WISE observations for the variety of Galactic carbon stars
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ORIGINAL ARTICLE
WISE observations for the variety of Galactic carbon stars P.S. Chen1
· J.Y. Liu1 · H.G. Shan1
Received: 17 January 2020 / Accepted: 17 September 2020 / Published online: 29 September 2020 © Springer Nature B.V. 2020
Abstract WISE observations of visual carbon stars (VCSs), infrared carbon stars (IRCSs), extreme carbon stars (ECSs), J-type carbon stars JCSs), and silicate carbon stars (SCSs) are presented in this paper. We found that in the WISE observational region carbon stars still form a sequence of VCSs → IRCSs → ECSs with the color gradually increasing. We also found that in the WISE two-color diagrams the JCS distribution is similar to that for the VCS, while the ECS distribution is similar to the IRCS. In addition, most of these carbon stars are around or on the lower right side of blackbody distributions in the WISE two-color diagrams due to the thermal radiation from dusty circumstellar envelopes, while some of them are around or on the upper left side of power law distributions possibly due to the radiation from dusty disks or showing the influence from some molecular features. Keywords Stars: AGB · Stars: carbon · Infrared: stars
1 Introduction It is well known that the evolution sequence from oxygenrich to carbon-rich stars was suggested for the asymptotic giant branch (AGB) phase (Iben and Renzini 1983; Willems and de Jong 1988; Chan and Kwok 1988, 1990). Now we Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10509-020-03872-9) contains supplementary material, which is available to authorized users.
B P.S. Chen
[email protected]
1
Yunnan Observatories and Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China
know that the spectral classes of M–S–C are indeed an evolutionary sequence for AGB stars with a low/moderate mass (Iben and Renzini 1983; Willems and de Jong 1988; Chan and Kwok 1988; Chen and Kwok 1993; Chen and Shan 2008). As in the last evolution stage, carbon stars play an important role in the AGB star evolution. The sequence of visual carbon stars (hereafter VCSs) → infrared carbon stars (hereafter IRCSs) → extreme carbon stars (hereafter ECSs) could be the evolutionary sequence during the carbon star phase (Chan and Kwok 1990; Volk et al. 1992, 2000; Chen and Kwok 1993; Yang et al. 2004; Speck et al. 2005; and Chen and Shan 2007). Because in all stages of the carbon star evolution a considerable part of energy is radiated in the infrared, an infrared study of the variety of carbon stars is very important, which is our purpose in this paper. In this paper we restrict our study to carbon stars in our Galaxy. In several of our previous papers we studied infrared properties for IRCSs (Chen and Shan 2008; Chen and Yang 2012), ECSs (Chen and Shan 2007) mainly by using 2MASS and IRAS data. We found that the infrared colors and temperatures of IRCSs are between those for VCSs and ECSs not only in the IRAS region but also in the nearinfrared region confirming t
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