Variability of ultraviolet emission in the carbon star TX PISCIUM

Johnson, H. R.; Baumert, J. H.; Querci, F.; Querci, M.

doi:10.1086/164833

Cited by 21 publications

(12 citation statements)

References 0 publications

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“…Our study corroborates the model proposed by Johnson et al (1988) based on the binary hypothesis (red giant primary plus small hot companion) to account for the properties of the IUE UV spectrum. Like for the three red giants studied in the previous paper of this series (Prieur, Carquillat & Griffin 2006), we will assume M 1 ≈ 2.5 M which can be considered as a typical value for a red giant.…”

Section: Hd 59643 (Hip 36623 Nq Gem)supporting

confidence: 90%

Contribution to the study of F‐G‐K‐M binaries: XII. Orbital elements of seven new spectroscopic binaries

Carquillat¹,

Prieur²

2008

Astron Nachr

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International audienceThe orbital elements of seven single-lined spectroscopic binaries, HD 31855, HD 59643, HD 60092, HD 133189, HD 162262, HD 203522, BD +43o 1331 are presented. They are obtained from observations made with two photoelectric spectrometers of CORAVEL type, the first located at the Observatoire de Haute-Provence and the second at the Cambridge Observatories. From those orbital elements and other data available in the literature, we deduce some information about the unseen companions and their separations with respect to the primaries. We then discuss the rotation-revolution synchronism and conclude that some of those stars have probably reached the state of (pseudo-)synchronism. Finally we give a synopsis of the results obtained in this series of papers. Our radial velocity monitoring of more than three decades has allowed us to derive accurate orbital elements of 35 spectroscopic binaries, with a cool primary star of type F-G-K-M. The corresponding range of periods varies from a few days to more than 10 years

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Section: Hd 59643 (Hip 36623 Nq Gem)supporting

confidence: 90%

Contribution to the study of F‐G‐K‐M binaries: XII. Orbital elements of seven new spectroscopic binaries

Carquillat¹,

Prieur²

2008

Astron Nachr

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“…Among the late-R stars we have two peculiar stars. HIP 36 623 is a symbiotic star (Johnson et al 1988;Belczyński et al 2000;Munari & Zwitter 2002) whose luminosity (see Table 2) and chemical composition (see Tables 5 and 6) are compatible with those expected at the AGB phase. Perhaps the envelope of this star has undergone two periods of mixing: the first one by the material accreted from the primary star, and the second one, a self-contamination triggered by third dredge-up episodes in the AGB phase.…”

Section: Comments On Particular Starsmentioning

confidence: 53%

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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“…We therefore include this object as suspected symbiotic. s07=NQ Gem Suspected in [120]. Highly variable UV continuum with strong [302] and UV excess.…”

Section: =R Aqrmentioning

confidence: 99%

A catalogue of symbiotic stars

Belczyński

Mikołajewska

Munari

et al. 2000

Astron. Astrophys. Suppl. Ser.

378

407

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Abstract. We present a new catalogue of symbiotic stars. In our list we include 188 symbiotic stars as well as 30 objects suspected of being symbiotic. For each star, we present basic observational material: coordinates, V and K magnitudes, ultraviolet (UV), infrared (IR), X-ray and radio observations. We also list the spectral type of the cool component, the maximum ionization potential observed, references to finding charts, spectra, classifications and recent papers discussing the physical parameters and nature of each object. Moreover, we present the orbital photometric ephemerides and orbital elements of known symbiotic binaries, pulsational periods for symbiotic Miras, Hipparcos parallaxes and information about outbursts and flickering.

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Variability of ultraviolet emission in the carbon star TX PISCIUM

Cited by 21 publications

References 0 publications

Contribution to the study of F‐G‐K‐M binaries: XII. Orbital elements of seven new spectroscopic binaries

Contribution to the study of F‐G‐K‐M binaries: XII. Orbital elements of seven new spectroscopic binaries

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

A catalogue of symbiotic stars

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