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Analysis of near infrared observations of the symbiotic mira RR Tel

JHKL photometry of the symbiotic Mira RR Tel over 25 years shows variable fading in all bands which has been explained by obscuration due to dust as a result of the symbiotic nature of this binary. The evolutionary track (time changes) of the star has been presented in two-colour diagrams together with the corresponding mean values of normal Miras with thick and thin dust shells and pulsation periods between 350 and 600 days. The observed RR Tel infrared colours are significantly shifted out of the range shown by normal unreddened Miras. The distance of RR Tel has been estimated by use of the colour correlation line before obscuration and its extrapolation to the thin shell Mira distribution for a small Ak absorption. The dust temperature has been calculated by a simplified two-blackbodies model, neglecting the presence of the hot companion as well as the complexity of the interaction between the two stars, leading to a very little dust emission even at the longest near IR wavelengths and hence to the predominant influence of reddening on the observed colours. The contribution of other non Mira sources of radiation to the infrared magnitudes is discussed.

RR Tel; symbiotic miras; dust; IR photometry; model

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