A. Salama 1, K. Leech 1, S. P. S. Eyres 2, & A. Evans 2
1 Vilspa
2 Keele University
Symbiotic stars are a heterogeneous group of binary stars (see `The Symbiotic Stars', Kenyon). They are defined on the basis of their optical spectra, which show evidence of a cool (red giant or Mira) continuum on which are superimposed numerous strong, high excitation emission lines. RR Tel is the proto-type of a sub-class of symbiotic stars known as `symbiotic novae' or `very slow novae', because they have shown evidence in the past of nova-like outbursts; in the case of RR Tel this occurred in 1947. It is also classified as a `D-type' symbiotic, because the near-infrared emission is dominated by circumstellar dust.
The cool component in RR Tel is a Mira variable, in which steam has been
detected at 2 microns. RR Tel was observed by the IRAS LRS; the LRS
spectrum, although noisy, clearly shows the 9.7 and 18 micron `silicate'
features. X-ray observations have revealed the properties of the hot
source responsible for the high excitation emission
(
,
,
log g = 6.5) and
of the line emitting region. Hayes &
Nussbaumer (AA, 161, 287) have confirmed that the nebular emission
associated with RR Tel is radiatively ionized and collisioanlly excited.
It has long been known that RR Tel has a rich emission line spectrum, and this has been extensively studied at optical and ultraviolet wavelengths. The far infrared is essentially the last part of the emission line spectrum of RR Tel which remains unobserved. We describe here an observation of RR Tel with the SWS and LWS. Our data confirm the silicate features, and are of such quality that the mineralogy of the silicate can be determined. We also use CLOUDY to model the IR line emission.