Astron. Astrophys. 323, 387-392 (1997)

5. Conclusions

The outburst of RR Tel began in October 1944. The nova event led to an extended atmosphere with a radius of , but without noticeable mass-loss. The transition to the nebular phase began between May and August 1949. It led to a small and hot radiative core. It was accompanied by growing mass-loss. The corresponding wind had terminal velocities of km/s in October 1949, increasing to km/s in 1960. After 1960 the wind diminishes, and from 1978 onward there is no trace of mass-loss. By 1960 the outbursting star had reached K. After 1960 it evolved at approximately constant effective temperature but decreasing luminosity. When in 1978 IUE began to take high resolution spectra, evidence for a fast and significant stellar wind had disappeared. The observations of HST in 1995 confirm that result.

From a combination of HST, HUT, and ORFEUS observations we see that from 930 Å to 1400 Å the observed, de-reddened continuum can be well fitted with a black-body emission of K and , corresponding to a hot star with . At wavelengths the nebular emission increasingly dominates the continuum.

Jordan et al. (1994) attribute the X-ray flux of RR Tel in 1992 mainly to a stellar atmosphere of K and . In addition they postulate a hot low luminosity plasma () of several K, which could be due to a mass-loss wind of /yr and km/s. That wind would be too low to be detected by our observations.- The relative C/N/O abundances found by Nussbaumer et al. (1988) are not nova-like, and they are consistent with little contamination of the nebula by nova-processed matter.

For AG Peg, the oldest still active symbiotic nova, Vogel & Nussbaumer (1994) find during a very active phase a mass-loss rate of . If we generously credit RR Tel with a similar wind for the period of 1950 to 1960, we arrive at a total mass-loss of . The lowest total accreted mass listed by Prialnik & Kovetz (1995) for candidates of symbiotic novae is . Thus, RR Tel will probably retain most of its formerly accreted mass.

The key to an estimate of the total mass-loss of RR Tel lies in the spectra taken between 1949 and 1960. It would be of great value if they were re-analyzed. A mass-loss analysis would require the visual magnitude, and equivalent widths and profiles of He I and He II wind lines.

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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