Kinematics of 11 Bidelman's weak‐lined stars

Bartkevicius, A.; Sperauskas, J.

doi:10.1002/asna.200310151

Cited by 15 publications

(21 citation statements)

References 15 publications

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“…3). We will see that an effective temperature threshold Barnbaum et al (1996); 2: Bartkevicius (1996); 3: Eglitis et al (2003); 4: Keenan (1993); 5: Keenan & Morgan (1941); 6: Lee & Bartlett (1944);7: McClure (1970); 8: Morgan & Keenan (1973);9: Sanford (1944); 10: Schild (1973);11: Schmitt (1971);12: Shane (1928); 13: Stock & Welhau (1956);14: Upgren (1962);15: Vandervort (1958);16: Yamashita (1972);17: Yamashita (1975). The following stars show evidence of binarity: HIP 36 623 (Carquillat & Prieur 2008), HIP 109 158 (Makarov & Kaplan 2005), HIP 53 832 (Platais et al 2003) andHIP 85 750 (McClure 1997). of ∼3600 K seems to be a good criterion to distinguish between early-and late-R stars.…”

Section: Spectral Classificationmentioning

confidence: 89%

The chemical composition of carbon stars. The R-type stars

Zamora¹,

Abia²,

Plez

et al. 2009

A&A

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Aims. The aim of this work is to shed some light on the problem of the formation of carbon stars of R-type from a detailed study of their chemical composition.Methods. We use high-resolution and high signal-to-noise optical spectra of 23 R-type stars (both early-and late-types) selected from the Hipparcos catalogue. The chemical analysis is made using spectral synthesis in LTE and state-of-the-art carbon-rich spherical model atmospheres. We derive their CNO content (including the 12 C/ 13 C ratio), average metallicity, lithium, and light (Sr, Y, Zr) and heavy (Ba, La, Nd, Sm) s-element abundances. The observed properties of the stars (galactic distribution, kinematics, binarity, photometry and luminosity) are also discussed. Results. Our analysis shows that late-R stars are carbon stars with identical chemical and observational characteristics as the normal (N-type) AGB carbon stars. The s-element abundance pattern derived can be reproduced by low-mass AGB nucleosynthesis models where the 13 C(α, n) 16 O reaction is the main neutron donor. We confirm the results of the sole previous abundance analysis of early-R stars, namely that they are carbon stars with near solar metallicity showing enhanced nitrogen, low 12 C/ 13 C ratios and no s-element enhancements. In addition, we have found that early-R stars have Li abundances larger than expected for post RGB tip giants. We also find that a significant number (∼40%) of the early-R stars in our sample are wrongly classified, probably being classical CH stars and normal K giants. Conclusions. On the basis of the chemical analysis, we confirm the previous suggestion that late-R stars are just misclassified N-type carbon stars in the AGB phase of evolution. Their photometric, kinematic, variability and luminosity properties are also compatible with this. In consequence, we suggest that the number of true R stars is considerably lower than previously believed. This alleviates the problem of considering R stars as a frequent stage in the evolution of low-mass stars. We briefly discuss the different scenarios proposed for the formation of early-R stars. The mixing of carbon during an anomalous He-flash is favoured, although no physical mechanism able to trigger that mixing has been found yet. The origin of these stars still remains a mystery.

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Section: Spectral Classificationmentioning

confidence: 89%

The chemical composition of carbon stars. The R-type stars

Zamora¹,

Abia²,

Plez

et al. 2009

A&A

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“…-UU Her-type stars -UU Her in the catalogue. Among Population II supergiants, there is a small group of variable stars called UU Her after the best studied member of this group 3 (Sasselov 1984;Bartkevičius 1992). The characteristic criteria of UU Her-type stars, in addition to the general hglsg properties, include high radial velocities, small amplitude pulsations (of order of 0.1 mag) and large IR excess due to circumstellar dust.…”

Section: Classification Criteriamentioning

confidence: 99%

“…The characteristic criteria of UU Her-type stars, in addition to the general hglsg properties, include high radial velocities, small amplitude pulsations (of order of 0.1 mag) and large IR excess due to circumstellar dust. Bartkevičius (1992) collected the available information on 18 UU Her-type stars, and we classified 12 of them as very likely post-AGB, three as possible post-AGB and three are disqualified in our catalogue. The PS Gem is not in the Bartkevičius (1992) list, but the object is classified in the literature as UU Her-type as well.…”

Section: Classification Criteriamentioning

confidence: 99%

An evolutionary catalogue of galactic post-AGB and related objects

Szczerba¹,

Siódmiak

Stasińska

et al. 2007

A&A

132

169

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Aims. With the ongoing AKARI infrared sky survey, of much greater sensitivity than IRAS, a wealth of post-AGB objects may be discovered. It is thus time to organize our present knowledge of known post-AGB stars in the galaxy with a view to using it to search for new post-AGB objects among AKARI sources. Methods. We searched the literature available on the NASA Astrophysics Data System up to 1 October 2006, and defined criteria for classifying sources into three categories: very likely, possible and disqualified post-AGB objects. The category of very likely post-AGB objects is made up of several classes. Results. We have created an evolutionary, on-line catalogue of Galactic post-AGB objects, to be referred to as the Toruń catalogue of Galactic post-AGB and related objects. The present version of the catalogue contains 326 very likely, 107 possible and 64 disqualified objects. For the very likely post-AGB objects, the catalogue gives the available optical and infrared photometry, infrared spectroscopy and spectral types, and links to finding charts and bibliography.

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“…While we have not observed the G-band of this star, we might predict that #6007741 should have a rather strong G-band, and should then be classified as a mild CH-star. Ba and CH-stars are rare in globular clusters (for a catalogue, see Bartkevicius 1996). Most of them are in GCs of low central concentration.…”

Section: The Ba-star #6007741mentioning

confidence: 99%

Na-O anticorrelation and horizontal branches

Gratton¹,

Lucatello²,

Bragaglia

et al. 2007

A&A

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Aims. We present an analysis of FLAMES-Giraffe spectra for several bright giants in NGC 6441, to investigate the presence and extent of the Na-O anticorrelation in this anomalous globular cluster. Methods. The field of NGC 6441 is very crowded, with severe contamination by foreground (mainly bulge) field stars. Appropriate membership criteria were devised to identify a group of 25 likely cluster members among the about 130 stars observed. Combined with the UVES data obtained with the same observations , high dispersion abundance analyses are now available for a total of 30 stars in NGC 6441, 29 of them having data for both O and Na. The spectra were analyzed by a standard line analysis procedure; care was taken to minimize the impact of the differential interstellar reddening throughout the cluster, and to extract reliable information from crowded, and moderately high S/N (30-70), moderately high resolution (R ∼ 23 000) spectra. Results. NGC 6441 has the typical abundance pattern seen in several other globular clusters. It is very metal-rich ([Fe/H] = −0.34 ± 0.02 ± 0.04 dex). There is no clear sign of star-to-star scatter in the Fe-peak elements. The α-elements Mg, Si, Ca, and Ti are overabundant by rather large factors, suggesting that the cluster formed from material enriched by massive core collapse SNe. The O-Na anticorrelation is well defined, with about 1/4 of the stars being Na-rich and O-poor. One of the stars is a Ba-rich and moderately C-rich star. Such stars are rare in globular clusters. Conclusions. The distribution of [Na/O] ratios among RGB stars in NGC 6441 appears similar to the distribution of colors of stars along the horizontal branch. The fraction of Na-poor, O-rich stars found in NGC 6441 agrees well with that of stars on the red horizontal branch of this cluster (in both cases about 80%), with a sloping distribution toward lower values of [O/Na] (among RGB stars) and bluer colors (among HB stars).

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Kinematics of 11 Bidelman's weak‐lined stars

Cited by 15 publications

References 15 publications

The chemical composition of carbon stars. The R-type stars

The chemical composition of carbon stars. The R-type stars

An evolutionary catalogue of galactic post-AGB and related objects

Na-O anticorrelation and horizontal branches

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