An atlas of high resolution line profiles of symbiotic stars. I. Coude echelle spectrometry of southern objects and a classification system of H-alpha line profile.
Emission lines of 59 southern symbiotic and related stars were observed on 194 spectra taken with the Coudé Echelle Spectrometer attached to the 1.4 m Coudé Auxiliary Telescope of the European Southern Observatory. On the basis of multiple Gaussian fits to emission and absorption components of the Hα line profile, the starlike (S) and dusty (D) symbiotics are each classified into three spectroscopic subtypes. Subtype S-1 shows a fairly narrow emission profile with no prominent absorption, S-2 shows a clear absorption feature superimposed on the broad emission, S-3 has a strong absorption feature which reaches at least to the continuum level. Radial velocities of the central emission component are generally redshifted as compared to those of the optically thin nebular lines. This indicates that the blue wing of the emission is weakened by an overlying absorption component caused by a massive wind. Among the 8 objects of subtype S-3 are the five known recurrent novae with giant companions and two symbiotic stars, PU Vul and AS 296, which are undergoing prolonged outbursts. Objects of subtype D-1 show a strong, narrow Hα emission profile, those of D-2 a slightly asymmetric profile with a prominent emission component on the blueward side of Hα, which in most cases can be attributed to He II 6560, those of D-3 have a broad profile with a central absorption feature. The morphological classification of the S and D subtypes corresponds to a physical classification in terms of a wind model. In S-type symbiotics, wind strength increases, and wind velocity decreases with increasing subtype. In types D-1 and D-2 the Hα line originates in a tenuous nebula, while the wind in the D-3 subtype is slow and very massive, as it is in S-3. The generally large radial velocity dispersions indicate membership of the majority of symbiotic stars in the old disc or halo population. The objects with the smallest velocity dispersion are those of subtypes S-3 and D-3. These presumably youngest symbiotics show the largest mass loss rates and the smallest wind velocities.
Astronomy and Astrophysics Supplement Series
- Pub Date:
- December 1993
- binaries: close;
- stars: novae;