COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1387

                                   Konkoly Observatory
                                   Budapest
                                   1978 February 13



    LIGHT VARIATIONS OF THE H AND K EMISSION STAR HD 206860



      HD 206860 is a G0V star showing H and K emission core.
Spectrophotometric observations by O.C.Wilson (1976) show small
amplitude but definite variations of the H and K emission components 
indicating a chromospheric activity. No clear periodicity
results from Wilson's observations carried out between 1967 and
1975.                                                
      In the framework of a research of photospheric activity
in stars showing a chromospheric activity (Blanco and Catalano
1970; Blanco, Catalano and Godoli 1973), UBV observations of HD
206860 were made at the stellar station of Catania Astrophysical
Observatory. The observations were performed with the 30 cm N
cassegrain telescope in the years 1970, 1971, 1972 and with the 61
cm cassegrain telescope in the years 1974, 1975, 1977. The stars
HD 207223, HD 212314 and HD 211976, whose UBV magnitudes were
taken from the Photoelectric Catalogue (Blanco et al. 1968), 
allow us to transform our observations to the UBV standard system.
A total of 428 measurements for each colour were obtained in 96
nights of observation. The V light measurements showed small
amplitude variations. An analysis for periodicity was made using
a computer programme which picks out the period minimizing the
root mean square of the scatter along the light curve. We found
a period of 24.90d and an amplitude of 0.02m in the V light. No
variation is evident for the colour indices B-V and U-B. The V
magnitude and colour indices versus the phase computed by the
elements:

         JD_hel (the light min.)=2440821.48 +- 24.90d E

                       [FIGURE 1]

are plotted in the figure. Even if the variation amplitude is of
the same order as the scatter of the observations, the V light
curve repeats unchanged during the seven years of observations.
The annual average of V magnitude and colour indices do not show
any clear variation and give mean values of V = 5.944 +- 0.008,
B-V = 0.589m +- 0.013, U-B = 0.035m +- 0.014.
      HD 206860 is known to be a single star, so the variations
we observed are due to an intrinsic variability. We would like to
interpret the light variations in terms of spots, or more generally 
active regions, connected with the observed chromospheric activity. 
In this hypothesis the observed period of 24.90d would be the
rotation period of the star, which applies very well to a G0 main
sequence star.




                  C. BLANCO, S. CATALANO, E. MARILLI

                     Osservatorio Astrofisico
                     citta universitaria
                     95125 Catania-Italia

                     Istituto di Astronomia
                     citta universitaria
                     95925 Catania-Italia





References:

Blanco C., Catalano S. 1970, Publ.Astron.Soc,Pacific 82, 1293. [BIBCODE 1970PASP...82.1293B ]
Blanco C., Catalano S., Godoli G.  1972, Mem.Soc.Astron.Ital.  43, 663. [BIBCODE 1972MmSAI..43..663B ]
Blanco V., Demers S., Douglass G.G., Fitzgerald M.P.  1968, Publ.
    U.S.Naval Obs. 21. [BIBCODE 1968PUSNO..21....1B ]
Wilson O.C. 1976, in Basic Mechanics of Solar Activity, Eds.
    Bumba and Kleczek, p. 447. [BIBCODE 1976IAUS...71..447W ]