COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1876

                                    Konkoly Observatory
                                    Budapest
                                    1980 December 5

                                    HU ISSN 0374-0676


  SPECTROSCOPIC MEASUREMENTS OF THE YELLOW SUPERGIANT CO Aur



CO Aur is a moderately bright (7.5m-8m) SRd or RV Tau star with
a spectral type of F5 Ib, as classified by Preston (Smak, 1964).
Photometry has been published by Kurochkin (1950), Smak (1964),
and Dawson (1979).
Since radial velocity observations of this kind of objects are
rare, this brighter object has been selected and observed spectroscopically 
in March and April, 1976. Eight spectra have been
taken with the Cassegrain spectrograph at the 106 cm telescope
of Hoher List Observatory. The dispersion was 47Ang./mm with a
spectral range from 3800 to 4800 Ang.. The results of the spectra
are summarized in Table I.

                    Table I

           JD     RV (km/s)     weight     Ca II emissions
       2442867.35  -25.2          7           weak
       2442869.35  -25.3         11        weak or absent
       2442874.35  -28.3         12        weak or absent
       2442877.35  -30.2         10          strong
       2442879.40  -24.5          7            ?
       2442886.40  -27.0          5            ?
       2442890.40  -25.4          5            ?
       2442891.40  -27.8          7        weak or absent

The mean error of the radial velocity determinations is 1.5 to
2.0 km/s. They are based exclusively on Fe lines. The radial
velocity zero point has not been calibrated during the observations, but 
earlier and later measurements showed systematical
displacements of the zero point of less than 1 km/s.
The amplitude of the variations is not improbable for stars
of this type (cf. Du Puy, 1973). The photometric measurements by
Smak show eight maxima within 120 days, so there was on the
average one maximum in 15 days. Within the 25 days of these

spectroscopic observations also two cycles are indicated. Ca II
emission is present in the spectra of CO Aur, but it is usually
weak. Only at the time of the most negative radial velocity measurement, 
an enhanced Ca II emission has been observed.







                       M. HOFFMANN

                   Observatorium Hoher List
                   5568 Daun / Eifel, BRD





References:
Dawson, D.W., 1979, Astrophys. J. Suppl. 41, 97 [BIBCODE 1979ApJS...41...97D ]
Du Puy, D.L., 1973, Astrophys. J. 185, 597 [BIBCODE 1973ApJ...185..597D ]
Kurochkin, N.E., 1950, Variable Stars (Russian) 7, 295
Smak, J., 1964, Publ.Astron.Soc. Pacific 76, 40 [BIBCODE 1964PASP...76...40S ]