Browsing by Subject "Binaire"

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    On the nature of the cool component of MWC 560
    (2007) Gromadzki, M; Mikołajewska, J; Whitelock, P A; Marang, F
    Context.MWC 560 (V694 Mon) is one of the most enigmatic symbiotic system with a very active accretion-powered hot component. Such activity can be supported only by a luminous asymptotic giant branch star, i.e. a Mira or SR variable, with a high mass-loss rate. It is also a very unusual jet source because the jet axis lies practically parallel to the line of sight. Aims. The aims of our study are the determination of the evolutionary status of the cool component of MWC 560. Methods. Our methods involve analysis of near-IR JHKL and optical light curves. Results. The cool component of MWC 560 pulsates with a period of ∼340 days, and it is probably a red SR variable on the thermally pulsing AGB. The high mass-loss rate expected for such a star is sufficient to power the observed activity of the hot companion.
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    The effect of dust obscuration in RR Telescopii on optical and IR long-term photometryand Fe II emission lines
    (2006) Kotnik-Karuza, D; Friedjung, M; Whitelock, P A; Marang, F; Exter, K; Keenan, F P; Pollacco, D L
    Aims. Infrared and optical photometric and spectroscopic observations of the symbiotic nova RR Tel are used to study the effects and properties of dust in symbiotic binaries containing a cool Mira component, as well as showing obscuration events of increased absorption, which are typical for such Miras. Methods. A set of photometric observations of the symbiotic nova RR Tel in different wavelength bands - visual from 1949 to 2002 and near-infrared (JHKL) from 1975 to 2002 - are presented. The variability due to the normal Mira pulsation was removed from the JHKL data, which were then compared with the American Association of Variable Star Observers' (AAVSO) visual light curve. The changes of the Fell emission line fluxes during the 1996-2000 obscuration episode were studied in the optical spectra taken with the Anglo-Australian telescope. Results. We discuss the three periods during which the Mira component was heavily obscured by dust as observed in the different wavelength bands. A change in the correlations of J with other infrared magnitudes was observed with the colour becoming redder alter JD 2 446 600. Generally, J-K was comparable, while K-L was larger than typical values for single Miras. A distance estimate of 2.5 kpc, based on the IR data, is given. A larger flux decrease for the permitted than for the forbidden Fe II lines, during the obscuration episode studied, has been found. There is no evidence for other correlations with line properties, in particular with wavelength, which suggests obscuration due to separate optically thick clouds in the outer layers. Conclusions.