IR photometry and dust-shell models for two carbon stars
We present JHKLM photometry of the carbon stars ST And and T Lyn acquired in 2000–2010. Along with brightness variations due to pulsations, changes on timescales of 2000–3000 days are also observed. Our combined light curves can be satisfactorily represented with light elements derived from visual observations, but the maxima are delayed relative to the calculated times. A color-index analysis demonstrates that the dust shell of ST And is fairly weak, and is manifest only episodically, while the presence of hot dust was always detected for T Lyn. These results confirm models of spherically symmetric stellar dust shells based on mean-flux data, supplemented with observations in the intermediate IR from the IRAS and AKARI satellites. The visual optical depth of the relatively cool dust shell of ST And assuming a dust temperature at the inner edge of T 1 = 510 K is very low: τ V = 0.047. The dust shell of T Lyn is considerably hotter (T 1 = 940 K), with τ V = 0.95. We estimate the mass-loss rate to be 1.8 × 10−7 M ⊙/year for ST And and 3.7 × 10−7 M ⊙/year for T Lyn.
KeywordsAstronomy Report Light Curf Color Index Stellar Wind Brightness Variation
Unable to display preview. Download preview PDF.
- 1.N. N. Samus, O. V. Durlevich, et al., General Catalogue of Variable Stars, VizieR On-line Data Catalog: B/gcvs (2009).Google Scholar
- 13.IRAS Catalogs and Atlases Explanatory Supplement, NASA RP-1190, vol. 1, Ed. by C. Beichman, G. Neugebauer, H. J. Habing, et al. (GPO, Washington, DC, 1988).Google Scholar
- 19.J. S. Mathis, W. Rumpl, and K. H. Nordsieck, Astrophys. J. 17, 25 (1977).Google Scholar