An investigation of the double-mode Cepheid TU Cassiopeiae - I. Atmospheric parameters and chemical composition

AbstractAtmospheric parameters and abundances of 25 elements were determined from two spectrograms of TU Cas (with dispersion 9 Å/mm) obtained in 1977 and 1990. We find Teff= 5860 - 6000K; logg = 1.0 - 1.5; and vt = 2.9 - 5.3 km/s.The value of [Fe/H] ∼ -0.5 testifies to the fact that TU Cas is deficient in metals compared with other double-mode Cepheids. More exact values of [Fe/H] for 9 double-mode Cepheids in the Southern Hemisphere (Barrell 1982), V367 Set (a member of the open cluster NGC 6649) and our value for TU Cas all show a good correlation with P1/P0. As the atmospheric Fe abundance increases, the ratio P1/P0 decreases.Our measured values for abundances (in brackets) of various elements in the atmosphere of TU Cas are: C (8.26), Na (6.32), Mg (7.07), Si (6.85), S (6.96), Ca (5.88), Sc (2.71), Ti (4.34), V (3.35), Cr (5.29), Mn (4.92), Fe (6.94), Co (4.47), Ni (5.70), Zn (3.63), Sr (2.00), Y (2.17), Zr (2.21), Ba (1.41), La (1.08), Ce (0.96), Nd (0.82), Sm (0.42), Eu (1.04), and Gd (0.92).

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Heavy metal enrichment in the intermediate He-sdOB pulsator Feige 46

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936247 ◽

2019 ◽

Vol 629 ◽

pp. A148 ◽

Cited By ~ 5

Author(s):

M. Latour ◽

M. Dorsch ◽

U. Heber

Keyword(s):

Heavy Metal ◽

Chemical Composition ◽

Optical Spectrum ◽

Atmospheric Parameters ◽

Metal Enrichment ◽

Uv Spectrum ◽

Abundance Pattern ◽

Upper Limits ◽

Kinematic Properties ◽

Heavy Metal Enrichment

The intermediate He-enriched hot subdwarf star Feige 46 was recently reported as the second member of the V366 Aqr (or He-sdOBV) pulsating class. Feige 46 is very similar to the prototype of the class, LS IV − 14°116, not only in terms of pulsational properties, but also in terms of atmospheric parameters and kinematic properties. LS IV − 14°116 is additionally characterized by a very peculiar chemical composition, with extreme overabundances of the trans-iron elements Ge, Sr, Y, and Zr. We investigate the possibility that the similarity between the two pulsators extends to their chemical composition. We retrieved archived optical and UV spectroscopic observations of Feige 46 and performed an abundance analysis using model atmospheres and synthetic spectra computed with TLUSTY and SYNSPEC. In total, we derived abundances for 16 elements and provide upper limits for four additional elements. Using absorption lines in the optical spectrum of the star we measure an enrichment of more than 10 000× solar for yttrium and zirconium. The UV spectrum revealed that strontium is equally enriched. Our results confirm that Feige 46 is not only a member of the now growing group of heavy metal subdwarfs, but also has an abundance pattern that is remarkably similar to that of LS IV − 14°116.

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14. White Dwarf Atmospheres

Symposium - International Astronomical Union ◽

10.1017/s0074180900097138 ◽

1971 ◽

Vol 42 ◽

pp. 81-96 ◽

Cited By ~ 2

Author(s):

V. Weidemann

Keyword(s):

Chemical Composition ◽

Observational Data ◽

Effective Temperature ◽

White Dwarf ◽

General Information ◽

Stellar Atmospheres ◽

Surface Gravity ◽

Atmospheric Parameters

We first consider the general information scheme for the interpretation of observational data (Figure 1). From the relations plotted it is evident that (in going from left to right) this scheme can only be solved if distances are known and if we are able to determine the atmospheric parameters: effective temperature, Teff, surface gravity, g, and chemical composition from observations of colors and spectra – which is the genuine task of the theory of stellar atmospheres.

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Confronting the Gaia and NLTE spectroscopic parallaxes for the FGK stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317005683 ◽

2017 ◽

Vol 12 (S330) ◽

pp. 327-328 ◽

Cited By ~ 1

Author(s):

Tatyana Sitnova ◽

Lyudmila Mashonkina ◽

Yury Pakhomov

Keyword(s):

Chemical Composition ◽

Chemical Evolution ◽

Spectroscopic Method ◽

Atmospheric Parameters ◽

Late Type ◽

Chemical Abundances ◽

Stellar Chemical Composition ◽

Cool Stars ◽

The Galaxy

AbstractThe understanding of the chemical evolution of the Galaxy relies on the stellar chemical composition. Accurate atmospheric parameters is a prerequisite of determination of accurate chemical abundances. For late type stars with known distance, surface gravity (log g) can be calculated from well-known relation between stellar mass, Teff, and absolute bolometric magnitude. This method weakly depends on model atmospheres, and provides reliable log g. However, accurate distances are available for limited number of stars. Another way to determine log g for cool stars is based on ionisation equilibrium, i.e. consistent abundances from lines of neutral and ionised species. In this study we determine atmospheric parameters moving step-by-step from well-studied nearby dwarfs to ultra-metal poor (UMP) giants. In each sample, we select stars with the most reliable Teff based on photometry and the distance-based log g, and compare with spectroscopic gravity calculated taking into account deviations from local thermodinamic equilibrium (LTE). After that, we apply spectroscopic method of log g determination to other stars of the sample with unknown distances.

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Systematic differences in the spectroscopic analysis of red giants

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833739 ◽

2019 ◽

Vol 622 ◽

pp. A111 ◽

Cited By ~ 5

Author(s):

D. Slumstrup ◽

F. Grundahl ◽

V. Silva Aguirre ◽

K. Brogaard

Keyword(s):

Chemical Composition ◽

Equivalent Width ◽

Spectroscopic Analysis ◽

Spectroscopic Method ◽

Quality Data ◽

High Signal ◽

Red Giants ◽

Atmospheric Parameters ◽

Optical Telescope ◽

Atomic Parameters

Aims. A spectroscopic analysis of stellar spectra can be carried out using multiple approaches such as different methods, line lists, atmospheric models, atomic parameters, and solar abundances. The resulting atmospheric parameters from these choices can vary beyond the quoted uncertainties in the literature. We characterize these differences by systematically comparing some of the commonly adopted ingredients such as line lists, equivalent width measurements, and atomic parameters. Methods. High-resolution and high signal-to-noise (S/N) spectroscopic data of one helium-core-burning red giant star in each of the three open clusters, NGC 6819, M67, and NGC 188 were obtained with the FIES spectrograph at the Nordic Optical Telescope. The M67 target was used to benchmark the analysis, as it is a well-studied cluster with asteroseismic data from the K2 mission. For the other two clusters we obtained higher quality data than had been analyzed before, which allows us to establish their chemical composition more securely. Using a line by line analysis, we tested several different combinations of line lists and programs to measure equivalent widths of stellar absorption lines to characterize systematic differences within the same spectroscopic method. Results. The obtained parameters for the benchmark star in M67 vary up to ~170 K in effective temperature, ~0.4 dex in log g and ~0.25 dex in [Fe/H] between the tested setups. Using the combination of an equivalent width measurement program and line list that best reproduce the inferred surface gravity from asteroseismology, we determined the atmospheric parameters for the three stars and securely established the chemical composition of NGC 6819 to be close to solar, [Fe/H] = −0.02 ± 0.01 dex. Conclusions. We highlighted the significantly different results obtained with different combinations of line lists, programs, and atomic parameters. The results emphasize the importance of benchmark stars studied with several methods to anchor spectroscopic analyses.

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Atmospheric parameters and chemical composition of the ultra-cool roAp star HD 213637

Astronomy and Astrophysics ◽

10.1051/0004-6361:20030506 ◽

2003 ◽

Vol 404 (2) ◽

pp. 669-676 ◽

Cited By ~ 24

Author(s):

O. Kochukhov

Keyword(s):

Chemical Composition ◽

Atmospheric Parameters ◽

Roap Star

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Using open clusters as tracers of the galactic disk history

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317008225 ◽

2017 ◽

Vol 13 (S334) ◽

pp. 312-313

Author(s):

Orlando J. Katime Santrich ◽

Silvia Rossi ◽

Yuri Abuchaim ◽

Geraldo Gonçalves

Keyword(s):

Chemical Composition ◽

High Resolution ◽

Spectroscopic Analysis ◽

Galactic Disk ◽

Dynamical Behavior ◽

Open Clusters ◽

Atmospheric Parameters ◽

Giant Stars ◽

Stellar Formation ◽

Formation And Evolution

AbstractOpen clusters are important objects to study the galactic structure and its dynamical behavior as well as the stellar formation and evolution. We carried out a spectroscopic analysis to derive atmospheric parameters and chemical composition for 52 giant stars within 9 galactic open clusters. We have used the high-resolution spectra from FEROS, HARPS and UVES in the ESO archive. The methodology used is based on LTE-hypothesis. Abundances of C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Ni, YII, LaII, CeII, and NdII were calculated. Although most of these clusters present spectroscopic analysis in the literature, some CNO and s-process abundances were not previously estimated or were calculated with high uncertainties. Several lines of such elements were identified and used to calculate new abundances and improve some previous one.

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Abundances of seven red giants in the open cluster NGC 3114

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309991803 ◽

2009 ◽

Vol 5 (S266) ◽

pp. 495-498

Author(s):

C. B. Pereira ◽

C. Quireza

Keyword(s):

Chemical Composition ◽

Chemical Analysis ◽

Galactic Disk ◽

Open Cluster ◽

Open Clusters ◽

Red Giants ◽

The Sun ◽

Atmospheric Parameters ◽

Red Giant ◽

Good Agreement

AbstractWe present a chemical analysis of seven red giants in the open cluster NGC 3114. Our main goal is to investigate the chemical composition of this cluster, which is not yet available in the literature. We employed the FEROS spectrograph on the ESO 2.2m telescope. Atmospheric parameters and metallicity were derived from the measured equivalent widths of several iron lines using the spectral code moog and Kurucz model atmospheres. We obtained the abundances of O, Al, Ca, Mg, Si, Ti, Ni, Cr, Sc, Y, Zr, La, Ce and Nd by measuring the equivalent widths of the absorption lines of these elements. A mean metallicity of [Fe/H] = 0.05 ± 0.13 relative to the Sun was determined from the data of the red-giant members. This result is in good agreement with the Galactic-disk radial distribution of iron traced by open clusters. We did not find any intrinsic star-to-star scatter in the [element/Fe] ratios for the stars in this cluster. We compare our results with investigations of other open clusters. An age of 8.2 Gyr is derived from isochrone fits.

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Evidence of vertical abundance stratification in the SB1 star HD 161660: a new HgMn

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3108 ◽

2020 ◽

Vol 499 (3) ◽

pp. 3720-3727

Author(s):

G Catanzaro ◽

M Giarrusso ◽

M Munari ◽

F Leone

Keyword(s):

Chemical Composition ◽

Rotational Velocity ◽

Homogeneous Distribution ◽

Atmospheric Parameters ◽

Isotopic Mixture ◽

Fundamental Parameters ◽

Solar Composition ◽

Chemical Pattern ◽

Balmer Lines ◽

Archive Data

ABSTRACT In this paper, we present a detailed spectroscopic study of the SB1 system HD 161660. New spectroscopic observations have been obtained by us with Catania Astrophysical Observatory Spectropolarimeter (CAOS@OAC). Combining these observations with archive data from [email protected], we derived atmospheric parameters as temperature and gravity (from the fit of Balmer lines), microturbulence and rotational velocity (from metal lines), and chemical composition. We found underabundances of helium, carbon, magnesium, sulphur and chromium, overabundances of neon, phosphorus, argon, manganese, xenon, and mercury. All other elements have solar composition. In particular, mercury abundance is derived taking into account an isotopic mixture different from the terrestrial one (essentially pure 202Hg). Considering this chemical pattern, we definitively confirm HD 161660 is an HgMn star. Further, variability of equivalent widths points out a non-homogeneous distribution of helium and magnesium over stellar surface. As to iron and phosphorus, we found a non-constant abundance with the optical depth, a result currently considered an evidence of vertical stratification. Finally, we improved the fundamental parameters characterizing the HD 161660 orbit.

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