Carbon and Oxygen Abundances Across the Hertzsprung Gap

Adamczak, Jens; Lambert, David L.

doi:10.1088/0004-637x/791/1/58

Cited by 15 publications

(11 citation statements)

References 58 publications

(69 reference statements)

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“…However, one exception is the recent extensive spectroscopic study of 188 Hertzsprung‐gap stars conducted by Adamczak & Lambert (), who concluded that their C and O abundances were almost similar to those of low mass dwarfs and no indication of significant mixing‐induced abundance changes was found. Therefore, their conclusion is in conflict with ours as well as those of other published work.…”

Section: Discussionmentioning

confidence: 99%

“…Comparison of the adopted stellar parameters and the resulting abundances in this study with those of Adamczak & Lambert (): (a) T eff , (b) log g , (c) v t , (d) v e sin i , (e) M , (f) [Fe/H], (g) [C/H], and (h) [O/H]…”

Section: Discussionmentioning

confidence: 99%

“…Besides, in our opinion, a weakpoint in their study is that they did not take into account N, which plays an important role in discussing the chemical anomaly due to mixing of H‐burning product because its abundance change is obviously large (compared to that of C or O). Accordingly, it seems still premature to regard the conclusion of Adamczak & Lambert () as being established, which would need to be checked by follow‐up investigations.…”

Section: Discussionmentioning

confidence: 99%

“…Takeda et al () carried out a comprehensive analysis of the C, N, O, and Na abundances of 12 Cepheid variables. Adamczak & Lambert () examined the C and O abundances for 188 stars across the Hertzsprung gap, which is probably the most extensive investigation as far as the number of sample stars is concerned. Molina & Rivera () reported the chemical abundances of many elements (including C, N, O, and Na) in 4 A–F supergiants.…”

Section: Introductionmentioning

confidence: 99%

“…In spite of these investigations, however, the picture of evolution‐induced chemical anomaly in this group of stars has not been clarified yet. Besides, targets in these past studies, except for Adamczak & Lambert (), appear to be biased toward comparatively slow rotators, despite rapid rotators are commonly included in this group of stars (presumably because of the growing difficulty in abundance determination).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Do Hertzsprung‐gap stars show any chemical anomaly?

2019

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With the aim of investigating how the surface abundances of intermediate‐mass stars off the main sequence (evolving toward the red‐giant stage) are affected by the evolution‐induced envelope mixing, we spectroscopically determined the abundances of Li, C, N, O, and Na for selected 62 late A through G subgiants, giants, and supergiants, which are often called “Hertzsprung‐gap stars,” by applying the synthetic spectrum‐fitting technique to Li i 6708, C i 5380, N i 7460, O i 6156–8, and Na i 6161 lines. A substantially large star‐to‐star dispersion (≳2 dex) was confirmed for the Li abundances, indicating that this vulnerable element can either suffer significant depletion before the red‐giant stage or almost retain the primordial composition. Regarding C, N, O, and Na possibly altered by dredge‐up of nuclear‐processed products, their abundances turned out to show considerable scatter. This suggests that these abundance results are likely to suffer appreciable uncertainties, the reason for which is not clear but might be due to some kind of inadequate modeling for the atmospheric structure. Yet, paying attention to the fact that the relative abundance ratios between C, N, and O should be more reliable (because systematic errors may be canceled as lines of similar properties are used for these species), we could confirm a positive correlation between [O/C] (ranging from ∼0 to ∼+0.5 dex) and [N/C] (showing a larger spread from ∼0 to ∼+1 dex), which is reasonably consistent with the theoretical prediction. This observational detection of C deficiency as well as N enrichment in our program stars manifestly indicates that the dredge‐up of H‐burning product can take place before entering the red‐giant stage, with its extent differing from star to star.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Do Hertzsprung‐gap stars show any chemical anomaly?

2019

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Classification and characterization using HCT/HFOSC spectra of carbon stars selected from the HES survey

Purandardas,

Goswami

2024

Astrophys Space Sci

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New determination of abundances and stellar parameters for a set of weakG-band stars

Jasniewicz

Masseron

Thévenin³

et al. 2016

A&A

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Context. Weak G-band (wGb) stars are a very peculiar class of red giants; they are almost devoided of carbon and often present mild lithium enrichment. Despite their very puzzling abundance patterns, very few detailed spectroscopic studies existed up to a few years ago, which prevented any clear understanding of the wGb phenomenon. We recently proposed the first consistent analysis of published data for a sample of 28 wGb stars and were able to identify them as descendants of early A-type to late B-type stars, although we were not able to conclude on their evolutionary status or the origin of their peculiar abundance pattern. Aims. Using new high-resolution spectra, we present the study of a new sample of wGb stars with the aim of homogeneously deriving their fundamental parameters and surface abundances for a selected set of chemical species that we use to improve our insight on this peculiar class of objects. Methods. We obtained high-resolution and high signal-to-noise spectra for 19 wGb stars in the southern and northern hemisphere that we used to perform consistent spectral synthesis to derive their fundamental parameters and metallicities, as well as the spectroscopic abundances for Li, C, 12 C/ 13 C, N, O, Na, Sr, and Ba. We also computed dedicated stellar evolution models that we used to determine the masses and to investigate the evolutionary status and chemical history of the stars in our sample. Results. We confirm that the wGb stars are stars with initial masses in the range 3.2 to 4.2 M . We suggest that a large fraction could be mildly evolved stars on the subgiant branch currently undergoing the first dredge-up, while a smaller number of stars are more probably in the core He burning phase at the clump. After analysing their abundance pattern, we confirm their strong nitrogen enrichment anti-correlated with large carbon depletion, characteristic of material fully processed through the CNO cycle to an extent not known in evolved intermediate-mass stars in the field and in open clusters. However, we demonstrate here that such a pattern is very unlikely owing to self-enrichment. Conclusions. In the light of the current observational constraints, no solid self-consistent pollution scenario can be presented either, leaving the wGb puzzle largely unsolved.

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Carbon and Oxygen Abundances Across the Hertzsprung Gap

Cited by 15 publications

References 58 publications

Do Hertzsprung‐gap stars show any chemical anomaly?

Do Hertzsprung‐gap stars show any chemical anomaly?

Classification and characterization using HCT/HFOSC spectra of carbon stars selected from the HES survey

New determination of abundances and stellar parameters for a set of weakG-band stars

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