COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 2390

                                     Konkoly Observatory
                                     Budapest
                                     25 August 1983

                                     HU ISSN 0374-0676


               PHOTOMETRY  OF FK COMAE


   The 8th magnitude star FK Com (BD+24d2592) is the prototype
of the small group of single, fast rotating giants of late spectral 
type. It was first observed photometrically by Chugainov
(1976) and later investigated by Rucinski (1981). In this paper
we present new observations of FK Com, obtained during 12 nights
in May and June 1982.
   The observations of FK Com were made using a single channel
photometer with the 60 cm Cassegrain telescope at Ostrowik station 
of Warsaw University Observatory, equipped with an uncooled
EMI 6256 A photomultiplier. The variable was monitored through
the B and V filters. BD +24d2593 with magnitudes V = 7.621 and
B - V = 0.427 (Rucinski, 1981) served as the comparison star and
BD +25d2643 with V = 6.091 and B - V = 0.959 (Rucinski, 1981) as
the supplementary comparison. The absolute photometry of the
comparison star was not done, but the stability of BD +24d2593
relative to BD +25d2643 was better than 0.01 mag during the period
of the observations.
   Table I lists all our data. The first and second columns give
heliocentric julian day and phase, two next columns - differences
DeltaV and Delta(B-V) in the sense variable minus comparison. The values
in third and fourth columns are the mean values of several readings 
in interval less than 0.05 of the period. The accuracy of
each averaged observation is about 0.010 and 0.015 in B-V and V
respectively.
  Figure 1 shows the V and B-V light curves constructed using
data from Table I and the ephemeris given by Chugainov (1976):

             JD_Hel = 2442192.345 + 2.400d E

The V light curve obtained by us is quite similar to that of
Rucinski (1981): maximum light in phase 0.4 - 0.5 and steeper
declining branch than the rising one characterize this light


              Table I
     The observations of FK Com
-------------------------------------
Hel. J.D.   Phase  DeltaV  Delta(B-V)
2440000+
-------------------------------------
5116.454    0.379   0.541    0.363
5117.440    0.790   0.616    0.390
5119.423    0.616   0.560    0.377
5119.503    0.649   0.576    0.385
5120.428    0.035   0.626    0.394
5121.446    0.459   0.540    0.365
5122.437    0.872   0.627    0.387
5123.382    0.265   0.573    0.384
5123.478    0.305   0.557    0.371
5124.447    0.709   0.590    0.388
5125.410    0.110   0.609     -
5126.421    0.532   0.525    0.367
5137.433    0.120   0.613    0.378
5139.427    0.951   0.633    0.386
-------------------------------------

                       [FIGURE 1]

curve. The phase of the maximum light would suggest that the
region of the star responsible for optical light variations
(dark or bright spot) did not move on the stellar surface during
the period 1974 (Chugainov's observations) - 1982. It should be
also noted that the B-V colour indicates that the star is redder
at minimum light than during maximum.





                EWA BOHUSZ

                ANDRZEJ UDALSKI

           Warsaw University Observatory
           Al. Ujazdowskie 4
           00-478 Warszawa, Poland





References:
Chugainov P.F., 1976, Izv. Krymskoj Astrof. Obs. 54, 89 [BIBCODE 1976IzKry..54...89C ]
Rucinski S.M., 1981, Astron. and Astrophys. 104, 260 [BIBCODE 1981A&A...104..260R ]