Spectral Classification of Faint Carbon Stars

Eglitis, I.; Eglīte, M.; Balklavs, A.

doi:10.1515/astro-2017-0056

Cited by 2 publications

(2 citation statements)

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“…This star is 2MASS 20454509+4329181, also known as V2040 Cyg, and is referenced as a semi-regular pulsating carbon star in SIM-BAD (Aaronson et al 1990). A spectral type N5 was found for V2040 Cyg by Eglitis et al (2003). Its R and J magnitudes of 10.8 and 6.6, respectively, seem like a good match to the infrared magnitude m i of about 9 reported by Nassau & Blanco (1954).…”

Section: Early Type Stars: B and A Starssupporting

confidence: 71%

PALOMAR/TRIPLESPEC OBSERVATIONS OFSPITZER/MIPSGAL 24 μm CIRCUMSTELLAR SHELLS: UNVEILING THE NATURES OF THEIR CENTRAL SOURCES

Flagey

Noriega-Crespo

Petric

et al. 2014

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We present near-IR spectroscopic observations of the central sources in 17 circumstellar shells from a sample of more than 400 "bubbles" discovered in the Spitzer/MIPSGAL 24 µm survey of the Galactic plane and in the Cygnus-X region. To identify the natures of these shells, we have obtained J, H, and K band spectra with a resolution ∼2600 of the stars at their centers. We observed 14 MIPSGAL bubbles (MBs), WR149, and 2 objects in the Cygnus-X region (WR138a and BD+43 3710), our sample being about 2.5 magnitudes fainter in K band than previous studies of the central sources of MBs. We use spectroscopic diagnostics and spectral libraries of late and early type stars to constrain the natures of our targets. We find five late type giants. The equivalent widths of their CO 2.29 µm features allow us to determine the spectral types of the stars and hence derive extinction along the line of sight, distance, and physical size of the shells. We also find twelve early type stars, in nine MBs and the 3 comparison objects. We find that the subtype inferred from the near-IR for WR138a (WN9h) and WR149 (WN5h) agrees with that derived from optical observations. A careful analysis of the literature and the environment of BD+43 3710 allows us to rule out the carbon star interpretation previously suggested. Our near-IR spectrum suggests that it is a B5 supergiant. At the centers of the nine MBs, we find a WC5-6 star possibly of low-mass, a candidate O5-6 V star, a B0 supergiant, a B/A type giant, and five LBV candidates. We also report the detections of emission lines arising from at least two shells with typical extents (∼ 10 ′′ ) in agreement with those in the mid-IR. We summarize the findings on the natures of the MBs since their discovery, with 30% of them now known. Most MBs with central sources detected in the near-to mid-IR have been identified and are red and blue giants, supergiants, or stars evolving toward these phases including, in particular, a handful of newly discovered Wolf-Rayet stars and a significant number of LBV candidates.

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Section: Early Type Stars: B and A Starssupporting

confidence: 71%

PALOMAR/TRIPLESPEC OBSERVATIONS OFSPITZER/MIPSGAL 24 μm CIRCUMSTELLAR SHELLS: UNVEILING THE NATURES OF THEIR CENTRAL SOURCES

Flagey

Noriega-Crespo

Petric

et al. 2014

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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: 91%

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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Spectral Classification of Faint Carbon Stars

Abstract: Abstract. R{N classi cation of 187 faint carbon stars is based on the classical criteria adjusted to the yellow-red spectral region, with two new criteria added { the ratios of the red CN bands 6206/6332 ( A) and 6478/6631 ( A).

Cited by 2 publications

References 6 publications

PALOMAR/TRIPLESPEC OBSERVATIONS OFSPITZER/MIPSGAL 24 μm CIRCUMSTELLAR SHELLS: UNVEILING THE NATURES OF THEIR CENTRAL SOURCES

PALOMAR/TRIPLESPEC OBSERVATIONS OFSPITZER/MIPSGAL 24 μm CIRCUMSTELLAR SHELLS: UNVEILING THE NATURES OF THEIR CENTRAL SOURCES

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

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