ~ -5.5 and uncertain classification. The population is O-rich
([O/Fe] gsim +1.5); the light elements Na, Mg, and Al are enhanced
relative to Fe in half the sample; and for Z > 20 (Ca) there is
little evidence for enhancements relative to solar values. These results
are best explained in terms of the admixing and processing of material
from H-burning and He-burning regions as achieved by nucleosynthesis in
zero-heavy-element models in the literature of "mixing and fallback"
supernovae (SNe); of rotating, massive, and intermediate-mass stars;
and of Type II SNe with relativistic jets. The available (limited)
radial velocities offer little support for the C-rich stars with
[Fe/H] < -3.1 being binary. More data are required before one
could conclude that binarity is key to an understanding of this
population. We suggest that the C-rich and C-normal populations result
from two different gas cooling channels in the very early universe of
material that formed the progenitors of the two populations. The first
was cooling by fine-structure line transitions of C II and O I (to form
the C-rich population); the second, while not well defined (perhaps
dust-induced cooling?), led to the C-normal group. In this scenario,
the C-rich population contains the oldest stars currently observed.
---------------------------------------------------------
Title: The influence of electron collisions on non-LTE Li line
formation in stellar atmospheres
Authors: Osorio, Yeisson; Barklem, Paul; Lind, Karin; Asplund, Martin
2012JPhCS.388d2018O Altcode: 2011arXiv1102.1556O
The influence of the uncertainties in the rate coefficient data for
electron-impact excitation and ionization on non-LTE Li line formation
in cool stellar atmospheres is investigated. We examine the electron
collision data used in previous non-LTE calculations and compare them
to our own calculations using the R-matrix with pseudostates (RMPS)
method and to other calculations found in the literature.
---------------------------------------------------------
Title: Precise effective temperatures of solar analog stars
Authors: Cornejo-Espinoza, D.; Ramírez, I.; Barklem, P. S.;
Guevara-Day, W.
2012IAUS..286..328C Altcode:
We perform a study of 62 solar analog stars to compute their effective
temperatures (T <SUB>eff</SUB>) using the Balmer line wing fitting
procedure and compare them with T <SUB>eff</SUB> values obtained using
other commonly employed methods. We use observed Hα spectral lines and
a fine grid of theoretical LTE model spectra calculated with the best
available atomic data and most recent quantum theory. Our spectroscopic
data are of very high quality and have been carefully normalized
to recover the proper shape of the Hα line profile. We obtain T
<SUB>eff</SUB> values with internal errors of about 25K. Comparison
of our results with those from other methods shows reasonably good
agreement. Then, combining T <SUB>eff</SUB> values obtained from four
independent techniques, we are able to determine final T <SUB>eff</SUB>
values with errors of about 10K.
---------------------------------------------------------
Title: Precise Effective Temperatures of Solar Analog Stars
Authors: Cornejo, D.; Ramirez, I.; Barklem, P. S.
2012arXiv1206.0750C Altcode:
We perform a study of 62 solar analog stars to compute their effective
temperatures (Teff) using the Balmer line wing fitting procedure and
compare them with Teff values obtained using other commonly employed
methods. We use observed H-alpha spectral lines and a fine grid of
theoretical LTE model spectra calculated with the best available atomic
data and most recent quantum theory. Our spectroscopic data are of
very high quality and have been carefully normalized to recover the
proper shape of the H-alpha line profile. We obtain Teff values with
internal errors of about 25 K. Comparison of our results with those
from other methods shows reasonably good agreement. Then, combining
Teff values obtained from four independent techniques, we are able to
determine final Teff values with errors of about 10 K.
---------------------------------------------------------
Title: Inelastic Mg+H collision data for non-LTE applications in
stellar atmospheres
Authors: Barklem, P. S.; Belyaev, A. K.; Spielfiedel, A.; Guitou,
M.; Feautrier, N.
2012A&A...541A..80B Altcode: 2012arXiv1203.4877B
Rate coefficients for inelastic Mg+H collisions are calculated for all
transitions between the lowest seven levels and the ionic state (charge
transfer), namely Mg(3s<SUP>2</SUP> <SUP>1</SUP>S, 3s3p <SUP>3</SUP>P,
3s3p <SUP>1</SUP>P, 3s4s <SUP>3</SUP>S, 3s4s <SUP>1</SUP>S, 3s3d
<SUP>1</SUP>D, 3s4p <SUP>3</SUP>P)+H(1s) and Mg<SUP>+</SUP>(3s
<SUP>2</SUP>S)+H<SUP>-</SUP>. The rate coefficients are based on
cross-sections from full quantum scattering calculations, which are
themselves based on detailed quantum chemical calculations for the
MgH molecule. The data are needed for non-LTE applications in cool
astrophysical environments, especially cool stellar atmospheres, and
are presented for a temperature range of 500-8000 K. From consideration
of the sensitivity of the cross-sections to various uncertainties in
the calculations, most importantly input quantum chemical data and
the numerical accuracy of the scattering calculations, a measure of
the possible uncertainties in the rate coefficients is estimated.
---------------------------------------------------------
Title: Cross sections for low-energy inelastic Mg + H and
Mg<SUP>+</SUP> + H<SUP>-</SUP> collisions
Authors: Belyaev, A. K.; Barklem, P. S.; Spielfiedel, A.; Guitou,
M.; Feautrier, N.; Rodionov, D. S.; Vlasov, D. V.
2012PhRvA..85c2704B Altcode:
We report full quantum scattering calculations for low-energy
near-threshold inelastic cross sections in Mg + H and Mg<SUP>+</SUP>
+ H<SUP>-</SUP> collisions. The calculations include all transitions
between the eight lowest adiabatic MgH(<SUP>2</SUP>Σ<SUP>+</SUP>)
molecular states, with the uppermost of those diabatically extended to
the ionic molecular state in the asymptotic region. This allows us to
treat the excitation processes between the seven lowest atomic states
of magnesium in collisions with hydrogen atoms, as well as the ion-pair
production and the mutual neutralization processes. The collision energy
range is from threshold up to 10 eV. These results are important for
astrophysical modeling of spectra in stellar atmospheres. The processes
in question are carefully examined and several process mechanisms are
found. Some mechanisms are determined by interactions between ionic and
covalent configurations at relatively large internuclear distances,
while others are based on short-range nonadiabatic regions due to
interactions between covalent configurations.
---------------------------------------------------------
Title: VizieR Online Data Catalog: HERES VI. Galactic chemical
evolution of Si and C (Zhang+, 2011)
Authors: Zhang, L.; Karlsson, T.; Christlieb, N.; Korn, A. J.; Barklem,
P. S.; Zhao, G.
2011yCat..35280092Z Altcode: 2011yCat..35289092Z
The present work is based on the spectra of 253 HERES stars. The
sample selection and observations are described in Christlieb et
al. (2004A&A...428.1027C). For the convenience of the reader, we
repeat here that the spectra were obtained with the Ultraviolet-Visual
Echelle Spectrograph (UVES) mounted on the 8m Unit Telescope 2 (Kueyen)
of the Very Large Telescope (VLT). <P />(1 data file).
---------------------------------------------------------
Title: On inelastic hydrogen atom collisions in stellar atmospheres
Authors: Barklem, P. S.; Belyaev, A. K.; Guitou, M.; Feautrier, N.;
Gadéa, F. X.; Spielfiedel, A.
2011A&A...530A..94B Altcode: 2011arXiv1104.1334B
The influence of inelastic hydrogen atom collisions on non-LTE spectral
line formation has been, and remains to be, a significant source of
uncertainty for stellar abundance analyses, due to the difficulty
in obtaining accurate data for low-energy atomic collisions either
experimentally or theoretically. For lack of a better alternative,
the classical "Drawin formula" is often used. Over recent decades, our
understanding of these collisions has improved markedly, predominantly
through a number of detailed quantum mechanical calculations. In this
paper, the Drawin formula is compared with the quantum mechanical
calculations both in terms of the underlying physics and the resulting
rate coefficients. It is shown that the Drawin formula does not
contain the essential physics behind direct excitation by H atom
collisions, the important physical mechanism being quantum mechanical
in character. Quantitatively, the Drawin formula compares poorly with
the results of the available quantum mechanical calculations, usually
significantly overestimating the collision rates by amounts that vary
markedly between transitions.
---------------------------------------------------------
Title: The influence of electron collisions on non-LTE Li line
formation in stellar atmospheres
Authors: Osorio, Y.; Barklem, P. S.; Lind, K.; Asplund, M.
2011A&A...529A..31O Altcode:
The influence of the uncertainties in the rate coefficient data for
electron-impact excitation and ionization on non-LTE Li line formation
in cool stellar atmospheres is investigated. We examine the electron
collision data used in previous non-LTE calculations and compare them to
recent calculations that use convergent close-coupling (CCC) techniques
and to our own calculations using the R-matrix with the pseudostates
(RMPS) method. We find excellent agreement between rate coefficients
from the CCC and RMPS calculations, and reasonable agreement between
these data and the semi-empirical data used in non-LTE calculations
up to now. The results of non-LTE calculations using the old and new
data sets are compared and only small differences found: about 0.01
dex (~2%) or less in the abundance corrections. We therefore conclude
that the influence on non-LTE calculations of uncertainties in the
electron collision data is negligible. Indeed, together with the
collision data for the charge exchange process Li(3s) + H ⇌ Li<SUP>
+ </SUP> + H<SUP> - </SUP> now available, and barring the existence
of an unknown important collisional process, the collisional data in
general is not a source of significant uncertainty in non-LTE Li line
formation calculations.
---------------------------------------------------------
Title: Non-LTE calculations for neutral Na in late-type stars using
improved atomic data
Authors: Lind, K.; Asplund, M.; Barklem, P. S.; Belyaev, A. K.
2011A&A...528A.103L Altcode: 2011arXiv1102.2160L
Neutral sodium is a minority species in the atmospheres of late-type
stars, and line formation in local thermodynamic equilibrium (LTE) is
often a poor assumption, in particular for strong lines. We present
an extensive grid of non-LTE calculations for several Na I lines in
cool stellar atmospheres, including metal-rich and metal-poor dwarfs
and giants. For the first time, we constructed a Na model atom that
incorporates accurate quantum mechanical calculations for collisional
excitation and ionisation by electrons as well as collisional excitation
and charge exchange reactions with neutral hydrogen. Similar to Li
I, the new rates for hydrogen impact excitation do not affect the
statistical equilibrium calculations, while charge exchange reactions
have a small but non-negligible influence. The presented LTE and non-LTE
curves-of-growth can be interpolated to obtain non-LTE abundances and
abundance corrections for arbitrary stellar parameter combinations and
line strengths. The typical corrections for weak lines are -0.1... -0.2
dex, whereas saturated lines may overestimate the abundance in LTE by
more than 0.5 dex. The non-LTE Na abundances appear very robust with
respect to uncertainties in the input collisional data.
---------------------------------------------------------
Title: The Hamburg/ESO R-process Enhanced Star survey (HERES). VI. The
Galactic chemical evolution of silicon
Authors: Zhang, L.; Karlsson, T.; Christlieb, N.; Korn, A. J.; Barklem,
P. S.; Zhao, G.
2011A&A...528A..92Z Altcode: 2010arXiv1006.3594Z
<BR /> Aims: To obtain detailed silicon abundances of metal-poor stars,
we aim to explore the correlation between the abundance ratios and
the stellar parameters and the chemical enrichment of the interstellar
medium (ISM). <BR /> Methods: We determined the silicon abundances of
253 metal-poor stars in the metallicity range -4 < [Fe/H] < -1.5,
based on non-local thermodynamic equilibrium (NLTE) line formation
calculations of neutral silicon and high-resolution spectra obtained
with VLT-UT2/UVES. <BR /> Results: The T<SUB>eff</SUB> dependence
of [Si/Fe] noticed in previous investigations is diminished in our
abundance analysis owing to the inclusion of NLTE effects. An increasing
slope of [Si/Fe] towards decreasing metallicity is present in our
results, in agreement with Galactic chemical evolution models. Intrinsic
scatter of [Si/Fe] in our sample is small. We identified two dwarfs with
[Si/Fe] ~ +1.0: HE 0131-3953, and HE 1430-1123. These main-sequence
turnoff stars are also carbon-enhanced. They may have been pre-enriched
by sub-luminous supernovae. <BR /> Conclusions: The small intrinsic
scatter of [Si/Fe] in our sample may imply that these stars formed
in a region where the yields of type II supernovae were mixed into
a large volume, or that the formation of these stars was strongly
clustered, even if the ISM was enriched by single SNa II in a small
mixing volume. <P />Based on observations collected at the European
Southern Observatory, Paranal, Chile (Proposal numbers 170.D-0010,
and 280.D-5011).Table 3 is only available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Multichannel excitation cross sections of sodium atoms at
slow collisions with hydrogen atoms
Authors: Vlasov, D. V.; Barklem, P. S.; Belyaev, A. K.
2011OptSp.110..321V Altcode:
Excitation cross sections at slow collisions of hydrogen and
sodium atoms are calculated based on two sets of quantum-chemical
data. The results of calculations permit one to conclude that, upon
the excitation of the sodium atom from the ground state in the region
of near-threshold energies, the cross sections are highly sensitive to
matrix nonadiabaticity elements. In addition, the matrix nonadiabaticity
element was varied for the transition 3 s → 3 p of the sodium atom
at fixed collision energy near the reaction threshold. It was found
that the variation leads to a significant change in the excitation
cross section 3 s → 3 p, and the range of the energetic dependence
of this cross section was determined.
---------------------------------------------------------
Title: Inelastic Mg+H collision processes at low energies
Authors: Guitou, M.; Belyaev, A. K.; Barklem, P. S.; Spielfiedel,
A.; Feautrier, N.
2011JPhB...44c5202G Altcode:
Full quantum scattering calculations of cross sections for
low-energy near-threshold inelastic Mg + H collisions are reported,
such processes being of interest for modelling of Mg spectral
lines in stellar atmospheres. The calculations are made for three
transitions between the ground and two lowest excited Mg states,
Mg(3s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB>), Mg(3s3p <SUP>3</SUP>P)
and Mg(3s3p <SUP>1</SUP>P). The calculations are based on adiabatic
potentials and nonadiabatic couplings for the three low-lying
<SUP>2</SUP>Σ<SUP>+</SUP> and the first two <SUP>2</SUP>Π states,
calculated using large active spaces and basis sets. Non-adiabatic
regions associated with radial couplings at avoided ionic crossings
in the <SUP>2</SUP>Σ<SUP>+</SUP> molecular potentials are found
to be the main mechanism for excitation. Cross sections of similar
order of magnitude to those obtained in Li + H and Na + H collisions
are found. This, together with the fact that the same mechanism is
important, suggests that as has been found earlier for Li and Na,
processes such as ion pair production may be important in astrophysical
modelling of Mg, and motivates continued study of this system including
all states up to and including the ionic limit.
---------------------------------------------------------
Title: Inelastic Na+H collision data for non-LTE applications in
stellar atmospheres
Authors: Barklem, P. S.; Belyaev, A. K.; Dickinson, A. S.; Gadéa,
F. X.
2010A&A...519A..20B Altcode: 2010arXiv1006.5164B
Rate coefficients for inelastic Na+H collisions are calculated for all
transitions between the ten levels up to and including the ionic state
(ion-pair production), namely Na(3s,3p,4s,3d,4p,5s,4d,4f,5p)+H(1s)
and Na<SUP>+</SUP>+H<SUP>-</SUP>. The calculations are based on recent
full quantum scattering cross-section calculations. The data are needed
for non-LTE applications in cool astrophysical environments, especially
cool stellar atmospheres, and are presented for a temperature range of
500-8000 K. From consideration of the sensitivity of the cross-sections
to input quantum chemical data and the results of different methods for
the scattering calculations, a measure of the possible uncertainties
in the rate coefficients is estimated.
---------------------------------------------------------
Title: VizieR Online Data Catalog: HE 2327-5642 abundance analysis
(Mashonkina+, 2010)
Authors: Mashonkina, L.; Christlieb, N.; Barklem, P. S.; Hill, V.;
Beers, T. C.; Velichko, A.
2010yCat..35160046M Altcode: 2010yCat..35169046M
The photometry was taken from Beers et al. 2007
(Cat. J/ApJS/168/128). High-quality spectra of this star was acquired
during May-November 2005 with the VLT and UVES in dichroic mode. The
BLUE390+RED580 (4h total integration time) and BLUE437+RED860 (10h)
standard settings were employed to ensure a wide wavelength coverage. <P
/>(3 data files).
---------------------------------------------------------
Title: The Hamburg/ESO R-process enhanced star survey
(HERES). V. Detailed abundance analysis of the r-process enhanced
star HE 2327-5642
Authors: Mashonkina, L.; Christlieb, N.; Barklem, P. S.; Hill, V.;
Beers, T. C.; Velichko, A.
2010A&A...516A..46M Altcode: 2010arXiv1003.3571M
<BR /> Aims: We present a detailed abundance analysis of a strongly
r-process enhanced giant star discovered in the HERES project,
HE 2327-5642, for which [Fe/H] = -2.78, [r/Fe] = +0.99. <BR />
Methods: We determined the stellar parameters and element abundances
by analyzing the high-quality VLT/UVES spectra. The surface gravity
was calculated from the non-local thermodynamic equilibrium (NLTE)
ionization balance between ion{Fe}{i} and ion{Fe}{ii}, and ion{Ca}{i}
and ion{Ca}{ii}. <BR /> Results: Accurate abundances for a total of
40 elements and for 23 neutron-capture elements beyond Sr and up to
Th were determined in HE 2327-5642. For every chemical species, the
dispersion in the single line measurements around the mean does not
exceed 0.11 dex. The heavy element abundance pattern of HE 2327-5642 is
in excellent agreement with those previously derived for other strongly
r-process enhanced stars, such as CS 22892-052, CS 31082-001, and HE
1219-0312. Elements in the range from Ba to Hf match the scaled Solar
r-process pattern very well. No firm conclusion can be drawn about the
relationship between the fisrt neutron-capture peak elements, Sr to Pd,
in HE 2327-5642 and the Solar r-process, due to the uncertainty in the
Solar r-process. A clear distinction in Sr/Eu abundance ratios was
found between the halo stars of different europium enhancement. The
strongly r-process enhanced stars contain a low Sr/Eu abundance ratio
at [Sr/Eu] = -0.92 ± 0.13, while the stars with 0 < [Eu/Fe] <
1 and [Eu/Fe] < 0 have 0.36 dex and 0.93 dex higher Sr/Eu values,
respectively. Radioactive dating for HE 2327-5642 with the observed
thorium and rare-earth element abundance pairs results in an average
age of 13.3 Gyr, when based on the high-entropy wind calculations,
and 5.9 Gyr, when using the Solar r-residuals. We propose that HE
2327-5642 is a radial-velocity variable based on our high-resolution
spectra covering 4.3 years. <P />Based on observations collected at
the European Southern Observatory, Paranal, Chile (Proposal numbers
170.D-0010, and 280.D-5011).Table 8 is only available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Abundances of Population II stars
in NGC 6397 (Lind+, 2008)
Authors: Lind, K.; Korn, A. J.; Barklem, P. S.; Grundahl, F.
2010yCat..34900777L Altcode:
The target selection for the spectroscopic study is based on Stroemgren
uvby photometry. The photometric observations were collected with
the DFOSC instrument on the 1.5m telescope on La Silla, Chile, in
1997. Additional BVI photometric data were obtained in 2005. <P />All
spectroscopic data were collected in Service Mode, with the fibre-fed,
multi-object, medium-high resolution spectrograph FLAMES/GIRAFFE at
ESO-VLT. FLAMES allows for 132 objects to be observed simultaneously,
with GIRAFFE in MEDUSA mode, between 2005 Mar 23 and Apr 04. <P />(2
data files).
---------------------------------------------------------
Title: Cross sections for low-energy inelastic H + Na collisions
Authors: Belyaev, A. K.; Barklem, P. S.; Dickinson, A. S.; Gadéa,
F. X.
2010PhRvA..81c2706B Altcode:
Full quantum-scattering calculations are reported for low-energy
near-threshold inelastic collision cross sections for H+Na. The
calculations include transitions between all levels up to and including
the ionic state (ion-pair production) for collision energies from the
threshold up to 10 eV. These results are important for astrophysical
modeling of spectra in stellar atmospheres. Results for the 3s-3p
excitation are carefully examined using three different quantum
chemistry input data sets, and large differences are found near
the threshold. The differences are found to be predominantly due to
differences in the radial coupling rather than potentials and are also
found not to relate to differences in couplings in a simple manner. In
fact, of the three input couplings, the two that are most similar
give the cross sections with the largest differences. The 3s-3p cross
sections show orbiting resonances which have been seen in earlier
studies, while Feshbach resonances associated with closed channels
were also found to be present in the low-energy cross sections for
some transitions.
---------------------------------------------------------
Title: Detailed abundance analysis of the very metal-poor, r-process
enhanced star HE 2327-5642
Authors: Mashonkina, L.; Christlieb, N.; Barklem, P.; Hill, V.; Beers,
T. C.; Velichko, A.
2010nuco.confE.272M Altcode: 2010PoS...100E.272M
No abstract at ADS
---------------------------------------------------------
Title: The stellar content of the Hamburg/ESO survey. V. The
metallicity distribution function of the Galactic halo
Authors: Schörck, T.; Christlieb, N.; Cohen, J. G.; Beers, T. C.;
Shectman, S.; Thompson, I.; McWilliam, A.; Bessell, M. S.; Norris,
J. E.; Meléndez, J.; Ramírez, S.; Haynes, D.; Cass, P.; Hartley,
M.; Russell, K.; Watson, F.; Zickgraf, F. -J.; Behnke, B.; Fechner,
C.; Fuhrmeister, B.; Barklem, P. S.; Edvardsson, B.; Frebel, A.;
Wisotzki, L.; Reimers, D.
2009A&A...507..817S Altcode: 2008arXiv0809.1172S
We determine the metallicity distribution function (MDF) of the
Galactic halo by means of a sample of 1638 metal-poor stars selected
from the Hamburg/ESO objective-prism survey (HES). The sample was
corrected for minor biases introduced by the strategy for spectroscopic
follow-up observations of the metal-poor candidates, namely “best
and brightest stars first”. Comparison of the metallicities [Fe/H]
of the stars determined from moderate-resolution (i.e., R∼ 2000)
follow-up spectra with results derived from abundance analyses based
on high-resolution spectra (i.e., R>20 000) shows that the [Fe/H]
estimates used for the determination of the halo MDF are accurate to
within 0.3 dex, once highly C-rich stars are eliminated. We determined
the selection function of the HES, which must be taken into account
for a proper comparison between the HES MDF with MDFs of other
stellar populations or those predicted by models of Galactic chemical
evolution. The latter show a reasonable agreement with the overall shape
of the HES MDF for [Fe/H] > -3.6, but only a model of Salvadori et
al. (2007) with a critical metallicity for low-mass star formation of
Z_cr=10<SUP>-3.4</SUP>~Z<SUB>⊙</SUB> reproduces the sharp drop at
[Fe/H] ∼ -3.6 present in the HES MDF. Although currently about ten
stars at [Fe/H] < -3.6 are known, the evidence for the existence
of a tail of the halo MDF extending to [Fe/H] ∼ -5.5 is weak from
the sample considered in this paper, because it only includes two stars
[Fe/H] < -3.6. Therefore, a comparison with theoretical models has to
await larger statistically complete and unbiased samples. A comparison
of the MDF of Galactic globular clusters and of dSph satellites to the
Galaxy shows qualitative agreement with the halo MDF, derived from the
HES, once the selection function of the latter is included. However,
statistical tests show that the differences between these are still
highly significant. <P />Based on observations collected at Las Campanas
Observatory, Palomar Observatory, Siding Spring Observatory, and the
European Southern Observatory (Proposal IDs 69.D-0130, 170.D-0010,
073.D-0555, and 081.D-0596).
---------------------------------------------------------
Title: The Hamburg/ESO R-process enhanced star survey
(HERES). IV. Detailed abundance analysis and age dating of the
strongly r-process enhanced stars CS 29491-069 and HE 1219-0312
Authors: Hayek, W.; Wiesendahl, U.; Christlieb, N.; Eriksson, K.;
Korn, A. J.; Barklem, P. S.; Hill, V.; Beers, T. C.; Farouqi, K.;
Pfeiffer, B.; Kratz, K. -L.
2009A&A...504..511H Altcode: 2009arXiv0910.0707H
We report on a detailed abundance analysis of two strongly
r-process enhanced, very metal-poor stars newly discovered in
the HERES project, <ASTROBJ>CS 29491-069</ASTROBJ> ([Fe/H]=-2.51,
[r/Fe]=+1.1) and <ASTROBJ>HE 1219-0312</ASTROBJ> ([Fe/H]=-2.96,
[r/Fe]=+1.5). The analysis is based on high-quality VLT/UVES spectra
and MARCS model atmospheres. We detect lines of 15 heavy elements in
the spectrum of <ASTROBJ>CS 29491-069</ASTROBJ>, and 18 in <ASTROBJ>HE
1219-0312</ASTROBJ>; in both cases including the Th II 4019 Å
line. The heavy-element abundance patterns of these two stars are
mostly well-matched to scaled solar residual abundances not formed
by the s-process. We also compare the observed pattern with recent
high-entropy wind (HEW) calculations, which assume core-collapse
supernovae of massive stars as the astrophysical environment for the
r-process, and find good agreement for most lanthanides. The abundance
ratios of the lighter elements strontium, yttrium, and zirconium, which
are presumably not formed by the main r-process, are reproduced well by
the model. Radioactive dating for <ASTROBJ>CS 29491-069</ASTROBJ> with
the observed thorium and rare-earth element abundance pairs results in
an average age of 9.5 Gyr, when based on solar r-process residuals, and
17.6 Gyr, when using HEW model predictions. Chronometry seems to fail
in the case of <ASTROBJ>HE 1219-0312</ASTROBJ>, resulting in a negative
age due to its high thorium abundance. <ASTROBJ>HE 1219-0312</ASTROBJ>
could therefore exhibit an overabundance of the heaviest elements,
which is sometimes called an “actinide boost”. <P />Based on
observations collected at the European Southern Observatory, Paranal,
Chile (Proposal Number 170.D-0010). Table 8 is only available in
electronic form at http://www.aanda.org
---------------------------------------------------------
Title: Departures from LTE for neutral Li in late-type stars
Authors: Lind, K.; Asplund, M.; Barklem, P. S.
2009A&A...503..541L Altcode: 2009arXiv0906.0899L
We perform non-LTE calculations of lithium in late-type stars for
a wide range of stellar parameters, including quantum mechanical
cross-sections for collisions with neutral hydrogen and the negative
hydrogen ion. Non-LTE abundance corrections for the lithium resonance
line at 670.7 nm and the subordinate line at 610.3 nm, are calculated
using 1D MARCS model atmospheres spanning a grid T_eff = [4000, 8000]
K, log g = [1.0, 5.0], and [Fe/H] = [0.0, -3.0], for lithium abundances
in the range A(Li) = [-0.3, 4.2]. The competing effects of ultraviolet
over-ionization and photon losses in the resonance line govern the
behaviour of the non-LTE effects with stellar parameters and lithium
abundance. The size and sign of the non-LTE abundance corrections
vary significantly over the grid for the 670.7 nm line, but are
typically positive and below 0.15 dex for the 610.3 nm, line. The new
collisional data play a significant role in determining the abundance
corrections. <P />Complete Tables [see full textsee full textsee full
textsee full textsee full text] and [see full textsee full textsee
full textsee full textsee full text] are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/503/541
---------------------------------------------------------
Title: Lithium Abundances of Extremely Metal-Poor Turnoff Stars
Authors: Aoki, Wako; Barklem, Paul S.; Beers, Timothy C.; Christlieb,
Norbert; Inoue, Susumu; García Pérez, Ana E.; Norris, John E.;
Carollo, Daniela
2009ApJ...698.1803A Altcode: 2009arXiv0904.1448A
We have determined Li abundances for eleven metal-poor turnoff
stars, among which eight have [Fe/H] <-3, based on LTE analyses of
high-resolution spectra obtained with the High Dispersion Spectrograph
on the Subaru Telescope. The Li abundances for four of these eight stars
are determined for the first time by this study. Effective temperatures
are determined by a profile analysis of Hα and Hβ. While seven stars
have Li abundances as high as the Spite Plateau value, the remaining
four objects with [Fe/H] <-3 have A(Li) =log (Li/H)+ 12 lsim 2.0,
confirming the existence of extremely metal-poor (EMP) turnoff stars
having low Li abundances, as reported by previous work. The average of
the Li abundances for stars with [Fe/H]<-3 is lower by 0.2 dex than
that of the stars with higher metallicity. No clear constraint on the
metallicity dependence or scatter of the Li abundances is derived from
our measurements for the stars with [Fe/H]<-3. Correlations of the
Li abundance with effective temperatures, with abundances of Na, Mg,
and Sr, and with the kinematical properties are investigated, but no
clear correlation is seen in the EMP star sample. <P />Based on data
collected at the Subaru Telescope, which is operated by the National
Astronomical Observatory of Japan.
---------------------------------------------------------
Title: Neutral oxygen spectral line formation revisited with new
collisional data: large departures from LTE at low metallicity
Authors: Fabbian, D.; Asplund, M.; Barklem, P. S.; Carlsson, M.;
Kiselman, D.
2009A&A...500.1221F Altcode: 2009arXiv0902.4472F
Aims: A detailed study is presented, including estimates of the
impact on elemental abundance analysis, of the non-local thermodynamic
equilibrium (non-LTE) formation of the high-excitation neutral oxygen
777 nm triplet in model atmospheres representative of stars with
spectral types F to K. <BR />Methods: We have applied the statistical
equilibrium code MULTI to a number of plane-parallel MARCS atmospheric
models covering late-type stars (4500 ≤ T_eff ≤ 6500 K, 2 ≤ log
g ≤ 5 [cgs], and -3.5 ≤ [Fe/H] ≤ 0). The atomic model employed
includes, in particular, recent quantum-mechanical electron collision
data. <BR />Results: We confirm that the O i triplet lines form under
non-LTE conditions in late-type stars, suffering negative abundance
corrections with respect to LTE. At solar metallicity, the non-LTE
effect, mainly attributed in previous studies to photon losses in the
triplet itself, is also driven by an additional significant contribution
from line opacity. At low metallicity, the very pronounced departures
from LTE are due to overpopulation of the lower level (3s ^5S^o) of the
transition. Large line opacity stems from triplet-quintet intersystem
electron collisions, a form of coupling previously not considered or
seriously underestimated. The non-LTE effects generally become severe
for models (both giants and dwarfs) with higher T_eff. Interestingly,
in metal-poor turn-off stars, the negative non-LTE abundance corrections
tend to rapidly become more severe towards lower metallicity. When
neglecting H collisions, they amount to as much as |Δlog ɛ_O|
~ 0.9 dex and ~1.2 dex, respectively at [Fe/H] = -3 and [Fe/H]
= -3.5. Even when such collisions are included, the LTE abundance
remains a serious overestimate, correspondingly by |Δlog ɛ_O| ~ 0.5
dex and ~0.9 dex at such low metallicities. Although the poorly known
inelastic hydrogen collisions thus remain an important uncertainty,
the large metallicity-dependent non-LTE effects seem to point to
a resulting “low” (compared to LTE) [O/Fe] in metal-poor halo
stars. <BR />Conclusions: Our results may be important in solving
the long-standing [O/Fe] debate. When applying the derived non-LTE
corrections, the LTE oxygen abundance inferred from the 777 nm permitted
triplet will be decreased substantially at low metallicity. If the
classical Drawin formula is employed for O+H collisions, the derived
[O/Fe] trend becomes almost flat below [Fe/H] ~ -1, in better agreement
with recent literature estimates generally obtained from other oxygen
abundance indicators. A value of [O/Fe] ⪉ +0.5 may therefore be
appropriate, as suggested by standard theoretical models of type II
supernovae nucleosynthetic yields. If neglecting impacts with H atoms
instead, [O/Fe] decreases towards lower [Fe/H], which would open new
questions. Our tests using ATLAS model atmospheres show that, though
non-LTE corrections for metal-poor dwarfs are smaller (by ~0.2 dex
when adopting efficient H collisions) than in the MARCS case, our
main conclusions are preserved, and that the LTE approach tends to
seriously overestimate the O abundance at low metallicity. However,
in order to finally reach consistency between oxygen abundances from
the different available spectral features, it is of high priority to
reduce the large uncertainty regarding H collisions, to undertake a
full investigation of the interplay of non-LTE and 3D effects, and to
clarify the issue of the temperature scale at low metallicity.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Neutral Li in late-type stars
non-LTE calculations (Lind+, 2009)
Authors: Lind, K.; Asplund, M.; Barklem, P. S.
2009yCat..35030541L Altcode:
Non-LTE abundance corrections and equivalent widths for atmospheric
models in the stellar parameter range Teff=[4000,8000]K,
log(g)=[1.0,5.0], [Fe/H]=[0.0,-3.0], and microturbulence
[1.0,5.0]km/s. The lithium abundance ranges between A(Li)=[-0.3,4.2]. An
IDL-code for interpolation between table-values can be obtained on
request to klind(at)eso.org. <P />(2 data files).
---------------------------------------------------------
Title: Hydrogen lines
Authors: Barklem, P. S.
2008PhST..133a4023B Altcode:
Advances in modern detectors have allowed hydrogen Balmer lines to
be used as high-precision diagnostics of effective temperature in F,
G and K stars. Their precision as such a diagnostic is now to a large
degree dependent on our understanding of their formation in stellar
atmospheres. In this paper, I review the current status of Balmer
lines as effective temperature diagnostics and in particular discuss
two aspects of their line formation: (i) the question of whether the
line wings form in Local Thermodynamic Equilibrium (LTE) or not and
(ii) the broadening of the line wings by collisions.
---------------------------------------------------------
Title: A new sample of extremely/ultra metal-poor stars
Authors: García Pérez, A. E.; Christlieb, N.; Ryan, S. G.; Beers,
T. C.; Aoki, W.; Asplund, M.; Barklem, P. S.; Bessell, M. S.; Eriksson,
K.; Frebel, A.; Gustafsson, B.; Korn, A. J.; Nordström, B.; Norris,
J. E.
2008PhST..133a4036G Altcode:
A sample of 30 very metal-poor stars from the Hamburg-European
Southern Observatory (ESO) objective-prism survey have been observed
at high spectral resolution at the Very Large Telescope (VLT) using the
Ultraviolet and Visual Echelle Spectrograph (UVES). Two of the observed
stars are very interesting not only because of their very low iron
content, approximately four orders of magnitude lower than the solar
value, but also because we detected the neutral lithium resonance line
at 670.8 nm. Hydrogen lines suggest that the two observed stars have
effective temperatures around 6000 6250 K and according to isochrones,
they are either on the main sequence or on the subgiant branch, in
which case they would probably be the most metal-poor dwarfs or warm
subgiants with lithium detections known. These detections would allow
to determine more accurately the slope of the trend of the lithium
abundance with [Fe/H] than was possible with samples of unevolved
stars restricted to higher metallicities.
---------------------------------------------------------
Title: Atomic diffusion and mixing in old stars. II. Observations
of stars in the globular cluster NGC 6397 with VLT/FLAMES-GIRAFFE
Authors: Lind, K.; Korn, A. J.; Barklem, P. S.; Grundahl, F.
2008A&A...490..777L Altcode: 2008arXiv0809.0317L
Context: Evolutionary trends in the surface abundances of heavier
elements have recently been identified in the globular cluster NGC
6397 ([Fe/H] = -2), indicating the operation of atomic diffusion
in these stars. Such trends constitute important constraints for
the extent to which diffusion modifies the internal structure and
surface abundances of solar-type, metal-poor stars. <BR />Aims: We
perform an independent check of the reality and size of abundance
variations within this metal-poor globular cluster. <BR />Methods:
Observational data covering a large stellar sample, located between
the cluster turn-off point and the base of the red giant branch, are
homogeneously analysed. The spectroscopic data were obtained with the
medium-high resolution spectrograph FLAMES/GIRAFFE on VLT-UT2 (R ~ 27
000). We derive independent effective-temperature scales from profile
fitting of Balmer lines and by applying colour-T_eff calibrations to
Strömgren uvby and broad-band BVI photometry. An automated spectral
analysis code is used together with a grid of MARCS model atmospheres
to derive stellar surface abundances of Mg, Ca, Ti, and Fe. <BR
/>Results: We identify systematically higher iron abundances for
more evolved stars. The turn-off point stars are found to have 0.13
dex lower surface abundances of iron compared to the coolest, most
evolved stars in our sample. There is a strong indication of a similar
trend in magnesium, whereas calcium and titanium abundances are more
homogeneous. Within reasonable error limits, the obtained abundance
trends are in agreement with the predictions of stellar structure
models including diffusive processes (sedimentation, levitation),
if additional turbulent mixing below the outer convection zone is
included. <P />Based on data collected at European Southern Observatory
(ESO), Paranal, Chile, under program ID 075.D-0125(A). <P />Tables 4
and 5 are only available in electronic form at http://www.aanda.org
---------------------------------------------------------
Title: PREFACE: A Stellar Journey: A symposium in celebration of
Bengt Gustafsson's 65th birthday A Stellar Journey: A symposium in
celebration of Bengt Gustafsson's 65th birthday
Authors: Barklem, P. S.; Korn, A. J.; Plez, B.
2008PhST..133a1001B Altcode:
This volume contains the proceedings of the symposium `A Stellar
Journey: A symposium in celebration of Bengt Gustafsson's 65th birthday'
held at Gustavianum in Uppsala, Sweden, on 23--27 June 2008. We
sincerely thank all the participants who got their contributions to
us despite a quite demanding deadline, enabling us to produce this
festschrift for Bengt in good time following the conference. We
believe these proceedings represent a valuable snapshot of a broad
range of topics in modern stellar physics. <P />The organisation of
this symposium would not have been possible without generous support
from the Swedish Research Council (Vetenskapsr∠det). We are also very
thankful to the Uppsala University Physics Section and the Department
of Physics and Astronomy for their financial and logistic support.
---------------------------------------------------------
Title: VALD — an atomic and molecular database for astrophysics
Authors: Heiter, U.; Barklem, P.; Fossati, L.; Kildiyarova, R.;
Kochukhov, O.; Kupka, F.; Obbrugger, M.; Piskunov, N.; Plez, B.;
Ryabchikova, T.; Stempels, H. C.; Stütz, Ch; Weiss, W. W.
2008JPhCS.130a2011H Altcode:
The VALD database of atomic and molecular data aims to ensure a robust
and consistent analysis of astrophysical spectra. We offer a convenient
e-mail and web-based user interface to a vast collection of spectral
line parameters for all chemical elements and in the future also for
molecules. An international team is working on the following tasks:
collecting line parameters from relevant theoretical and experimental
publications, computing line parameters, evaluating the data quality by
comparison of similar data from different sources and by comparison
with astrophysical observations, and incorporating the data into
VALD. A unique feature of VALD is its capability to provide the most
comprehensive spectral line lists for specific astrophysical plasma
conditions defined by the user.
---------------------------------------------------------
Title: Lithium Abundances in Extremely Metal-Poor Turn-Off Stars
Authors: Aoki, W.; Barklem, P.; Beers, T. C.; Christlieb, N.; Inoue, S.
2008AIPC.1016...37A Altcode:
The Lithium (Li) abundances measured for very metal-poor turn-off
(unevolved) stars have been interpreted as the result of Big Bang
nucleosynthesis. However, the value is lower by a factor of two
or three than the prediction of standard Big Bang nucleosynthesis
models, adopting the cosmological parameters determined by the
measurements of cosmic microwave background radiation with the WMAP
satellite. Moreover, the recent measurements for extremely metal-poor
stars (objects having iron abundances less than 1/1000th solar)
suggest a scatter of the Li abundance, or a possible decreasing trend
with decreasing metallicity. In order to further investigate the Li
production and destruction processes in the very early universe, we
have determined Li abundances for extremely metal-poor stars based
on high-resolution spectra for the resonance line of neutral Li. The
result of our analysis, combined with previous measurements, indicates
that the Li abundances of extremely metal-poor stars are, on average,
lower than those of stars with higher metallicity, while the scatter
or trend of the Li abundance remains unclear. We discuss possible
reasons for the lower Li abundances in extremely metal-poor stars,
such as depletion of Li in low-mass unevolved stars, or destruction
of Li by the first generations of massive progenitors.
---------------------------------------------------------
Title: Atomic Diffusion and Mixing in Old Stars. I. Very Large
Telescope FLAMES-UVES Observations of Stars in NGC 6397
Authors: Korn, A. J.; Grundahl, F.; Richard, O.; Mashonkina, L.;
Barklem, P. S.; Collet, R.; Gustafsson, B.; Piskunov, N.
2007ApJ...671..402K Altcode: 2007arXiv0709.0639K
We present a homogeneous photometric and spectroscopic analysis of
18 stars along the evolutionary sequence of the metal-poor globular
cluster NGC 6397 ([Fe/H]~-2), from the main-sequence turnoff point to
red giants below the bump. The spectroscopic stellar parameters, in
particular stellar parameter differences between groups of stars, are
in good agreement with broadband and Strömgren photometry calibrated
on the infrared flux method. The spectroscopic abundance analysis
reveals, for the first time, systematic trends of iron abundance
with evolutionary stage. Iron is found to be 30% less abundant in the
turnoff point stars than in the red giants. An abundance difference
in lithium is seen between the turnoff point and warm subgiant
stars. The impact of potential systematic errors on these abundance
trends (stellar parameters, the hydrostatic and LTE approximations)
is quantitatively evaluated and found not to alter our conclusions
significantly. Trends for various elements (Li, Mg, Ca, Ti, and Fe)
are compared with stellar structure models including the effects of
atomic diffusion and radiative acceleration. Such models are found
to describe the observed element-specific trends well, if extra
(turbulent) mixing just below the convection zone is introduced. It
is concluded that atomic diffusion and turbulent mixing are largely
responsible for the subprimordial stellar lithium abundances of warm
halo stars. Other consequences of atomic diffusion in old metal-poor
stars are also discussed. <P />Based on observations carried out at
the European Southern Observatory (ESO), Paranal, Chile, under program
ID 075.D-0125(A).
---------------------------------------------------------
Title: The Broadening of Spectral Lines by Collisions with Neutral
Hydrogen Atoms in Cool Stars
Authors: Barklem, Paul S.
2007AIPC..938..111B Altcode:
I review the theory of broadening of metallic spectral lines by neutral
hydrogen atom collisions developed by Anstee, Barklem and O'Mara. I
discuss why the theory works, while is able to retain the wide range
of applicability needed for astrophysical applications. I discuss the
present status of large scale calculations for many spectral lines
for neutral and singly ionized species. Some examples of application
to analysis of cool star spectra will be discussed.
---------------------------------------------------------
Title: Multipole rates for atomic polarization studies: the case
of complex atoms in non-spherically symmetric states colliding with
atomic hydrogen
Authors: Sahal-Bréchot, S.; Derouich, M.; Bommier, V.; Barklem, P. S.
2007A&A...465..667S Altcode:
Context: Interpretation of linearly polarized parameters of the lines of
complex atoms for the second solar spectrum needs a lot of collisional
coefficients which are often poorly known. <BR />Aims: We provide
general and simple formulae giving the coefficients of the atomic master
equation (depolarization, polarization transfer, population transfer,
and relaxation coefficients) for the case of any atomic level (but not
a spherically symmetric) that is perturbed by collisions with hydrogen
atoms. <BR />Methods: We use the theory of the density matrix and
the theory of atomic collisions with a few assumptions (frozen core
and spin neglected during the collision). We only study collisional
transitions between levels of the same configuration with no equivalent
electrons in the external shell, and with the rest of the configuration
(the core) frozen. We use the basis of the T<SUP>k</SUP><SUB>q</SUB>
irreducible spherical tensor operators. <BR />Results: The formulae
giving the depolarization and polarization transfer coefficients due to
collisions with neutral hydrogen for l ≠ 0 levels of complex atoms can
be expressed as a linear combination of the k-pole depolarization and
elastic collisional rate coefficients obtained for simple atoms. <BR
/>Conclusions: .It should be possible to apply this method for fast
calculation of multipole rates for any level having an external shell
l ≠ 0.
---------------------------------------------------------
Title: Non-LTE Balmer line formation in late-type spectra: effects
of atomic processes involving hydrogen atoms
Authors: Barklem, P. S.
2007A&A...466..327B Altcode: 2007astro.ph..2222B
Context: The wings of Balmer lines are often used as effective
temperature diagnostics for late-type (F, G, K) stars under the
assumption they form in local thermodynamic equilibrium (LTE). <BR
/>Aims: Our goal is to investigate the non-LTE excitation and
ionisation of hydrogen and the formation of Balmer lines in
late-type stellar atmospheres, to establish if the assumption of
LTE is justified. Furthermore, we aim to determine which collision
processes are important for the problem; in particular, the role of
collision processes with hydrogen atoms is investigated. <BR />Methods:
A model hydrogen atom for non-LTE calculations has been constructed
accounting for various collision processes using the best available data
from the literature. The processes included are inelastic collisions
with electrons and hydrogen atoms, mutual neutralisation and Penning
ionisation. Non-LTE calculations are performed using the MULTI code
and the MACKKL semi-empirical solar model, and the relative importance
of the collision processes is investigated. Similar calculations
are performed for MARCS theoretical models of other late-type
stellar atmospheres. <BR />Results: Our calculations show electron
collisions alone are not sufficient to establish LTE for the formation
of Balmer line wings. Mutual neutralisation and Penning ionisation
are found to be unimportant. The role of inelastic collisions with
neutral hydrogen is unclear. The available data for these processes
is of questionable quality, and different prescriptions for the rate
coefficents give significantly different results for the Balmer line
wings. <BR />Conclusions: Improved calculations or experimental data
are needed for excitation and, particularly, ionisation of hydrogen
atoms in low-lying states by hydrogen atom impact at near threshold
energies. Until such data are available, the assumption of LTE for
the formation of Balmer line wings in late-type stars is questionable.
---------------------------------------------------------
Title: Electron-impact excitation of neutral oxygen
Authors: Barklem, P. S.
2007A&A...462..781B Altcode: 2006astro.ph..9684B
Aims:Our goal was to calculate transition rates from ground and excited
states in neutral oxygen atoms due to electron collisions for non-LTE
modelling of oxygen in late-type stellar atmospheres, thus enabling
the reliable interpretation of oxygen lines in stellar spectra. <BR
/>Methods: A 38-state R-matrix calculation in LS-coupling has been
performed. Basis orbitals from the literature are adopted, and a large
set of configurations are included to obtain good representations
of the target wave functions. Rate coefficients are calculated by
averaging over a Maxwellian velocity distribution. <BR />Results:
Estimates for the cross sections and rate coefficients are presented for
transitions between the seven lowest LS states of neutral oxygen. The
cross sections for excitation from the ground state compare well with
existing experimental and recent theoretical results.
---------------------------------------------------------
Title: Spin depolarizing effect in collisions with neutral
hydrogen. II. Application to simple/complex ions in spherically
symmetric states
Authors: Derouich, M.; Barklem, P. S.
2007A&A...462.1171D Altcode:
Aims: We develop an accurate and general semi-classical formalism that
deals with the definition and the calculation of the collisional
depolarizing constants of the levels of simple and complex
singly-ionized atoms in arbitrary s-states perturbed by collisions
with hydrogen atoms. The case of ions with hyperfine structure is
investigated fully. <BR />Methods: We obtain potential energy curves
based on the MSMA exchange perturbation theory by employing the Unsöld
approximation. These potentials enter the Schrödinger equation
to determine the collisional T-matrix elements in a semi-classical
description. We use the T-matrix elements for the calculation of the
collisional depolarization rates of simple atoms. Then, we use these
rates to calculate the collisional coefficients in cases of ions
with hyperfine structure. <BR />Results: We evaluate the collisional
depolarization and polarization transfer rates of the ground levels
of the ionized alkaline earth metals Be II, Mg II, Ca II, Sr II, and
Ba II. We study the variation of the collisional rates with effective
principal quantum number n<SUP>*</SUP> characterizing an arbitrary
s-state of a perturbed simple ion. We find that the collisional rates
for simple ions obey simple power laws as a function of n^*. We present
direct and indirect formulations of the problem of the calculation of
the depolarization and polarization transfer rates of levels of complex
atoms and hyperfine levels from those for simple atoms. In particular,
the indirect method allows a quick and simple calculation with its
simple power-law relations. For the state 4s ^2S{1/2} of Ca II, our
computed rate of the destruction of orientation differs from existing
quantum chemistry calculations by only 4% at T=5000 K.
---------------------------------------------------------
Title: Multipole rates for atomic polarization studies: the case
of complex atoms in non-spherically symmetric states colliding with
atomic hydrogen.
Authors: Sahal-Bréchot, S.; Derouich, M.; Bommier, V.; Barklem, P. S.
2007MmSAI..78..197S Altcode:
Interpretation of linearly polarized parameters of the spectral lines
of the second solar spectrum permits to obtain information about
the magnetic field vector of the medium where the spectral lines
are formed, provided suitable theoretical and numerical methods be
applied to extract the physical information. This linear polarization
is modified by the magnetic field and by collisions. In this context,
with a few approximations, we provide in the present paper general
and simple formulae giving the coefficients of the atomic master
equation (depolarization, polarization transfer, population transfer
and relaxation coefficients) for the case of an atom in any (but not
spherically symmetric) level, perturbed by collisions with hydrogen
atoms. It would be possible to apply this method for fast calculation
of multipole rates for any level having an external shell l ≠q 0 .
---------------------------------------------------------
Title: The Frequency of Carbon-enhanced Metal-poor Stars in the
Galaxy from the HERES Sample
Authors: Lucatello, Sara; Beers, Timothy C.; Christlieb, Norbert;
Barklem, Paul S.; Rossi, Silvia; Marsteller, Brian; Sivarani,
Thirupathi; Lee, Young Sun
2006ApJ...652L..37L Altcode: 2006astro.ph..9730L
We estimate the frequency of carbon-enhanced metal-poor (CEMP) stars
among very metal-poor stars, based on an analysis of 349 stars with
available high-resolution spectra observed as part of the Hamburg/ESO
R-process Enhanced Star (HERES) survey. We obtain that a lower limit of
21%+/-2% of stars with [Fe/H] <=-2.0 exhibit [C/Fe] >=+1.0. These
fractions are higher than those that have been reported by recent
examinations of this question, based on substantially smaller samples
of stars. We discuss the source of this difference and suggest that in
order to take into account effects that result in a decrease of surface
carbon abundance with advancing evolution, a definition of CEMP stars
based on a [C/Fe] cutoff that varies as a function of luminosity is
more appropriate. We discuss the likely occurrence of dilution and
mixing for many CEMP stars, which, if properly accounted for, would
increase this fraction still further.
---------------------------------------------------------
Title: New Abundances for Old Stars - Atomic Diffusion at Work in
NGC 6397
Authors: Korn, A.; Grundahl, F.; Richard, O.; Barklem, P.; Mashonkina,
L.; Collet, R.; Piskunov, N.; Gustafsson, B.
2006Msngr.125....6K Altcode: 2006astro.ph.10077K; 2006Msngr.125...10K
A homogeneous spectroscopic analysis of unevolved and evolved
stars in the metal-poor globular cluster NGC 6397 with FLAMES-UVES
reveals systematic trends of stellar surface abundances that are
likely caused by atomic diffusion. This finding helps to understand,
among other issues, why the lithium abundances of old halo stars are
significantly lower than the abundance found to be produced shortly
after the Big Bang.
---------------------------------------------------------
Title: A probable stellar solution to the cosmological lithium
discrepancy
Authors: Korn, A. J.; Grundahl, F.; Richard, O.; Barklem, P. S.;
Mashonkina, L.; Collet, R.; Piskunov, N.; Gustafsson, B.
2006Natur.442..657K Altcode: 2006astro.ph..8201K
The measurement of the cosmic microwave background has strongly
constrained the cosmological parameters of the Universe. When the
measured density of baryons (ordinary matter) is combined with
standard Big Bang nucleosynthesis calculations, the amounts of
hydrogen, helium and lithium produced shortly after the Big Bang can
be predicted with unprecedented precision. The predicted primordial
lithium abundance is a factor of two to three higher than the value
measured in the atmospheres of old stars. With estimated errors of 10
to 25%, this cosmological lithium discrepancy seriously challenges
our understanding of stellar physics, Big Bang nucleosynthesis or
both. Certain modifications to nucleosynthesis have been proposed,
but found experimentally not to be viable. Diffusion theory, however,
predicts atmospheric abundances of stars to vary with time, which offers
a possible explanation of the discrepancy. Here we report spectroscopic
observations of stars in the metal-poor globular cluster NGC6397
that reveal trends of atmospheric abundance with evolutionary stage
for various elements. These element-specific trends are reproduced
by stellar-evolution models with diffusion and turbulent mixing. We
thus conclude that diffusion is predominantly responsible for the low
apparent stellar lithium abundance in the atmospheres of old stars by
transporting the lithium deep into the star.
---------------------------------------------------------
Title: An abundance study of the most iron-poor star HE1327-2326
with Subaru/HDS
Authors: Aoki, W.; Frebel, A.; Christlieb, N.; Norris, J. E.; Beers,
T. C.; Minezaki, T.; Barklem, P. S.; Honda, S.; Takada-Hidai, M.;
Asplund, M.; Ryan, S. G.; Tsangarides, S.; Eriksson, K.; Steinhauer,
A.; Deliyannis, C. P.; Nomoto, K.; Fujimoto, M. Y.; Ando, H.; Yoshii,
Y.; Kajino, T.
2006AIPC..847...53A Altcode:
We present an elemental abundance analysis of HE 1327-2326, the most
iron-deficient star known, based on a comprehensive investigation of
spectra obtained with the Subaru Telescope. HE 1327-2326 is either
in its main sequence or subgiant phase of evolution, hence it is
essentially unevolved. The chemical abundances of this star have
the following properties, which provide new constraints on models of
nucleosynthesis processes that occurred in first-generation objects: <P
/>(1)The iron abundance (NLTE) is [Fe/H]= -5.45. This value is 0.2 dex
lower than that of HE 0107-5240, the previously most iron-poor object
known. No object having [Fe/H]= -5 ~ -4 is known to date. <P />(2)This
star, as well as HE 0107-5240, exhibits extremely large overabundances
of carbon relative to solar ratios ([C/Fe]~ +4). <P />(3)HE 1327-2326
exhibits remarkable overabundances of the light elements (N, Na, Mg
and Al), while HE 0107-5240 shows only relatively small excesses of N
and Na. <P />(4)A large overabundance of Sr is found in HE 1327-2326
as compared to other extremely low metallicity stars. <P />(5)The Li
I 6707 Å line, which is detected in the great majority of metal-poor
dwarfs and warm subgiants, is not found in HE 1327-2326. The upper
limit on the Li abundance we determine (log ɛ (Li) < 1.5) is
clearly lower than the expected value from the Spite plateau.
---------------------------------------------------------
Title: VizieR Online Data Catalog: HERES II. Spectroscopic analysis
(Barklem+, 2005)
Authors: Barklem, P. S.; Christlieb, N.; Beers, T. C.; Hill, V.;
Bessell, M. S.; Holmberg, J.; Marsteller, B.; Rossi, S.; Zickgraf,
F. -J.; Reimers, D.
2006yCat..34390129B Altcode:
The spectra are analysed using an automated line profile analysis
method based on the Spectroscopy Made Easy (SME) codes of Valenti &
Piskunov (1996A&AS..118..595V). Elemental abundances of moderate
precision (absolute rms errors of order 0.25dex, relative rms errors of
order 0.15dex) have been obtained for 22 elements, C, Mg, Al, Ca, Sc,
Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu,
where detectable. Of these elements, 14 are usually detectable at the
3sigma confidence level for our typical spectra. The remainder can be
detected in the least metal-poor stars of the sample, spectra with
higher than average S/N, or when the abundance is enhanced. <P />(3
data files).
---------------------------------------------------------
Title: The Hamburg/ESO R-process enhanced star survey (HERES). III. HE
0338-3945 and the formation of the r + s stars
Authors: Jonsell, K.; Barklem, P. S.; Gustafsson, B.; Christlieb,
N.; Hill, V.; Beers, T. C.; Holmberg, J.
2006A&A...451..651J Altcode: 2006astro.ph..1476J
We have derived abundances of 33 elements and upper limits for 6
additional elements for the metal-poor ([Fe/H] = -2.42) turn-off star
HE 0338-3945 from high-quality VLT-UVES spectra. The star is heavily
enriched, by about a factor of 100 relative to iron and the Sun, in the
heavy s-elements (Ba, La, ...). It is also heavily enriched in Eu, which
is generally considered an r-element, and in other similar elements. It
is less enriched, by about a factor of 10, in the lighter s-elements
(Sr, Y and Zr). C is also strongly enhanced and, to a somewhat lesser
degree, N and O. These abundance estimates are subject to severe
uncertainties due to NLTE and thermal inhomogeneities which are not
taken into detailed consideration. However, an interesting result,
which is most probably robust in spite of these uncertainties, emerges:
the abundances derived for this star are very similar to those of
other stars with an overall enhancement of all elements beyond the iron
peak. We have defined criteria for this class of stars, r+s stars, and
discuss nine different scenarios to explain their origin. None of these
explanations is found to be entirely convincing. The most plausible
hypotheses involve a binary system in which the primary component goes
through its giant branch and asymptotic giant branch phases and produces
CNO and s-elements which are dumped onto the observed star. Whether
the r-element Eu is produced by supernovae before the star was formed
(perhaps triggering the formation of a low-mass binary), by a companion
as it explodes as a supernova (possibly triggered by mass transfer),
or whether it is possibly produced in a high-neutron-density version
of the s-process is still unclear. Several suggestions are made on
how to clarify this situation.
---------------------------------------------------------
Title: HE 1327-2326, an Unevolved Star with [Fe/H]<-5.0. I. A
Comprehensive Abundance Analysis
Authors: Aoki, W.; Frebel, A.; Christlieb, N.; Norris, J. E.; Beers,
T. C.; Minezaki, T.; Barklem, P. S.; Honda, S.; Takada-Hidai, M.;
Asplund, M.; Ryan, S. G.; Tsangarides, S.; Eriksson, K.; Steinhauer,
A.; Deliyannis, C. P.; Nomoto, K.; Fujimoto, M. Y.; Ando, H.; Yoshii,
Y.; Kajino, T.
2006ApJ...639..897A Altcode: 2005astro.ph..9206A
We present the elemental abundances of HE 1327-2326, the most
iron-deficient star known, determined from a comprehensive analysis
of spectra obtained with the Subaru Telescope High Dispersion
Spectrograph. HE 1327-2326 is either in its main-sequence or
subgiant phase of evolution. Its non-LTE-corrected iron abundance is
[Fe/H]=-5.45, 0.2 dex lower than that of HE 0107-5240, the previously
most iron-poor object known, and more than 1 dex lower than those
of all other metal-poor stars. Both HE 1327-2326 and HE 0107-5240
exhibit extremely large overabundances of carbon ([C/Fe]~+4). The
combination of extremely high carbon abundance with outstandingly
low iron abundance in these objects clearly distinguishes them from
other metal-poor stars. The large carbon excesses in these two stars
are not the result of a selection effect. There also exist important
differences between HE 1327-2326 and HE 0107-5240. While the former
shows remarkable overabundances of the light elements (N, Na, Mg,
and Al), the latter shows only relatively small excesses of N and
Na. The neutron-capture element Sr is detected in HE 1327-2326,
but not in HE 0107-5240 its Sr abundance is significantly higher
than the upper limit for HE 0107-5240. The Li I λ6707 line, which is
detected in most metal-poor dwarfs and warm subgiants having the same
temperature as HE 1327-2326, is not found in this object. The upper
limit of its Li abundance [logɛ(Li)<1.5] is clearly lower than the
Spite plateau value. These data provide new constraints on models of
nucleosynthesis processes in the first-generation objects that were
responsible for metal enrichment at the earliest times. We discuss
possible scenarios to explain the observed abundance patterns. <P
/>Based on data collected with the Subaru Telescope, which is operated
by the National Astronomical Observatory of Japan.
---------------------------------------------------------
Title: Pinning Down Gravitational Settling
Authors: Korn, A. J.; Piskunov, N.; Grundahl, F.; Barklem, P.;
Gustafsson, B.
2006cams.book..294K Altcode: 2006astro.ph..8338K
We analyse high-resolution archival UVES data of turnoff
and subgiant stars in the nearby globular cluster NGC6397
([Fe/H]≈-2). Balmer-profile analyses are performed to derive
reddening-free effective temperatures. Due to the limited S/N and
uncertainties related to blaze removal, we find the data quality
insufficient to exclude the existence of gravitational settling. If
the newly derived effective temperatures are taken as a basis for an
abundance analysis, the photospheric iron (Fe ii) abundance in the
turnoff stars is 0.11 dex lower than in the (well-mixed) subgiants.
---------------------------------------------------------
Title: The frequency of Carbon-enhanced stars in HERES and SDSS
Authors: Beers, Timothy C.; Lucatello, Sara; Marsteller, Brian;
Sivarani, Thirupathi; Barklem, Paul; Christlieb, Norbert; Rossi, Silvia
2006isna.confE..17B Altcode: 2006PoS....28E..17B
Recent large surveys of metal-poor stars in the Galaxy have revealed
that a surprising fraction are enhanced in their carbon-to-iron ratios
by factors of 10-10,000 relative to the solar ratio. Although the
carbon overabundances in most of the stars in the metallicity interval
-2.7 ≤ [Fe/H] ≤ -2.0 are likely to have arisen from Asymptotic
Giant Branch processing (and subsequent dumping via mass transfer to
a surviving companion), there exist many stars with [Fe/H] < -3.0
(including the two lowest [Fe/H] stars known, with [Fe/H] < -5.0)
that may not be accounted for by this process. Rather, primordial (or
nearly primordial) progenitors are implicated. We report on the existing
information from present surveys, including cool giants from the re-
cently completed HERES (Hamburg/ESO R-process Enhanced Star) survey,
and from warm main-sequence turnoff stars selected from SDSS-I. We also
describe the results that will come from the recently-funded extension
of the SDSS, which includes the program SEGUE: Sloan Ex- tension for
Galactic Understanding and Exploration. SEGUE will identify some 20,000
stars with [Fe/H] < -2.0, several thousand of which are expected
to be carbon enhanced.
---------------------------------------------------------
Title: Spin depolarizing effect in collisions of simple/complex
atoms in spherically symmetric states with neutral hydrogen
Authors: Derouich, M.; Barklem, P. S.; Sahal-Bréchot, S.
2005A&A...441..395D Altcode:
We present a general semi-classical treatment of the depolarization
of spherically symmetric states (i.e. s-states) which necessarily
accounts for the exchange interaction via exchange perturbation
theory. Calculations of the destruction rate of orientation of general
s-states, characterized by their effective principal quantum number n^*,
due to isotropic collisions with neutral hydrogen have been carried
out. It is found that the behaviour of the depolarization rates
with n<SUP>*</SUP> obeys a power law. We express the depolarization
and polarization transfer rates of complex atoms in terms of the
depolarization rates of simple atoms. These results are used to infer
the all non-zero depolarization and polarization transfer rates of the
lower levels of the multiplets 42 and 145 of neutral Ti I. Further, we
explain how our results can be used to easily calculate the hyperfine
depolarization and polarization transfer rates. In order to validate our
general theory, we have computed the destruction rate of orientation
of the ground levels of the alkali metals Li I, Na I, K I, Rb I and
Cs I using the quantum chemistry potentials of Geum et al. (2001,
J. Ch. Phys., 115, 5984), employing our semi-classical description of
the collision dynamics. For Na I ground state, the percentage error
on our destruction rate of the orientation with respect to the fully
quantal rate of Kerkeni et al. (2000b, A&A, 364, 937; note Erratum)
is less than 1% at T=5000 K.
---------------------------------------------------------
Title: The Hamburg/ESO R-process enhanced star survey
(HERES). II. Spectroscopic analysis of the survey sample
Authors: Barklem, P. S.; Christlieb, N.; Beers, T. C.; Hill, V.;
Bessell, M. S.; Holmberg, J.; Marsteller, B.; Rossi, S.; Zickgraf,
F. -J.; Reimers, D.
2005A&A...439..129B Altcode: 2005astro.ph..5050B
We present the results of analysis of "snapshot" spectra of 253
metal-poor halo stars -3.8≤ [Fe/H] ≤ -1.5 obtained in the HERES
survey. The snapshot spectra have been obtained with VLT/UVES and have
typically S/N∼ 54 per pixel (ranging from 17 to 308), R∼20 000, λ
= 3760-4980 Å. This sample represents the major part of the complete
HERES sample of 373 stars; however, the CH strong content of the sample
is not dealt with here. The spectra are analysed using an automated line
profile analysis method based on the Spectroscopy Made Easy (SME) codes
of Valenti & Piskunov. Elemental abundances of moderate precision
(absolute rms errors of order 0.25 dex, relative rms errors of order
0.15 dex) have been obtained for 22 elements, C, Mg, Al, Ca, Sc, Ti,
V, Cr, Mn, Fe, Co, Ni, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu,
where detectable. Of these elements, 14 are usually detectable at
the 3σ confidence level for our typical spectra. The remainder can
be detected in the least metal-poor stars of the sample, spectra with
higher than average S/N, or when the abundance is enhanced. Among the
sample of 253 stars, disregarding four previously known comparison
stars, we find 8 r-II stars and 35 r-I stars. The r-II stars, including
the two previously known examples CS 22892-052 and CS 31082-001, are
centred on a metallicity of [Fe/H] = -2.81, with a very small scatter,
on the order of 0.16 dex. The r-I stars are found across practically
the entire metallicity range of our sample. We also find three stars
with strong enhancements of Eu which are s-process rich. A significant
number of new very metal-poor stars are confirmed: 49 stars with
[Fe/H]<-3 and 181 stars with -3<[Fe/H]<-2. We find one star
with [Fe/H]<-3.5. We find the scatter in the abundance ratios of
Mg, Ca, Sc, Ti, Cr, Fe, Co, and Ni, with respect to Fe and Mg, to be
similar to the estimated relative errors and thus the cosmic scatter
to be small, perhaps even non-existent. The elements C, Sr, Y, Ba
and Eu, and perhaps Zr, show scatter at [Fe/H] ⪉ -2.5 significantly
larger than can be explained from the errors in the analysis, implying
scatter which is cosmic in origin. Significant scatter is observed in
abundance ratios between light and heavy neutron-capture elements at
low metallicity and low levels of r-process enrichment.
---------------------------------------------------------
Title: Efficient Searches for r-Process-Enhanced, Metal-Poor Stars
Authors: Beers, T. C.; Barklem, P. S.; Christlieb, N.; Hill, V.
2005NuPhA.758..595B Altcode: 2004astro.ph..8381B
Neutron-capture-enhanced, metal-poor stars are of central importance
to developing an understanding of the operation of the r-process
in the early Galaxy, thought to be responsible for the formation
of roughly half of all elements beyond the iron peak. A handful
of neutron-capture-rich, metal-poor stars with [Fe/H]<-2.0 have
already been identified, including the well known r-process-enhanced
stars CS 22892-052 and CS 31082-001. However, many questions of
fundamental interest can only be addressed with the assemblage of
a much larger sample of such stars, so that general properties can
be distinguished. We describe a new effort, HERES: The Hamburg/ESO
R-Process-Enhanced Star survey, nearing completion, which will identify
on the order of 5 10 additional highly r-process-enhanced, metal-poor
stars, and in all likelihood, a similar or greater number of mildly
r-process-enhanced, metal-poor stars in the halo of the Galaxy. HERES
is based on rapid “snapshot” spectra of over 350 candidate halo
giants with [Fe/H]<-2.0, obtained at moderately high resolution,
and with moderate signal-to-noise ratios, using the UVES spectrograph
on the European VLT 8m telescope.
---------------------------------------------------------
Title: The broadening of Fe II lines by neutral hydrogen collisions
Authors: Barklem, P. S.; Aspelund-Johansson, J.
2005A&A...435..373B Altcode: 2005astro.ph..2098B
Data for the broadening of 24188 Fe II lines by collisions with neutral
hydrogen atoms have been computed using the theory of Anstee &
O'Mara as extended to singly ionised species and higher orbital angular
momentum states by Barklem & O'Mara. Data have been computed for
all Fe II lines between observed energy levels in the line lists of
Kurucz with log gf > -5 for which the theory is applicable. The
variable energy debt parameter E<SUB>p</SUB> used in computing the
second order perturbation theory potential is chosen to be consistent
with the long range dispersion interaction constant C<SUB>6</SUB>
computed using the f-values from Kurucz.
---------------------------------------------------------
Title: Collisional depolarization of the lines of complex atoms/ions
by neutral hydrogen
Authors: Derouich, M.; Sahal-Bréchot, S.; Barklem, P. S.
2005A&A...434..779D Altcode:
We have developed a new semi-classical method for calculating the
depolarization and polarization transfer rates of spectral lines of
neutral and ionised atoms by collisions with atomic hydrogen (Derouich
et al. 2003a, A&A, 404, 763; 2003b, A&A, 409, 369; <P />2004a,
A&A, 414, 369; 2004b, A&A, 426, 707). <P />Up to now, our
depolarization <P />rate calculations have been limited to simple
atoms. In the present paper, we extend our theory to more complex
atoms and we apply our new results to provide the first calculations
associated <P />with the upper levels of multiplet 145 of neutral
titanium Ti I which constitutes a remarkable example of the second
solar spectrum (Manso Sainz & Landi Degl'Innocenti 2002, A&A,
394, 1093).
---------------------------------------------------------
Title: Nucleosynthetic signatures of the first stars
Authors: Frebel, Anna; Aoki, Wako; Christlieb, Norbert; Ando, Hiroyasu;
Asplund, Martin; Barklem, Paul S.; Beers, Timothy C.; Eriksson,
Kjell; Fechner, Cora; Fujimoto, Masayuki Y.; Honda, Satoshi; Kajino,
Toshitaka; Minezaki, Takeo; Nomoto, Ken'ichi; Norris, John E.; Ryan,
Sean G.; Takada-Hidai, Masahide; Tsangarides, Stelios; Yoshii, Yuzuru
2005Natur.434..871F Altcode: 2005astro.ph..3021F
The chemically most primitive stars provide constraints on the nature
of the first stellar objects that formed in the Universe; elements
other than hydrogen, helium and traces of lithium present within
these objects were generated by nucleosynthesis in the very first
stars. The relative abundances of elements in the surviving primitive
stars reflect the masses of the first stars, because the pathways of
nucleosynthesis are quite sensitive to stellar masses. Several models
have been suggested to explain the origin of the abundance pattern
of the giant star HE0107-5240, which hitherto exhibited the highest
deficiency of heavy elements known. Here we report the discovery of
HE1327-2326, a subgiant or main-sequence star with an iron abundance
about a factor of two lower than that of HE0107-5240. Both stars
show extreme overabundances of carbon and nitrogen with respect to
iron, suggesting a similar origin of the abundance patterns. The
unexpectedly low Li and high Sr abundances of HE1327-2326, however,
challenge existing theoretical understanding: no model predicts the
high Sr abundance or provides a Li depletion mechanism consistent with
data available for the most metal-poor stars.
---------------------------------------------------------
Title: Metal-poor star abundances from the HERES project
Authors: Barklem, P. S.; Christlieb, N.; Beers, T. C.
2005ESASP.560..433B Altcode: 2005csss...13..433B
No abstract at ADS
---------------------------------------------------------
Title: VizieR Online Data Catalog: Broadening of Fe II lines by H
collisions (Barklem+, 2005)
Authors: Barklem, P. S.; Aspelund-Johansson, J.
2005yCat..34350373B Altcode:
The file table1.dat lists the computed interaction constants along
with relevant input data for all levels of Fe II considered. The
file table2.dat lists the line broadening data along with sufficient
information to uniquely identify each line. <P />(2 data files).
---------------------------------------------------------
Title: HERES: The search for r-process enhanced, metal-poor stars
Authors: Beers, T. C.; Chistlieb, N.; Bessell, M. S.; Hill, V.;
Barklem, P. S.; Ryan, S. G.; Rossi, S.; Korn, A.
2005HiA....13S.579B Altcode:
In recent years a handful of extremely metal-deficient stars have
been identified that exhibit moderate to large enhancements of their
abundance ratios (relative to Fe) of elements associated with the
astrophysical r-process enabling detections of radioactive species such
as U and Th. Our understanding could be greatly improved by increasing
the numbers of known r-process-enhanced metal-poor stars as well from
building the sample to the point where meaningful measures of the
frequency of the phenomenon especially as a function of metallicity
could be ascertained. <P />We describe the present status of HERES --
The Hamburg/ESO R-process Enhanced Star survey. This survey is based
upon ""snapshot"" high-resolution VLT/UVES spectra of large numbers
of giants with [Fe/H] < -2.5. Spectra of sufficient quality
to detect the presence of the EuII line (4019 A) a distinctive
neutron-capture feature have now been obtained for some 150-200
extremely metal-deficient giants chosen from the Hamburg/ESO survey. We
discuss the number of moderate- and highly r-process enhanced stars
discovered update our estimate of the frequency of their detection and
present a discussion of the distribution of ~ 20 other easily measured
elements in each of these stars (e.g. C Ca Mg Si Co Ni Sr Ba etc.).
---------------------------------------------------------
Title: The new record holder for the most iron-poor star: HE 1327
2326, a dwarf or subgiant with [Fe/H[=[minus sign]5.4
Authors: Frebel, A.; Aoki, W.; Christlieb, N.; Ando, H.; Asplund, M.;
Barklem, P. S.; Beers, T. C.; Eriksson, K.; Fechner, C.; Fujimoto,
M. Y.; Honda, S.; Kajino, T.; Minezaki, T.; Nomoto, K.; Norris, J. E.;
Ryan, S. G.; Takada-Hidai, M.; Tsangarides, S.; Yoshii, Y.
2005IAUS..228..207F Altcode: 2005astro.ph..9658F
We describe the discovery of HE 1327-2326, a dwarf or subgiant with
[Fe/H]=-5.4. The star was found in a sample of bright metal-poor
stars selected from the Hamburg/ESO survey. Its abundance pattern is
characterized by very high C and N abundances. The detection of Sr
which is overabundant by a factor of 10 as compared to iron and the
Sun, suggests that neutron-capture elements had already been produced
in the very early Galaxy. A puzzling Li depletion is observed in this
unevolved star which contradicts the value of the primordial Li derived
from WMAP and other Li studies. Possible scenarios for the origin of
the abundance pattern (Pop. II or Pop. III) are presented as well as
an outlook on future observations.
---------------------------------------------------------
Title: The Hamburg/ESO R-process Enhanced Star survey (HERES):
Project Overview, and New r-II Stars
Authors: Christlieb, N.; Beers, T. C.; Barklem, P. S.; Bessell, M. S.;
Hill, V.; Holmberg, J.; Korn, A. J.; Marsteller, B.; Mashonkina, L.;
Rossi, S.; Zickgraf, F. -J.; Kratz, K. -L.; Nordström, B.; Pfeiffer,
B.; Rhee, J.; Ryan, S. G.
2005IAUS..228..439C Altcode:
We report on a dedicated effort to identify and study metal-poor stars
that are strongly enhanced in r-process elements ([r/Fe]>+1.0dex;
hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey
(HERES). In a sample of 253 confirmed metal-poor stars for which
"snapshot" spectra (R∼ 20,000; S/N ∼ 50/1 per pixel) were obtained
with VLT/UVES, and abundances were determined in an automated fashion
using the methods of Barklem et al. (2005), we identified eight new
r-II stars. They are now being studied in detail by means of higher
resolution and S/N spectroscopy. The new r-II stars have metallicities
in the range -3.2. Future searches for r-II stars should therefore focus
on stars in this [Fe/H] range. Moderately r-process enhanced stars
(i.e., +0.3 dex; r-I stars) were found at metallicities as high as
[Fe/H] = -1.5. The [Fe/H] ranges in which r-I and r-II stars can be
found may provide an important constraint for the identification of
the site(s) of the r-process(es).
---------------------------------------------------------
Title: The Hamburg/ESO R-process Enhanced Star survey (HERES):
Abundances
Authors: Barklem, P. S.; Christlieb, N.; Beers, T. C.; Hill, V.;
Holmberg, J.; Marsteller, B.; Rossi, S.; Zickgraf, F. -J.; Bessell,
M. S.
2005IAUS..228..201B Altcode:
We present the results of analysis of "snapshot" spectra (i.e., R=20,000
and S/N=50 per pixel) of 253 metal-poor halo stars -3.8[Fe/H] obtained
in the HERES survey. The spectra are analysed using an automated
line profile analysis method based on the Spectroscopy Made Easy
(SME) codes of Valenti & Piskunov (1996). Elemental abundances of
moderate precision (absolute r.m.s. errors of order 0.25 dex) have been
obtained for 22 elements, C, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co,
Ni, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu, where detectable. The
results are presented and discussed, particularly trends and scatter
in the abundance distributions.
---------------------------------------------------------
Title: The Hamburg/ESO R-process Enhanced Star survey (HERES).
I. Project description, and discovery of two stars with strong
enhancements of neutron-capture elements
Authors: Christlieb, N.; Beers, T. C.; Barklem, P. S.; Bessell, M.;
Hill, V.; Holmberg, J.; Korn, A. J.; Marsteller, B.; Mashonkina, L.;
Qian, Y. -Z.; Rossi, S.; Wasserburg, G. J.; Zickgraf, F. -J.; Kratz,
K. -L.; Nordström, B.; Pfeiffer, B.; Rhee, J.; Ryan, S. G.
2004A&A...428.1027C Altcode: 2004astro.ph..8389C
We report on a dedicated effort to identify and study metal-poor
stars strongly enhanced in r-process elements ([r/Fe]>1 dex;
hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey
(HERES). Moderate-resolution (∼2 Å) follow-up spectroscopy has
been obtained for metal-poor giant candidates selected from the
Hamburg/ESO objective-prism survey (HES) as well as the HK survey to
identify sharp-lined stars with [Fe/H]<-2.5 dex. For several hundred
confirmed metal-poor giants brighter than B∼ 16.5 mag (most of them
from the HES), “snapshot” spectra (R∼ 20 000; S/N ∼ 30 per pixel)
are being obtained with VLT/UVES, with the main aim of finding the 2-3%
r-II stars expected to be among them. These are studied in detail by
means of higher resolution and higher S/N spectra. In this paper we
describe a pilot study based on a set of 35 stars, including 23 from the
HK survey, eight from the HES, and four comparison stars. We discovered
two new r-II stars, CS 29497-004 ([Eu/Fe]=1.64± 0.22) and CS 29491-069
([Eu/Fe]=1.08± 0.23). A first abundance analysis of CS 29497-004 yields
that its abundances of Ba to Dy are on average enhanced by 1.5 dex with
respect to iron and the Sun and match a scaled solar r-process pattern
well, while Th is underabundant relative to that pattern by 0.3 dex,
which we attribute to radioactive decay. That is, CS 29497-004 seems
not to belong to the class of r-process enhanced stars displaying
an “actinide boost”, like CS 31082-001 (Hill et al. 2002), or CS
30306-132 (Honda et al. 2004b). The abundance pattern agrees well with
predictions of the phenomenological model of Qian & Wasserburg. <P
/>Based in large part on observations collected at the European Southern
Observatory, Paranal, Chile (proposal number 68.B-0320).}
---------------------------------------------------------
Title: Collisional depolarization and transfer rates of spectral
lines by atomic hydrogen. IV. Application to ionised atoms
Authors: Derouich, M.; Sahal-Bréchot, S.; Barklem, P. S.
2004A&A...426..707D Altcode: 2004astro.ph..1642D
The semi-classical theory of collisional depolarization of spectral
lines that we have applied to neutral atoms in previous papers
is extended to spectral lines of singly ionised atoms. In order to
validate our general theory, we compare our results to quantum chemistry
calculations obtained for the particular cases of the 3d <SUP>2</SUP>D
and 4p <SUP>2</SUP>P states of the CaII ion. As a demonstration of
the universality of our theory and the easiness of its application,
we calculate depolarization and polarization transfer rates for the
5p <SUP>2</SUP>P state of the SrII ion. Analytical expressions of all
rates as a function of local temperature are given. Our results for
the CaII ion are compared to recent quantum chemistry calculations. A
discussion of our results is presented.
---------------------------------------------------------
Title: Efficient Searches for r-Process-Enhanced Metal-Poor Stars
Authors: Beers, T. C.; Christlieb, N.; Barklem, P. S.
2004rpao.conf..109B Altcode:
We describe the motivation and execution plan for HERES: The Hamburg/ESO
R-process-Enhanced Star survey, an onging effort to significantly
increase the numbers of known metal-poor stars with highly elevated
ratios of their r-process elements, similar to the first few stars
of this class, CS 22892-052 and CS 31082-001. Such stars provide the
best available probes of the operation of the astrophysical r-process,
the opportunity to constrain the site(s) in which it occurs, and for
exploration of the applicability of cosmo-chronometers, such as obtained
from Eu/Th and U/Th. We outline a number of the important questions
that need to be considered in order for progress to be made. First
results from HERES should be available by the time this contribution
appears in print.
---------------------------------------------------------
Title: S<SUP>4</SUP>N: A spectroscopic survey of stars in the solar
neighborhood. The Nearest 15 pc
Authors: Allende Prieto, C.; Barklem, P. S.; Lambert, D. L.; Cunha, K.
2004A&A...420..183A Altcode: 2004astro.ph..3108P; 2004astro.ph..3108A
We report the results of a high-resolution spectroscopic survey of all
the stars more luminous than M_V = 6.5 mag within 14.5 pc from the
Sun. The Hipparcos catalog's completeness limits guarantee that our
survey is comprehensive and free from some of the selection effects in
other samples of nearby stars. The resulting spectroscopic database,
which we have made publicly available, includes spectra for 118 stars
obtained with a resolving power of R ≃ 50 000, continuous spectral
coverage between ∼ 362-921 nm, and typical signal-to-noise ratios
in the range 150-600. We derive stellar parameters and perform a
preliminary abundance and kinematic analysis of the F-G-K stars
in the sample. The inferred metallicity ([Fe/H]) distribution is
centered at about -0.1 dex, and shows a standard deviation of 0.2
dex. A comparison with larger samples of Hipparcos stars, some of
which have been part of previous abundance studies, suggests that
our limited sample is representative of a larger volume of the local
thin disk. We identify a number of metal-rich K-type stars which
appear to be very old, confirming the claims for the existence of
such stars in the solar neighborhood. With atmospheric effective
temperatures and gravities derived independently of the spectra, we
find that our classical LTE model-atmosphere analysis of metal-rich
(and mainly K-type) stars provides discrepant abundances from neutral
and ionized lines of several metals. This ionization imbalance could
be a sign of departures from LTE or inhomogeneous structure, which
are ignored in the interpretation of the spectra. Alternatively,
but seemingly unlikely, the mismatch could be explained by systematic
errors in the scale of effective temperatures. Based on transitions of
majority species, we discuss abundances of 16 chemical elements. In
agreement with earlier studies we find that the abundance ratios to
iron of Si, Sc, Ti, Co, and Zn become smaller as the iron abundance
increases until approaching the solar values, but the trends reverse
for higher iron abundances. At any given metallicity, stars with a low
galactic rotational velocity tend to have high abundances of Mg, Si,
Ca, Sc, Ti, Co, Zn, and Eu, but low abundances of Ba, Ce, and Nd. The
Sun appears deficient by roughly 0.1 dex in O, Si, Ca, Sc, Ti, Y,
Ce, Nd, and Eu, compared to its immediate neighbors with similar iron
abundances. <P />Based on observations made with the 2.7 m telescope at
the McDonald Observatory of the University of Texas at Austin (Texas),
and the 1.52 m telescope at the European Southern Observatory (La
Silla, Chile) under the agreement with the CNPq/Observatorio Nacional
(Brazil). <P />Tables 3-5 are only available in electronic form at
the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or
via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/420/183
---------------------------------------------------------
Title: HE 0107-5240, a Chemically Ancient Star. I. A Detailed
Abundance Analysis
Authors: Christlieb, N.; Gustafsson, B.; Korn, A. J.; Barklem, P. S.;
Beers, T. C.; Bessell, M. S.; Karlsson, T.; Mizuno-Wiedner, M.
2004ApJ...603..708C Altcode: 2003astro.ph.11173C
We report on a detailed abundance analysis of HE 0107-5240, a halo giant
with [Fe/H]<SUB>NLTE</SUB>=-5.3. This star was discovered in the course
of follow-up medium-resolution spectroscopy of extremely metal-poor
candidates selected from the digitized Hamburg/ESO objective-prism
survey. On the basis of high-resolution VLT/UVES spectra, we derive
abundances for eight elements (C, N, Na, Mg, Ca, Ti, Fe, and Ni)
and upper limits for another 12 elements. A plane-parallel LTE model
atmosphere has been specifically tailored for the chemical composition
of HE 0107-5240. Scenarios of the origin of the abundance pattern
observed in the star are discussed. We argue that HE 0107-5240 is
most likely not a post-asymptotic giant branch star and that the
extremely low abundances of the iron-peak and other elements are
not due to selective dust depletion. The abundance pattern of HE
0107-5240 can be explained by preenrichment from a zero-metallicity
Type II supernova (SN II) of 20-25 M<SUB>solar</SUB>, plus either
self-enrichment with C and N or production of these elements in the
asymptotic giant branch phase of a formerly more massive companion,
which is now a white dwarf. However, significant radial velocity
variations have not been detected within the 52 days covered by our
moderate- and high-resolution spectra. Alternatively, the abundance
pattern can be explained by enrichment of the gas cloud from which
HE 0107-5240 formed by a 25 M<SUB>solar</SUB> first-generation
star exploding as a subluminous SN II, as proposed by Umeda &
Nomoto. We discuss consequences of the existence of HE 0107-5240 for
low-mass star formation in extremely metal-poor environments and for
currently ongoing and future searches for the most metal-poor stars
in the Galaxy. <P />Based on observations collected at the European
Southern Observatory, Paranal, Chile (proposal 268.D-5745).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Spectroscopic survey in solar
neighborhood (Allende Prieto+ 2004)
Authors: Allende Prieto, C.; Barklem, P. S.; Lambert, D. L.; Cunha, K.
2004yCat..34200183A Altcode:
Tables with kinematic data and chemical abundances for the sample. The
atomic line data are also provided. The data in FITS are available
in the internet from the project site S4N (Spectrsocopic Survey of
Stars in the Solar Neighborhood) at http://hebe.as.utexas.edu/s4n/
and at its mirror http://www.astro.uu.se/~s4n/ <P />(5 data files).
---------------------------------------------------------
Title: Collisional broadening of Mg, Sr, Ca and Na resonance lines
by atomic hydrogen
Authors: Kerkeni, B.; Barklem, P. S.; Spielfiedel, A.; Feautrier, N.
2004JPhB...37..677K Altcode:
This paper compares different approaches used in the calculation of
the broadening of spectral lines by H-atom collisions. Firstly, the
validity of the semi-classical approach for the collision versus the
quantum one is discussed. It is shown that, at the temperatures typical
of stellar atmospheres (from 3000 to 10 000 K), a classical approach
(with the advantage of reduced computation times) is sufficient. The
dependence of the broadening constants on interatomic potentials is also
studied. Two different approaches were used to derive these potentials:
in the first approach, the interaction energy is determined by the
usual methods of quantum chemistry. The second approach, developed by
Anstee, Barklem and O'Mara (ABO potentials), is based on second-order
perturbation theory. In the case of Mg H, a hybrid potential obtained
from ab initio values for the short distances and from the perturbation
method in the asymptotic region was also tested. The results for the Na
resonance line show that even significant differences in the potentials
lead to relatively small changes in the calculated widths. From the
comparison of the results for the Mg, Sr and Ca resonance lines, it
appears that ABO potentials give results of the order of 8 20% smaller
than results from ab initio and hybrid potentials. This difference is
attributed to the presence of an avoided ionic crossing in the upper
singlet Sgr states that coincides roughly with the Weisskopf radius.
---------------------------------------------------------
Title: On the collisional depolarization and transfer rates of
spectral lines by atomic hydrogen. III. Application to f-states of
neutral atoms
Authors: Derouich, M.; Sahal-Bréchot, S.; Barklem, P. S.
2004A&A...414..373D Altcode: 2003astro.ph..7553D
The theory of collisional depolarization of spectral lines by atomic
hydrogen (Derouich et al. 2003a; Derouich et al. 2003b) is extended to
f-atomic levels (l=3). Depolarization rates, polarization and population
transfer rates are calculated and results are given. Each cross section
as a function of the effective quantum number for a relative velocity
of 10 km s<SUP>-1</SUP> is given together with an exponent łambda,
if it exists, with the assumption that the cross section varies with
velocity as v<SUP>-λ</SUP>. The general trends of depolarization rates,
polarization transfer rates and population transfer rates are discussed.
---------------------------------------------------------
Title: HERES: The Search for r-Process-Enhanced, Metal-Poor Stars
Authors: Beers, T. C.; Christlieb, N.; Bessell, M. S.; Hill, V.;
Barklem, P. S.; Korn, A.; Ryan, S. G.; Rossi, S.; Rhee, J.
2003AAS...20311217B Altcode: 2003BAAS...35Q1387B
In recent years, a handful of extremely metal-deficient stars have
been identified that exhibit moderate to large enhancements of their
abundance ratios (relative to Fe) of elements associated with the
astrophysical r-process, enabling detections of radioactive species such
as U and Th. Our understanding could be greatly improved by increasing
the numbers of known r-process-enhanced, metal-poor stars, as well
from building the sample to the point where meaningful measures of the
frequency of the phenomenon, especially as a function of metallicity,
could be ascertained. <P />We describe the present status of HERES --
The Hamburg/ESO R-process Enhanced Star survey. This survey is based
upon "snapshot" high-resolution VLT/UVES spectra of large numbers of
giants with [Fe/H] < -2.5. Spectra of sufficient quality to detect
the presence of the EuII line (4019 Å ), a distinctive neutron-capture
feature, have now been obtained for over 300 very metal-deficient
giants chosen from the Hamburg/ESO survey, along with a small number
of targets from the HK survey of Beers and colleagues. We discuss the
number of moderate- and highly- r-process enhanced stars discovered,
update our estimate of the frequency of their detection, and present a
discussion of the distribution of ∼ 20 other easily-measured elements
in each of these stars (e.g., C, Ca, Mg, Si, Co, Ni, Sr, Ba, etc.). <P
/>This work has received partial support from NSF grants AST 00-98508
and AST 00-98549. Support has also been received from the Deutsche
Forschungsgemeinschaft (Re 353/44-1), the Swedish Research Council,
PPARK (UK: PPA/O/S/1998/00658), FAPESP and CNPq (Brazil).
---------------------------------------------------------
Title: Cross sections for low-energy inelastic H+Li collisions
Authors: Belyaev, Andrey K.; Barklem, Paul S.
2003PhRvA..68f2703B Altcode:
We report calculations for the low-energy near-threshold inelastic
collision cross sections between the Li(2s,2p,3s,3p)+H(1s)
states. Results are obtained by solving the coupled-channel
equations. Order-of-magnitude estimates for higher states have been made
with the multichannel Landau-Zener model. Potentials and couplings from
H. Croft et al [J. Phys. B 32, 81 (1999)] are employed. The calculated
cross sections are much smaller than ones predicted by the classical
Thomsom atom formula currently employed in astrophysics. This result
is important for the interpretation of stellar spectra.
---------------------------------------------------------
Title: Collisional depolarization and transfer rates of spectral
lines by atomic hydrogen. II. Application to d states of neutral atoms
Authors: Derouich, M.; Sahal-Bréchot, S.; Barklem, P. S.
2003A&A...409..369D Altcode: 2003astro.ph..5018D
The theory of collisional depolarization of spectral lines by atomic
hydrogen (Derouich et al. \cite{derouich1}) is extended to d (l=2)
atomic levels. Depolarization rates, polarization and population
transfer rates are calculated and results are given as a function
of the temperature. Cross sections as a function of the effective
quantum number for a relative velocity of 10 km s<SUP>-1</SUP> are
also given together with velocity exponents lambda , if they exist,
with the assumption that the cross section varies with velocity as
v<SUP>-lambda </SUP>. A discussion of our results is presented.
---------------------------------------------------------
Title: Inelastic H+Li and H<SUP>-</SUP>+Li<SUP>+</SUP> collisions
and non-LTE Li I line formation in stellar atmospheres
Authors: Barklem, P. S.; Belyaev, A. K.; Asplund, M.
2003A&A...409L...1B Altcode: 2003astro.ph..8170B
Rate coefficients for inelastic collisions between Li and H
atoms covering all transitions between the asymptotic states
Li(2s,2p,3s,3p,3d,4s,4p,4d,4f)+H(1s) and Li<SUP>+</SUP>+H<SUP>-</SUP>
are presented for the temperature range 2000-8000 K based on recent
cross-section calculations. The data are of sufficient completeness
for non-LTE modelling of the Li I 670.8 nm and 610.4 nm features in
late-type stellar atmospheres. Non-LTE radiative transfer calculations
in both 1D and 3D model atmospheres have been carried out for test
cases of particular interest. Our detailed calculations show that
the classical modified Drawin-formula for collisional excitation and
de-excitation (Li<SUP>*</SUP>+H \rightleftharpoons Li<SUP>*'</SUP>+H)
over-estimates the cross-sections by typically several orders of
magnitude and consequently that these reactions are negligible
for the line formation process. However, the charge transfer
reactions collisional ion-pair production and mutual neutralization
(Li<SUP>*</SUP>+H \rightleftharpoons Li<SUP>+</SUP>+H<SUP>-</SUP>) are
of importance in thermalizing Li. In particular, 3D non-LTE calculations
of the Li I 670.8 nm line in metal-poor halo stars suggest that 1D
non-LTE results over-estimate the Li abundance by up to about 0.1 dex,
aggrevating the discrepancy between the observed Li abundances and
the primordial Li abundance as inferred by the WMAP analysis of the
cosmic microwave background.
---------------------------------------------------------
Title: Balmer Lines and Effective Temperatures in Cool Stars
Authors: Barklem, P. S.; Stempels, H. C.; Kochukhov, O.; Piskunov,
N.; O'Mara, B. J.
2003csss...12.1103B Altcode:
Theoretical work on the self-broadening of Balmer lines by us predicts
a large impact on model profiles, and therefore effective temperature
determinations, particularly in metal-poor stars. We present initial
results of the application to observations of a sample of cool dwarf
stars. The effective temperatures determined for our sample show
much improved agreement with the infra-red flux method results in the
literature when compared with analysis using the previously available
broadening theory.
---------------------------------------------------------
Title: Broadening of Spectral Lines by Collisions with H-atoms
Authors: O'Mara, B. J.; Barklem, P. S.
2003csss...12.1097O Altcode:
Pressure broadening of metallic lines in cool stars is dominated by
collisions with hydrogen atoms. A universal theory for broadening of
neutral metallic lines by this mechanism developed by Anstee, Barklem,
and O'Mara is briefly reviewed. Several examples of successful
application of the data are presented and future applications
discussed. Line broadening data from this theory for a large sample
of lines can be obtained by accessing the Vienna Atomic Line Database
(htmladdnormallink{www.astro.univie.ac.at/simvald}{www.astro.univie.ac.at/
vald}) or for individual lines by using software available at
htmladdnormallink{www.astro.se/simbarklem}{www.astro.uu.se/ barklem}.
---------------------------------------------------------
Title: Semi-classical theory of collisional depolarization of spectral
lines by atomic hydrogen I. Application to p states of neutral atoms
Authors: Derouich, M.; Sahal-Bréchot, S.; Barklem, P. S.; O'Mara,
B. J.
2003A&A...404..763D Altcode: 2003astro.ph..4115D
The present paper extends the method of Anstee, Barklem and
O'Mara (Anstee \cite{Anstee2}; Anstee & O'Mara \cite{Anstee1},
\cite{Anstee3}; Anstee et al. \cite{Anstee4}; Barklem \cite{Barklem3};
Barklem & O'Mara \cite{Barklem1}; Barklem et al. \cite{Barklem2}),
developed during the 1990s for collisional line broadening by atomic
hydrogen, to the depolarization of spectral lines of neutral atoms by
collisions with atomic hydrogen. In the present paper, we will limit
the calculations to p (l=1) atomic levels. The depolarization cross
sections and depolarization rates are computed. In Table \ref{cross}
cross sections as functions of the relative velocity and effective
quantum number are given, allowing for the computation for any p atomic
level. Our results are compared to quantum chemistry calculations where
possible. The sensitivity of depolarization cross sections to regions
of the potential is examined. We conclude that the accuracy obtained
with our method (<20% for the depolarization rates) is promising
for its extension to higher l-values for the interpretation of the
“second solar spectrum”. This will be the object of further papers.
---------------------------------------------------------
Title: Accurate atomic parameters for near-infrared spectral lines
Authors: Borrero, J. M.; Bellot Rubio, L. R.; Barklem, P. S.; del
Toro Iniesta, J. C.
2003A&A...404..749B Altcode:
A realistic two-component model of the quiet solar photosphere is
used to fit the intensity spectrum of the Sun in the wavelength
range 0.98-1.57 mu m. Our approach differs from earlier attempts in
many respects: proper account of convective inhomogeneities is made,
accurate collisional broadening parameters from quantum mechanical
computations are used, and the effects of possible blends in the local
continuum are corrected empirically. This allows us to derive oscillator
strengths and central wavelengths for virtually any unblended line of
the solar spectrum. The accuracy of the inferred atomic parameters,
about 0.06 dex for oscillator strengths and 5 mÅ at 1 mu m for central
wavelengths, is similar to that of the best laboratory measurements. We
apply our method to 83 near-infrared lines belonging to 6 different
atomic species. The availability of accurate oscillator strengths and
central wavelengths for lines of different species is essential for
the interpretation of high resolution spectroscopic observations. The
method is especially useful in the infrared, a wavelength domain where
laboratory measurements are scarce.
---------------------------------------------------------
Title: Heres: the Search for R-Process Enhanced, Metal-Poor Stars
Authors: Beers, Timothy C.; Christlieb, Norbert; Bessell, Mike S.;
Hill, Vanessa; Barklem, Paul S.; Ryan, Sean G.; Rossi, Silvia;
Korn, Andreas
2003IAUJD..15E..34B Altcode:
In recent years a handful of extremely metal-deficient stars have
been identified that exhibit moderate to large enhancements of their
abundance ratios (relative to Fe) of elements associated with the
astrophysical r-process enabling detections of radioactive species such
as U and Th. Our understanding could be greatly improved by increasing
the numbers of known r-process-enhanced metal-poor stars as well from
building the sample to the point where meaningful measures of the
frequency of the phenomenon especially as a function of metallicity
could be ascertained. <P />We describe the present status of HERES --
The Hamburg/ESO R-process Enhanced Star survey. This survey is based
upon ""snapshot"" high-resolution VLT/UVES spectra of large numbers
of giants with [Fe/H] < -2.5. Spectra of sufficient quality
to detect the presence of the EuII line (4019 A) a distinctive
neutron-capture feature have now been obtained for some 150-200
extremely metal-deficient giants chosen from the Hamburg/ESO survey. We
discuss the number of moderate- and highly r-process enhanced stars
discovered update our estimate of the frequency of their detection and
present a discussion of the distribution of ~ 20 other easily measured
elements in each of these stars (e.g. C Ca Mg Si Co Ni Sr Ba etc.).
---------------------------------------------------------
Title: Depolarization rates of spectral lines of neutral and singly
ionised atoms by isotropic collisions with hydrogen atoms
Authors: Derouich, M.; Sahal-Bréchot, S.; Barklem, P. S.
2003sf2a.conf...89D Altcode: 2003sf2a.confE..26D
In order to interpret quantitatively the linearly polarized spectrum
of the Sun, depolarizing collisions of the radiating and absorbing
atoms or ions with neutral hydrogen atoms of the medium have to be
included in the statistical equilibrium equations. The semi-classical
theory of collisional depolarization of spectral lines by atomic
hydrogen has been developed and applied to p (l = 1) atomic states
(M. Derouich, S. Sahal-Bréchot, P. S. Barklem, B. J. O'Mara 2003). We
present an extension of this theory to d (l=2) and f (l=3) atomic
levels. The theory is extended to p and d levels of singly ionized
atoms. Depolarization rates, polarization and population transfer
rates are calculated and results are given as a function of the
temperature. Our results are compared to quantum chemistry calculations
where possible. We conclude that our method is useful alternative of
the accurate but time consuming quantum chemistry method for obtaining
most of the depolarization rates to better than 20% accuracy.
---------------------------------------------------------
Title: Hydrogen Balmer Lines as Probes of Stellar Atmospheres
Authors: Barklem, P. S.; Piskunov, N.
2003IAUS..210P.E28B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interpretation of the Core-Wing Anomaly of Balmer Line Profiles
of Cool Ap Stars
Authors: Kochukhov, O.; Bagnulo, S.; Barklem, P. S.
2003IAUS..210P.D17K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Accurate Atomic Parameters from the Solar Spectrum
Authors: Bellot Rubio, Luis Ramon; Borrero, Juan Manuel; Barklem,
Paul; del Toro Iniesta, Jose Carlos
2003IAUJD..20E..16B Altcode:
A realistic two-component model of the quiet solar photosphere is used
to fit the full shape of the intensity profiles of unblended lines in
the solar spectrum. Our approach differs from previous attempts in many
respects: proper account of granulation inhomogeneities is made accurate
collisional broadening parameters from quantum mechanical computations
are used and possible absorptions in the local continuum due to blends
are corrected empirically. This allows us to derive oscillator strengths
and central wavelengths for any clean line with an accuracy comparable
with that of the best laboratory measurements. The availability of
very precise atomic parameters for lines of different species is
essential for the interpretation of high resolution spectroscopic
observations. Abundance determinations and investigations of granular
motions in stellar atmospheres are among the applications that would
benefit from such accurate atomic data. As an example we determine the
oscillator strengths and central wavelengths of 100 unblended lines
in the near-infrared (0.99-1.56 microns) a wavelength domain where
laboratory measurements are particularly scarce.
---------------------------------------------------------
Title: Interpretation of the Core-Wing Anomaly of Balmer Line Profiles
of Cool Ap Stars
Authors: Kochukhov, O.; Bagnulo, S.; Barklem, P. S.
2002ApJ...578L..75K Altcode:
A number of cool magnetic chemically peculiar stars exhibit abnormal
profiles of hydrogen Balmer lines. This anomaly, which is most clearly
visible in Hα, consists of a sharp transition between broad Stark
wings and an unusually narrow Doppler core. Although the core-wing
anomaly is a clear indication of an abnormal structure of the
atmospheres of cool Ap stars, it has so far eluded even qualitative
interpretation. In this Letter we report results of an attempt
to reproduce the core-wing anomaly of Balmer lines by empirical
modification of the thermal atmospheric structure. We find that it is
possible to obtain a very good fit to the inner and outer wings as well
as to reproduce the abrupt core-wing transition and widths of both Hα
and Hβ by increasing the temperature by 500-1000 K at intermediate
atmospheric layers (-4<=logτ<SUB>5000</SUB><=-1). Thus,
detailed analysis of hydrogen lines provides a very useful method
for revealing the atmospheric structure of cool Ap stars and should
serve as a crucial test for future self-consistent model atmospheres
of peculiar stars. Based on observations obtained at the European
Southern Observatory, Very Large Telescope.
---------------------------------------------------------
Title: A stellar relic from the early Milky Way
Authors: Christlieb, N.; Bessell, M. S.; Beers, T. C.; Gustafsson, B.;
Korn, A.; Barklem, P. S.; Karlsson, T.; Mizuno-Wiedner, M.; Rossi, S.
2002Natur.419..904C Altcode: 2002astro.ph.11274C
The chemical composition of the most metal-deficient stars largely
reflects the composition of the gas from which they formed. These
old stars provide crucial clues to the star formation history and the
synthesis of chemical elements in the early Universe. They are the local
relics of epochs otherwise observable only at very high redshifts; if
totally metal-free (`population III') stars could be found, this would
allow the direct study of the pristine gas from the Big Bang. Earlier
searches for such stars found none with an iron abundance less than
1/10,000 that of the Sun, leading to the suggestion that low-mass
stars could form from clouds above a critical iron abundance. Here we
report the discovery of a low-mass star with an iron abundance as low
as 1/200,000 of the solar value. This discovery suggests that population
III stars could still exist-that is, that the first generation of stars
also contained long-lived low-mass objects. The previous failure to
find them may be an observational selection effect.
---------------------------------------------------------
Title: Abundance analysis of two late A-type stars HD 32115 and
HD 37594
Authors: Bikmaev, I. F.; Ryabchikova, T. A.; Bruntt, H.; Musaev, F. A.;
Mashonkina, L. I.; Belyakova, E. V.; Shimansky, V. V.; Barklem, P. S.;
Galazutdinov, G.
2002A&A...389..537B Altcode: 2002astro.ph..6143B
We have performed abundance analysis of two slowly rotating, late
A-type stars, HD 32115 (HR 1613) and HD 37594 (HR 1940), based on
obtained echelle spectra covering the spectral range 4000-9850 Å. These
spectra allowed us to identify an extensive line list for 31 chemical
elements, the most complete to date for A-type stars. Two approaches
to abundance analysis were used, namely a “manual” (interactive)
and a semi-automatic procedure for comparison of synthetic and
observed spectra and equivalent widths. For some elements non-LTE
(NLTE) calculations were carried out and the corresponding corrections
have been applied. The abundance pattern of HD 32115 was found to be
very close to the solar abundance pattern, and thus may be used as an
abundance standard for chemical composition studies in middle and late
A stars. Further, its Hα line profile shows no core-to-wing anomaly
like that found for cool Ap stars and therefore also may be used as
a standard in comparative studies of the atmospheric structures of
cool, slowly rotating Ap stars. HD 37594 shows a metal deficiency
at the level of -0.3 dex for most elements and triangle-like cores
of spectral lines. This star most probably belongs to the delta Sct
group. Based on observations obtained at the 2-m telescope of Peak
Terskol Observatory near Elbrus mountain, International Center of
Astronomical and Medical-Ecological Researches, Russia. Table 4 is
only available in electronic form at http://www.edpsciences.org
---------------------------------------------------------
Title: Detailed analysis of Balmer lines in cool dwarf stars
Authors: Barklem, P. S.; Stempels, H. C.; Allende Prieto, C.;
Kochukhov, O. P.; Piskunov, N.; O'Mara, B. J.
2002A&A...385..951B Altcode: 2002astro.ph..1537B
An analysis of Hα and Hβ spectra in a sample of 30 cool dwarf and
subgiant stars is presented using MARCS model atmospheres based on the
most recent calculations of the line opacities. A detailed quantitative
comparison of the solar flux spectra with model spectra shows that
Balmer line profile shapes, and therefore the temperature structure
in the line formation region, are best represented under the mixing
length theory by any combination of a low mixing-length parameter alpha
and a low convective structure parameter y. A slightly lower effective
temperature is obtained for the sun than the accepted value, which we
attribute to errors in models and line opacities. The programme stars
span temperatures from 4800 to 7100 K and include a small number of
population II stars. Effective temperatures have been derived using
a quantitative fitting method with a detailed error analysis. Our
temperatures find good agreement with those from the Infrared Flux
Method (IRFM) near solar metallicity but show differences at low
metallicity where the two available IRFM determinations themselves are
in disagreement. Comparison with recent temperature determinations
using Balmer lines by Fuhrmann (\cite{fuhrmann98, fuhrmann00}),
who employed a different description of the wing absorption due
to self-broadening, does not show the large differences predicted
by Barklem et al. (\cite{bpo:hyd}). In fact, perhaps fortuitously,
reasonable agreement is found near solar metallicity, while we find
significantly cooler temperatures for low metallicity stars of around
solar temperature. Based on observations collected at the Isaac Newton
Telescope, La Palma, Spain, and McDonald Observatory, Texas, USA.
---------------------------------------------------------
Title: Comments on alternative calculations of the broadening of
spectral lines of neutral sodium by H-atom collisions
Authors: Barklem, P. S.; O'Mara, B. J.
2001JPhB...34.4785B Altcode: 2001astro.ph.10106B
With the exception of the sodium D-lines, recent calculations of line
broadening cross sections for several multiplets of sodium by Leininger
et al (Leininger T, Gadéa F X and Dickinson A 2000 J. Phys. B:
At. Mol. Opt. Phys. 33 1805) are in substantial disagreement with cross
sections interpolated from the tables of Anstee and O'Mara (Anstee and
O'Mara 1995 Mon. Not. R. Astron. Soc. 276 859) and Barklem and O'Mara
(Barklem P S and O'Mara B J 1997 Mon. Not. R. Astron. Soc. 290 102). The
discrepancy is as large as a factor of 3 for the 3p-4d multiplet. The
two theories are tested by using the results of each to synthesize
lines in the solar spectrum. It is found that generally the data from
the theory of Anstee, Barklem and O'Mara produce the best match to
the observed solar spectrum. It is found, using a simple model for
reflection of the optical electron by the potential barrier between
the two atoms, that the reflection coefficient is too large for avoided
crossings with the upper states of subordinate lines to contribute to
line broadening, supporting the neglect of avoided ionic crossings by
Anstee, Barklem and O'Mara for these lines. The large discrepancies
between the two sets of calculations is a result of an approximate
treatment of avoided ionic crossings for these lines by Leininger
et al (Leininger T, Gadéa F X and Dickinson A 2000 J. Phys. B:
At. Mol. Opt. Phys. 33 1805).
---------------------------------------------------------
Title: Chemical Abundances from Inversions of Stellar Spectra:
Analysis of Solar-Type Stars with Homogeneous and Static Model
Atmospheres
Authors: Allende Prieto, Carlos; Barklem, Paul S.; Asplund, Martin;
Ruiz Cobo, Basilio
2001ApJ...558..830A Altcode: 2001astro.ph..5262P; 2001astro.ph..5262A
Spectra of late-type stars are usually analyzed with static model
atmospheres in local thermodynamic equilibrium (LTE) and a homogeneous
plane-parallel or spherically symmetric geometry. The energy balance
requires particular attention, as two elements that are particularly
difficult to model play an important role: line blanketing and
convection. Inversion techniques are able to bypass the difficulties
of a detailed description of the energy balance. Assuming that the
atmosphere is in hydrostatic equilibrium and LTE, it is possible
to constrain its structure from spectroscopic observations. Among
the most serious approximations still implicit in the method is a
static and homogeneous geometry. In this paper, we take advantage of a
realistic three-dimensional radiative hydrodynamical simulation of the
solar surface to check the systematic errors incurred by an inversion
assuming a plane-parallel horizontally-homogeneous atmosphere. The
thermal structure recovered resembles the spatial and time average
of the three-dimensional atmosphere. Furthermore, the abundances
retrieved are typically within 10% (0.04 dex) of the abundances used
to construct the simulation. The application to a fairly complete data
set from the solar spectrum provides further confidence in previous
analyses of the solar composition. There is only a narrow range of
one-dimensional thermal structures able to fit the absorption lines in
the spectrum of the Sun. With our carefully selected data set, random
errors are about a factor of 2 smaller than systematic errors. A small
number of strong metal lines can provide very reliable results. We
foresee no major difficulties in applying the technique to other
similar stars, and obtaining similar accuracies, using spectra with
λ/δλ~5×10<SUP>4</SUP> and a signal-to-noise ratio as low as 30.
---------------------------------------------------------
Title: Broadening of Spectral Lines of Singly Ionised Atoms
by Collisions with Neutral Hydrogen Atoms (CD-ROM Directory:
contribs/barklem2)
Authors: Barklem, P. S.; O'Mara, B. J.
2001ASPC..223..772B Altcode: 2001csss...11..772B
No abstract at ADS
---------------------------------------------------------
Title: Recent Developments of the VALD Database (CD-ROM Directory:
contribs/stempels)
Authors: Stempels, H. C.; Piskunov, N.; Barklem, P. S.
2001ASPC..223..878S Altcode: 2001csss...11..878S
No abstract at ADS
---------------------------------------------------------
Title: Hydrogen Line Formation in Cool Stars (CD-ROM Directory:
contribs/barklem1)
Authors: Barklem, P. S.; Kochukhov, O.; Piskunov, N.; O'Mara, B. J.;
Stempels, H. C.
2001ASPC..223..766B Altcode: 2001csss...11..766B
No abstract at ADS
---------------------------------------------------------
Title: Self-broadening in Balmer line wing formation in stellar
atmospheres
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000A&A...363.1091B Altcode: 2000astro.ph.10022B
Details of a theory of self-broadening of hydrogen lines are
presented. The main features of the new theory are that the
dispersive-inductive components of the interaction (van der Waals
forces) have been included, and the resonance components have been
computed by perturbation theory without the use of the multipole
expansion. The theory is applied to lower Balmer lines and the
theoretical and observational impact of the new broadening theory
is examined. It is shown that this theory leads to considerable
differences in the predicted line profiles in cool stars when compared
with previous theories which include only resonance interactions. In
particular, the effect is found to be very important in metal poor
stars. The theory provides a natural explanation for the behaviour
of effective temperatures derived from Balmer lines by others using
a theory which includes only resonance broadening. When applied to
Balmer lines in the solar spectrum the theory predicts an improved
agreement between observed and computed profiles for models which
also match limb darkening curves and rules out a model which does
not. However significant discrepancies still remain which could be
due to inadequacies in our theory or the atmospheric model or both.
---------------------------------------------------------
Title: A list of data for the broadening of metallic lines by neutral
hydrogen collisions
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000A&AS..142..467B Altcode:
A list of data for the broadening by neutral hydrogen collisions of many
astrophysically important spectral lines, which has been incorporated
into the Vienna Atomic Line Database (VALD), is presented. Data for
lines of neutral atoms are interpolated from the tabulated data of
Anstee & O'Mara (\cite{ao:sp}), Barklem & O'Mara (\cite{bo:pd}),
and Barklem et al. (\cite{bor:df}). Data for lines of singly ionised
atoms are compiled from the calculations by Barklem & O'Mara
(\cite{bo:ion1,bo:ion2}). The list at present contains data for
4891 lines between 2300 and 13000 Ä of elements from Li to Ni. We
examine the statistical impact of the new theory by comparison with
the previously available data. We also demonstrate the direct effect on
spectral synthesis calculations. Table~1 is only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via anonymous ftp to ftp.astro.uu.se/pub/Spectra/barklem/hlist/
---------------------------------------------------------
Title: VizieR Online Data Catalog: Broadening of metallic lines by
H collisions (Barklem+ 2000)
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000yCat..41420467B Altcode:
File table1 is a list of theoretical data for the broadening of metallic
lines by collisions with neutral hydrogen atoms. The list contains data
for 4891 spectral lines between 2300 and 13000 Angstroms of elements
from Li to Ni. (1 data file).
---------------------------------------------------------
Title: Self broadening of hydrogen lines: initial results
Authors: Barklem, P. S.; Piskunov, N.; O'Mara, B. J.
2000A&A...355L...5B Altcode:
For the first time broadening by both resonance and dispersive-inductive
interactions with H-atoms are included in the formation of Balmer lines
in cool stars, without the use of a multipole expansion. Comparison of
synthetic profiles with observed profiles for the Sun and two late F
dwarfs shows that this improvement in broadening theory accounts for
some of the problems found in previous work. It is anticipated that
planned future developments in the theory of self broadening will lead
to further improve ments in the modelling of cool star atmospheres.
---------------------------------------------------------
Title: Broadening of lines of Beii, Srii and Baii by collisions with
hydrogen atoms and the solar abundance of strontium
Authors: Barklem, P. S.; O'Mara, B. J.
2000MNRAS.311..535B Altcode:
In a previous paper by the present authors the theory of Anstee
and O'Mara for the broadening of spectral lines of neutral atoms by
collisions with hydrogen atoms was extended to singly ionized atoms. In
this paper we apply the method to the resonance and triplet lines of
ionized strontium, the infrared triplet of ionized barium, and the
resonance lines of ionized beryllium. Analysis of five lines of ionized
strontium, previously regarded as too strong for an abundance analysis,
and two lines of neutral strontium results in a solar abundance of
strontium of log(N<SUB>Sr</SUB>N<SUB>H</SUB>)+12=2.92+/-0.05, which
is entirely consistent with the meteoritic value.
---------------------------------------------------------
Title: Line Broadening Cross Sections for the Broadening of
Transitions of Neutral Atoms by Collisions with Neutral Hydrogen
Authors: Barklem, P. S.; Anstee, S. D.; O'Mara, B. J.
1998PASA...15..336B Altcode:
Line broadening cross sections for the broadening of spectral lines by
collisions with neutral hydrogen atoms have been tabulated by Anstee
& O'Mara (1995), Barklem & O'Mara (1997) and Barklem, O'Mara
& Ross (1998) for s-p, p-s, p-d, d-p, d-f and f-d transitions. To
make these data more accessible to the end user, fortran code which
interpolates in these tabulations has been prepared and placed on
the World Wide Web. It should be easy to incorporate this code into
existing spectrum synthesis programs or to use it in a stand-alone mode
to compute line broadening cross sections for specific transitions. The
use of the code is demonstrated by its application to two transitions
of astrophysical interest.
---------------------------------------------------------
Title: The broadening of strong lines of Ca^+, Mg^+ and Ba^+ by
collisions with neutral hydrogen atoms
Authors: Barklem, P. S.; O'Mara, B. J.
1998MNRAS.300..863B Altcode:
The theory of Anstee & O'Mara is extended to the line broadening of
transitions of singly ionized atoms by collisions with neutral hydrogen
atoms. The theory is used to calculate broadening cross-sections
for strong lines of singly ionized calcium, magnesium and barium. The
broadening cross-sections calculated are compared with both theoretical
and empirical results of other workers.
---------------------------------------------------------
Title: The Broadening of Spectral Lines by Collisions with Neutral
Hydrogen Atoms
Authors: Barklem, P. S.
1998PhDT........18B Altcode:
In this thesis the theory of collisional broadening by neutral hydrogen
of Anstee and O'Mara (1991,1992,1995) for s-p and p-s transitions
of neutrals is extended and applied to both p-d, d-p, d-f and f-d
transitions of neutral atoms, and the broadening of transitions of
ions. The interaction between a ground state hydrogen atom with a
generic neutral atom, is considered using Rayleigh-Schrödinger
perturbation theory. The usual second order expression for the
interaction energy between the two atoms involves an infinite sum
over virtual states of the two-atom system, and an energy denominator
which is the energy debt incurred when the two atom system makes a
transition from the state of interest to a virtual state. Unsöld
(1927,1955) showed that the expression for the in teraction energy
can be greatly simplified if the variable energy debt incurred in
making a transition from the state of interest to a virtual state is
replaced by a fixed debt E<SUB>p</SUB>. Closure can then be used to
complete the sum over the virtual states leading to an expression
for the interaction energy in terms of diagonal matrix elements of
V<SUP>2</SUP> (where V is the electrostatic interaction between the
two atoms), and E<SUB>p</SUB>. This is commonly referred to as the
Unsöld approximation. It is the most important approximation in the
development of the treatment of spectral line broadening presented
in this thesis. Expressions for the interaction energy between a
ground state hydrogen atom and a generic neutral atom in both d- and
f-states are presented. Adiabatic potential curves calculated from code
written to compute these expressions are presented. For interactions
of neutral atoms, the Unsöld value of E<SUB>p</SUB>=-4/9 atomic
units is used throughout. Code was written to compute line broadening
cross-sections for p-d, d-p, d-f and f-d transitions of neutral atoms,
using the semi-classical procedure of Roueff (1974) adapted for these
transitions. Firstly, the dependence of cross-sections on regions
of the potential curves is examined. It is concluded that as found
by Anstee and O'Mara (1991,1992) for s-p and p-s transitions, line
broadening is insensitive to close collisions and most sensitive
to intermediate range interactions. Evidence for this conclusion
is presented. The influence of the use of the approximate value of
E<SUB>p</SUB>=-4/9 for the energy denominator on the broadening of
neutral atom transitions is fully investigated. The dependence on the
choice of E<SUB>p</SUB> is shown to be small over the domain of expected
values. Line broadening cross-section results are presented for selected
specific transitions. Results are also presented in tabular form for
cross-sections for general p-d, d-p, d-f and f-d transitions. The
cross-sections are tabulated with effective principal quantum number
for each state, for a relative perturber velocity of 10<SUP>4</SUP>
m/s. The cross-sections are fitted to a power law relationship with
velocity, of the form σ(v) ∝ v<SUP>α</SUP>. The velocity parameter
α is similarly tabulated. The extent of the tables is such that most
transitions corresponding to these angular momentum states, that will be
astrophysically important, should fall within the tables. The results
are tested by application to solar spectra. The data is applied to
strong lines and abundances for these elements derived and compared
with meteoritic abundances. The derived elemental abundances are
found to be consistent with meteoritic and currently accepted values,
to within the uncertainties in the f-values. Finally, the theory
is extended to the broadening of spectral lines of singly ionised
atoms. Required modifications to the current interaction potentials are
presented. The use of the Unsöld approximation requires a slightly
modified approach for ions. A method is presented for calculation of
E<SUB>p</SUB> that is suitable for the upper and lower states of strong
transitions. Dispersion coefficients C<SUB>6</SUB> and subsequent
energy denominators E_p are presented for selected states of ionised
atoms. Using these results, broadening cross-sections are presented for
the resonance transitions of Ca^+, Mg^+ and Ba^+, and the infrared 4p-3d
triplet of Ca<SUP>+</SUP>. The triplet lines are tested in the solar
spectra, by comparison with empirically determined cross-sections. The
calculations for other transition s are compared with both theoretical
calculations and empirical determinations by other workers.
---------------------------------------------------------
Title: The broadening of d-f and f-d transitions by collisions with
neutral hydrogen atoms
Authors: Barklem, P. S.; O'Mara, B. J.; Ross, J. E.
1998MNRAS.296.1057B Altcode:
The theory of Anstee & O'Mara for the broadening of spectral
lines owing to collisions by neutral hydrogen atoms is extended to
d-f and f-d transitions of neutral atoms. Width cross-sections are
tabulated against effective principal quantum numbers for the upper and
lower states of the transition, for a relative collision velocity of
10^4ms^-1. The cross-sections are fitted to a variation with velocity
of v^-alpha, and results for the velocity parameter alpha are similarly
tabulated. The data are tested by application to d-f spectral lines in
the solar spectrum. The derived abundances are consistent with those
for meteorites.
---------------------------------------------------------
Title: The broadening of spectral lines by collisions with neutral
hydrogen atoms
Authors: Barklem, Paul Stuart
1998PhDT.......417B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The broadening of p-d and d-p transitions by collisions with
neutral hydrogen atoms
Authors: Barklem, P. S.; O'Mara, B. J.
1997MNRAS.290..102B Altcode:
The collisional broadening theory of Anstee & O'Mara for s-p and
p-s transitions by collisions with atomic hydrogen is extended to p-d
and d-p transitions. Width cross-sections for collisional broadening
of atomic lines corresponding to p-d and d-p transitions by neutral
hydrogen atoms are tabulated as a function of effective principal
quantum numbers for the upper and lower states, for a relative velocity
of 10^4ms^-1. The cross-sections vary with velocity as v^-alpha,
and results for the parameter alpha are similarly tabulated. The
cross-sections are tested by application to synthesis of suitable
strong solar lines. The derived abundances are consistent with
meteoritic values.
---------------------------------------------------------
Title: The broadening of spectral lines which correspond to $p$--$d$
and $d$--$p$ transitions by collisions with neutral hydrogen atoms
Authors: Barklem, P. S.; O'Mara, B. J.
1997IAUS..189P..82B Altcode: 1998IAUS..189P..82B
No abstract at ADS
