Experimental Ca I oscillator strengths for the 4p–5s triplet

Aldenius, Maria; Lundberg, Hans; Blackwell-Whitehead, Richard

doi:10.1051/0004-6361/200911844

Cited by 26 publications

(12 citation statements)

References 30 publications

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“…Seven lines from three multiplets are easily measurable. Ca: The gf values for the 13 Ca i lines in Table 3 are taken from the NIST data base. New measurements for RMT 3 by Aldenius, Lundberg & Blackwell‐Whitehead (2009) are smaller by only 0.07 dex, a difference that is ignored here. Fig.…”

Section: Abundance Analysis – Elements and Linesmentioning

confidence: 93%

High-resolution optical spectroscopy of the F supergiant protoplanetary nebula IRAS 18095+2704

Şahìn

Lambert

Клочкова

et al. 2010

Monthly Notices of the Royal Astronomical Society

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An abundance analysis is presented for IRAS 18095+2704 (V887 Her), a post‐asymptotic giant branch star and protoplanetary nebula. The analysis is based on high‐resolution optical spectra from the McDonald Observatory and the Special Astrophysical Observatory. Standard analysis using a classical Kurucz model atmosphere and the line analysis program moog provides the atmospheric parameters: Teff= 6500 K, log g=+0.5, microturbulent velocity ξ= 4.7 km s−1 and [Fe/H]=−0.9. Extraction of these parameters is based on excitation of Fe i lines, ionization equilibrium between neutral and ions of Mg, Ca, Ti, Cr and Fe, and the wings of hydrogen Paschen lines. Elemental abundances are obtained for 22 elements and upper limits for an additional four elements. These results show that the star's atmosphere has not experienced a significant number of C‐ and s‐process enriching thermal pulses. Abundance anomalies as judged relative to the compositions of unevolved and less‐evolved normal stars of a similar metallicity include Al, Y and Zr deficiencies with respect to Fe of about 0.5 dex. Judged by composition, the star resembles an RV Tauri variable that has been mildly affected by dust–gas separation reducing the abundances of the elements of highest condensation temperature. This separation may occur in the stellar wind. There are indications that the standard one‐dimensional local thermodynamic equilibrium analysis is not entirely appropriate for IRAS 18095+2704. These include a supersonic macroturbulent velocity of 23 km s−1, emission in Hα and the failure of predicted profiles to fit observed profiles of Hβ and Hγ.

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Section: Abundance Analysis – Elements and Linesmentioning

confidence: 93%

High-resolution optical spectroscopy of the F supergiant protoplanetary nebula IRAS 18095+2704

Şahìn

Lambert

Клочкова

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…Ba (Z = 56) is enhanced by ≈ 0.3 dex relative to the template for the main component of the r-process when normalized to Eu. Sr,Y,Zr,and Mo (Z = 38,39,40,and 42,respectively) are enhanced by ≈ 0.9, 0.5, 0.9, and 0.6 dex. hancement of other elements with a substantial s-process component in solar system material, such as Yb,Hf,and Pb (Z = 70,72,and 82).…”

Section: Lithium Through Siliconmentioning

confidence: 99%

Detailed abundances of 15 stars in the metal-poor globular cluster NGC 4833★

Roederer

Thompson

2015

Monthly Notices of the Royal Astronomical Society

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We have observed 15 red giant stars in the relatively massive, metal-poor globular cluster NGC 4833 using the MIKE spectrograph at Magellan. We calculate stellar parameters for each star and perform a standard abundance analysis to derive abundances of 43 species of 39 elements, including 20 elements heavier than the iron group. We derive [Fe/H] = −2.25 ± 0.02 from Fe i lines and [Fe/H] = −2.19 ± 0.013 from Fe ii lines. We confirm earlier results that found no internal metallicity spread in NGC 4833, and there are no significant star-to-star abundance dispersions among any elements in the iron group (19 Z 30). We recover the usual abundance variations among the light elements C, N, O, Na, Mg, Al, and possibly Si. The heavy-element distribution reflects enrichment by r-process nucleosynthesis ([Eu/Fe] = +0.36 ± 0.03), as found in many other metal-poor globular clusters. We investigate small star-to-star variations found among the neutron-capture elements, and we conclude that these are probably not real variations. Upper limits on the Th abundance, log ǫ (Th/Eu) < −0.47 ± 0.09, indicate that NGC 4833, like other globular clusters where Th has been studied, did not experience a so-called "actinide boost."

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“…The atomic data for the Ca i lines are taken from Smith & Raggett (1981), apart from the log g f values for Ca i 612.2 and 616.2 nm, which are from Aldenius et al (2009).…”

Section: Linelist and Analysis Toolmentioning

confidence: 99%

Determination of robust metallicities for metal-rich red giant branch stars

Liu

Ruchti

Feltzing

et al. 2017

A&A

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Context. The study of the Milky Way relies on our ability to interpret the light from stars correctly. With the advent of the astrometric ESA mission Gaia we will enter a new era where the study of the Milky Way can be undertaken on much larger scales than currently possible. In particular we will be able to obtain full 3D space motions of red giant stars at large distances. This calls for a reinvestigation of how reliably we can determine, e.g., iron abundances in such stars and how well they reproduce those of dwarf stars. Aims. Here we explore robust ways to determine the iron content of metal-rich giant stars. We aim to understand what biases and shortcomings widely applied methods suffer from. Methods. In this study we are mainly concerned with standard methods to analyse stellar spectra. This includes the analysis of individual lines to determine stellar parameters, analysis of the broad wings of certain lines (e.g., Hα and calcium lines) to determine effective temperature and surface gravity for the stars. Results. For NGC 6528 we find that [Fe/H] = +0.04 dex with a scatter of σ = 0.07 dex, which gives an error in the derived mean abundance of 0.02 dex. Conclusions. Our work has two important conclusions for analysis of metal-rich red giant branch stars. 1) For spectra with S/N below about 35 per reduced pixel [Fe/H] become too high, 2) Determination of T eff using the wings of the Hα line results in [Fe/H] values about 0.1 dex higher than if excitational equilibrium is used. The last conclusion is perhaps not surprising as we expect NLTE effect to become more prominent in cooler stars and we can not use the the wings of the Hα line to determine T eff for the cool stars in our sample. We therefore recommend that in studies of metal-rich red giant stars care needs to be taken to obtain sufficient calibration data in order to be able to also use the cooler stars.

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Experimental Ca I oscillator strengths for the 4p–5s triplet

Cited by 26 publications

References 30 publications

High-resolution optical spectroscopy of the F supergiant protoplanetary nebula IRAS 18095+2704

High-resolution optical spectroscopy of the F supergiant protoplanetary nebula IRAS 18095+2704

Detailed abundances of 15 stars in the metal-poor globular cluster NGC 4833★

Determination of robust metallicities for metal-rich red giant branch stars

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