COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 577

                              Konkoly Observatory
                              Budapest
                              1971 September 6


      A RESEARCH PROGRAM ON SOUTHERN RED DWARFS

      The present observing season is being devoted, at
the I.T.A. Astronomical Observatory, to a survey on some
red dwarfs, in order to make a search for variable stars
which could present the same characteristics as BY Dra,
CC Eri and FF And (1). A preliminary list has been set up
involving almost 30 stars of spectral types dK4 or later
whose apparent magnitudes are below 9.5m in order to be 
observed by a 20-inch telescope. In a first survey these stars
have been studied in the colors B and G of the 6-color
system of Stebbins and Whitford, and only one comparison
star has been taken for each program star. The amount of
stars which had shown some variability was far greater than
expected, and soon check stars became necessary. So, far
some stars whose relative measures show some variability it
has not yet been possible to decide among the red dwarf or
the comparison star. The low rate of elimination has lead
to survey times longer than former previsions. An important
factor in postponing the first stage of this program has
been the bad weather conditions this winter in our region.
      Nevertheless, one of the observed stars has soon
been classified as variable, showing a light-curve close to
that expected for BY Dra stars. It is the star HD 118100 =
BD -7d3646, sp dK5e, V = 9.34m. This star has shown light
changes of 0m10 in both colors. The light variations show
good regularity, the period being close to 4 days (between
4.0 and 4.1 days). In the light curve shown in fig. 1 
magnitudes and color index are referred to the star BD -8d3586,
and zero phases have been calculated by the formula

            JD 2441068,00 + 4.03d E.

The star has been observed 16 times from April 27 to June 1,
and 5 times more at the very end of June. The star
BD -7d3652 has been served as check star.
     For the other program stars almost 50 percent have
been dropped after 5 to 10 photoelectric measures in 
different nights. Besides the star HD 118100 there are at
least 3 more which relative magnitude varied for more than
0.1m. Bad weather conditions. ad impaired the work last
month so we cannot decide which one varied, the comparison
or the program star, except for one case in which light

                      [FIGURE 1]

variability has been shown to be due to the comparison star
(HD 99619 - probably a long period variable; its measures
show sloe variation of about 0.2m in 50 days). Three more
stars have shown variations with smaller magnitude ranges,
but require further observations before some conclusion can
be drawn.    
      The criteria employed to set up the working list 
seem to be good. The list has been revised and could be
published in a future issue of the IBVS.



                 S. FERRAZ MELLO and C.A.O. TORRES
                The I.T.A. Astronomical Observatory
                 Sao Jose dos Campos, SP - Brazil




[References]
(1) P.F. Chugainov, IBVS No. 520 (1971).