Metal abundances in the atmosphere of the bright component of ? Sgr

V. V. Leushin; G. P. Topil'skaya

doi:10.1007/bf01004072

Recent Advances in High Dispersion Spectroscopy of Globular Cluster Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900035610 ◽

1988 ◽

Vol 132 ◽

pp. 525-530

Author(s):

Raffaele G. Gratton

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

High Dispersion ◽

Photographic Material ◽

Recent Advances ◽

Metal Abundances ◽

Ccd Detectors ◽

Major Progress

The use CCD detectors has allowed a major progress in abundance derivations for globular cluster stars in the last years. Abundances deduced from high dispersion spectra now correlates well with other abundance indicators. I discuss some problems concerning the derivation of accurate metal abundances for globular clusters using high dispersion spectra from both the old photographic and the most recent CCD data. The discrepant low abundances found by Cohen (1980), from photographic material for M71 giants, are found to be due to the use of too high microturbulences.

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Abundances in the Gaseous Galactic Halo

Highlights of Astronomy ◽

10.1017/s1539299600020049 ◽

1998 ◽

Vol 11 (1) ◽

pp. 86-89

Author(s):

Ulysses J. Sofia

Keyword(s):

Interstellar Medium ◽

Gas Phase ◽

High Velocity ◽

Galactic Halo ◽

Solar Neighborhood ◽

Local Interstellar Medium ◽

The Galaxy ◽

Metal Abundances ◽

High Velocity Clouds

Abstract The well measured gas-phase abundances in the low halo suggest that this region of the Galaxy has total (gas plus dust) metal abundances which are close to those in the solar neighborhood. The gas-phase abundances in the halo are generally higher than those seen in the disk, however, this affect is likely due to the destruction of dust in the halo clouds. Observations of high velocity clouds (HVCs) in the halo suggest that these clouds have metal abundances which are substantially lower than those measured for the local interstellar medium. These determinations, however, are often of lower quality than those for the low halo because of uncertainties in the hydrogen abundances along the sightlines, in the incorporation of elements into dust, and in the partial ionization of the clouds.

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Helium, [Fe/H] Abundances and the HR (Log TEFF, MBol) Diagram With Hipparcos Data of The Four Nearest Open Clusters: Hyades, Coma Berenices, The Pleiades and Praesepe

Highlights of Astronomy ◽

10.1017/s1539299600022206 ◽

1998 ◽

Vol 11 (1) ◽

pp. 565-565

Author(s):

G. Cayrel de Strobel ◽

R. Cayrel ◽

Y. Lebreton

Keyword(s):

Main Sequence ◽

Open Clusters ◽

Main Sequence Stars ◽

Spectroscopic Analyses ◽

Solar Metallicity ◽

Metal Abundances ◽

The Mean ◽

The Moment ◽

The One ◽

Best Fit

After having studied in great detail the observational HR diagram (log Teff, Mbol) composed by 40 main sequence stars of the Hyades (Perryman et al.,1997, A&A., in press), we have tried to apply the same method to the observational main sequences of the three next nearest open clusters: Coma Berenices, the Pleiades, and Praesepe. This method consists in comparing the observational main sequence of the clusters with a grid of theoretical ZAMSs. The stars composing the observational main sequences had to have reliable absolute bolometric magnitudes, coming all from individual Hipparcos parallaxes, precise bolometric corrections, effective temperatures and metal abundances from high resolution detailed spectroscopic analyses. If we assume, following the work by Fernandez et al. (1996, A&A,311,127), that the mixing-lenth parameter is solar, the position of a theoretical ZAMS, in the (log Teff, Mbol) plane, computed with given input physics, only depends on two free parameters: the He content Y by mass, and the metallicity Z by mass. If effective temperature and metallicity of the constituting stars of the 4 clusters are previously known by means of detailed analyses, one can deduce their helium abundances by means of an appropriate grid of theoretical ZAMS’s. The comparison between the empirical (log Teff, Mbol) main sequence of the Hyades and the computed ZAMS corresponding to the observed metallicity Z of the Hyades (Z= 0.0240 ± 0.0085) gives a He abundance for the Hyades, Y= 0.26 ± 0.02. Our interpretation, concerning the observational position of the main sequence of the three nearest clusters after the Hyades, is still under way and appears to be greatly more difficult than for the Hyades. For the moment we can say that: ‒ The 15 dwarfs analysed in detailed in Coma have a solar metallicity: [Fe/H] = -0.05 ± 0.06. However, their observational main sequence fit better with the Hyades ZAMS. ‒ The mean metallicity of 13 Pleiades dwarfs analysed in detail is solar. A metal deficient and He normal ZAMS would fit better. But, a warning for absorption in the Pleiades has to be recalled. ‒ The upper main sequence of Praesepe, (the more distant cluster: 180 pc) composed by 11 stars, analysed in detail, is the one which has the best fit with the Hyades ZAMS. The deduced ‘turnoff age’ of the cluster is slightly higher than that of the Hyades: 0.8 Gyr instead of 0.63 Gyr.

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Statistical properties of metal abundances of the intracluster medium in the central region of clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.2000.03204.x ◽

2000 ◽

Vol 313 (1) ◽

pp. 21-31 ◽

Cited By ~ 60

Author(s):

Y. Fukazawa ◽

K. Makishima ◽

T. Tamura ◽

K. Nakazawa ◽

H. Ezawa ◽

...

Keyword(s):

Central Region ◽

Statistical Properties ◽

Intracluster Medium ◽

Metal Abundances

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A new and homogeneous metallicity scale for Galactic classical Cepheids

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833087 ◽

2018 ◽

Vol 616 ◽

pp. A82 ◽

Cited By ~ 3

Author(s):

B. Proxauf ◽

R. da Silva ◽

V. V. Kovtyukh ◽

G. Bono ◽

L. Inno ◽

...

Keyword(s):

Effective Temperature ◽

Signal To Noise Ratio ◽

High Signal ◽

Physical Parameters ◽

Classical Cepheids ◽

Microturbulent Velocity ◽

Metal Abundances ◽

Pulsation Cycle ◽

Intrinsic Error ◽

Better Than

We gathered more than 1130 high-resolution optical spectra for more than 250 Galactic classical Cepheids. The spectra were collected with the optical spectrographs UVES at VLT, HARPS at 3.6 m, FEROS at 2.2 m MPG/ESO, and STELLA. To improve the effective temperature estimates, we present more than 150 new line depth ratio (LDR) calibrations that together with similar calibrations already available in the literature allowed us to cover a broad range in wavelength (5348 ≤ λ ≤ 8427 Å) and in effective temperature (3500 ≤ Teff ≤ 7700 K). This gives us the unique opportunity to cover both the hottest and coolest phases along the Cepheid pulsation cycle and to limit the intrinsic error on individual measurements at the level of ~100 K. As a consequence of the high signal-to-noise ratio of individual spectra, we identified and measured hundreds of neutral and ionized lines of heavy elements, and in turn, have the opportunity to trace the variation of both surface gravity and microturbulent velocity along the pulsation cycle. The accuracy of the physical parameters and the number of Fe I (more than one hundred) and Fe II (more than ten) lines measured allowed us to estimate mean iron abundances with a precision better than 0.1 dex. We focus on 14 calibrating Cepheids for which the current spectra cover either the entire or a significant portion of the pulsation cycle. The current estimates of the variation of the physical parameters along the pulsation cycle and of the iron abundances agree very well with similar estimates available in the literature. Independent homogeneous estimates of both physical parameters and metal abundances based on different approaches that can constrain possible systematics are highly encouraged.

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