IR photometry and dust-shell models for two carbon starsстатья
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Дата последнего поиска статьи во внешних источниках: 22 апреля 2015 г.
Аннотация: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: tau V = 0.047. The dust shell of T Lyn is considerably hotter ( T 1 = 940 K), with tau V = 0.95. We estimate the mass-loss rate to be 1.8 × 10-7 M &sun;/year for ST And and 3.7 × 10-7 M &sun;/year for T Lyn.