AGB stars of the intermediate-age LMC cluster NGC 1846

Lebzelter, T.; Lederer, M.; Cristallo, S.; Hinkle, K. H.; Straniero, O.; Aringer, B.

doi:10.1051/0004-6361:200809363

Cited by 53 publications

(88 citation statements)

References 53 publications

(69 reference statements)

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“…Observational 12 C/ 13 C-values for AGB stars range from as low as 1 (Ohnaka & Tsuji 1999) up to about 90 (Milam et al 2009). Lebzelter et al (2008, and references therein) mention some clustering of empirical values of 12 C/ 13 C between 50 and 70 for galactic C-rich stars, while their evolutionary models even predict values higher than 100. The solar value is about 89 (Anders & Grevesse 1989).…”

Section: C/ 13 C Isotope Abundance Ratiomentioning

confidence: 99%

Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

Beck

Decin

Koter

et al. 2010

A&A

240

281

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Context. The evolution of intermediate and low-mass stars on the asymptotic giant branch is dominated by their strong dust-driven winds. More massive stars evolve into red supergiants with a similar envelope structure and strong wind. These stellar winds are a prime source for the chemical enrichment of the interstellar medium. Aims. We aim to (1) set up simple and general analytical expressions to estimate mass-loss rates of evolved stars, and (2) from those calculate estimates for the mass-loss rates of the asymptotic giant branch, red supergiant, and yellow hypergiant stars in our galactic sample. Methods. The rotationally excited lines of carbon monoxide (CO) are a classic and very robust diagnostic in the study of circumstellar envelopes. When sampling different layers of the circumstellar envelope, observations of these molecular lines lead to detailed profiles of kinetic temperature, expansion velocity, and density. A state-of-the-art, nonlocal thermal equilibrium, and co-moving frame radiative transfer code that predicts CO line intensities in the circumstellar envelopes of late-type stars is used in deriving relations between stellar and molecular-line parameters, on the one hand, and mass-loss rate, on the other. These expressions are applied to our extensive CO data set to estimate the mass-loss rates of 47 sample stars. Results. We present analytical expressions for estimating the mass-loss rates of evolved stellar objects for 8 rotational transitions of the CO molecule and thencompare our results to those of previous studies. Our expressions account for line saturation and resolving of the envelope, thereby allowing accurate determination of very high mass-loss rates. We argue that, for estimates based on a single rotational line, the CO(2-1) transition provides the most reliable mass-loss rate. The mass-loss rates calculated for the asympotic giant branch stars range from 4 × 10 −8 M yr −1 up to 8 × 10 −5 M yr −1 . For red supergiants they reach values between 2 × 10 −7 M yr −1 and 3 × 10 −4 M yr −1 . The estimates for the set of CO transitions allow time variability to be identified in the mass-loss rate. Possible mass-loss-rate variability is traced for 7 of the sample stars. We find a clear relation between the pulsation periods of the asympotic giant branch stars and their derived mass-loss rates, with a levelling off at ∼3 × 10 −5 M yr −1 for periods exceeding 850 days. Conclusions.

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Section: C/ 13 C Isotope Abundance Ratiomentioning

confidence: 99%

Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

Beck

Decin

Koter

et al. 2010

A&A

240

281

View full text Add to dashboard Cite

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“…For the model parameters we applied the values of Kipper (2004). Unfortunately, the molecular data in the line lists lack sufficient precision for this high resolution study, hence the synthetic spectrum differs strongly from the observations (see also the discussion in Lebzelter et al 2008;). …”

Section: Hd 134453 (X Tra)mentioning

confidence: 99%

Crires-Pop

Lebzelter

Seifahrt

Uttenthaler

et al. 2012

A&A

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Context. New instrumental capabilities and the wealth of astrophysical information extractable from the near-infrared wavelength region have led to a growing interest in the field of high resolution spectroscopy at 1-5 μm. Aims. We aim to provide a library of observed high-resolution and high signal-to-noise-ratio near-infrared spectra of stars of various types throughout the Hertzsprung-Russell diagram. This is needed for the exploration of spectral features in this wavelength range and for comparison of reference targets with observations and models. Methods. High quality spectra were obtained using the CRIRES near-infrared spectrograph at ESO's VLT covering the range from 0.97 μm to 5.3 μm at high spectral resolution. Accurate wavelength calibration and correction for telluric lines were performed by fitting synthetic transmission spectra for the Earth's atmosphere to each spectrum individually. Results. We describe the observational strategy and the current status and content of the library which includes 13 objects. The first examples of finally reduced spectra are presented. This publication will serve as a reference paper to introduce the library to the community and explore the extensive amount of material.

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“…While spectra of both oxygen and carbon rich stars were obtained, difficulties in modelling the C-stars lead to higher uncertainties for the abundances in these objects. A detailed description on data analysis, synthetic spectra calculation and abundance determination can be found in Lebzelter et al (2008).…”

Section: Observations and Abundance Determinationmentioning

confidence: 99%

“…More details on the findings for NGC 1846 have been published already in Lebzelter et al (2008). For the O-rich stars in NGC 1846 we determined C/O ratios between 0.2 and 0.65 with an uncertainty from ± 0.05 to ± 0.1 dex.…”

Section: Ngc 1846mentioning

confidence: 99%

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A study of AGB stars in LMC clusters

et al. 2008

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Abstract. LMC clusters offer an outstanding opportunity to investigate the late stages of stellar evolution of stars in the mass range between 1.5 and 2 M . In this presentation we will focus on our results on mixing events during the evolution along the Asymptotic Giant Branch (AGB). Surface abundances have been determined for a number of cluster AGB stars from high resolution near infrared spectra. We show for the first time the evolution of C/O and 12 C/ 13 C ratios along a cluster AGB. The change of both quantities due to dredge up events is compared with model predictions. Our results indicate the late occurrence of a moderate extra-mixing in some cases.

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AGB stars of the intermediate-age LMC cluster NGC 1846

Cited by 53 publications

References 53 publications

Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

Crires-Pop

A study of AGB stars in LMC clusters

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