COMMISSION 27 OF THE I.A.U.
               INFORMATION BULLETIN ON VARIABLE STARS
                            Number 1465

                                                      Konkoly Observatory
                                                      Budapest
                                                      1978 August 28


           S4831, A PROBABLE RV TAURI TYPE

Using the data taken from the Maria Mitchell Observatory
plate collection on Nantucket Island, Massachusetts, the light
curve of the suspected variable star in Cygnus, S4831, clearly
exhibits characteristics of the RV Tauri class of intrinsic
variables. The light curve of S4831 shows alternating shallow
and deep minima, including several irregularities. Occasionally,
two deep minima occur in succession, the duration of each being
roughly half the period of the periodic portions of the light
curve.


   Irregular cycles
Julian Dates   Duration

26875-26995    120 dy
28345-28490    145 dy
29390-29550    160 dy

The star was visible on photographic plates as far back
as 1916, but the best data sequences, producing nearly complete
light curve, occurred within the period from July 1930 to 
December 1940, (JD 26000-30000). There seems to be a series of 
irregular variations from May 1968 to May 1971 (JD 40000-41000)
in which there are intervals of as much as 200 days when the
star did not vary at all. However, it is these irregularities
which identify S4831 as an RV Tauri type star rather than some
periodic star, say Beta Lyrae, or a long period variable as
portions of its curve would indicate.
   The magnitude of S4831 varies from a minimum of +15.0 to
a maximum of 13.2, (Delta m=1.8). The average (~+14.3) varies with
each cycle, due to the varying depths of the minima, (Figure 2).
Since RV Tauri stars are usually G to K spectral class 
supergiants, it would be desirable to have some spectra on this star.
As a matter of interest, a very rough approximation  of
the distance would put S4831 at 25 kpc. This is the maximum
distance it could be, because the effects of galactic 
absorption were not taken into consideration. (The average magnitude 
of +14.3 was used for apparent magnitude and -3.4 was used
as an approximation for this type of star's absolute magnitude.)


                         KAREN MEECH

                         Maria Mitchell Observatory
                         Nantucket, Mass. 02554, U.S.A.


The investigation of the suspected variable S4831 was carried
out with the support of a scholarship from EARTHWATCH of Belmont,
Massachusetts.


                        [FIGURE 1]

   Magnitude of                        Bonner
  Comparison stars                  Durchmusterung
                                    Catalog Number
   a 11.7                            A 3468
   b 13.1                            B 3467
   c 13.6
   d 14.8
   e 15.8


                        [FIGURE 2]

                    Variation of Minima
 Ordinate axis - marked at tenths of magnitudes. Graph covers
 interval from JD 26000 to JD 30000; marked at each 1000 days.


                         [FIGURE 3]

 Ordinate axis - magnitude markers begin at 13, with one magnitude 
intervals to 15th magnitude. Each strip represents 1000 days, 
markers placed at 100-day intervals:

           Part 1            Part 2          Part 3
    A 26000-27000          G 33000-34000   M 39000-40000
    B 27000-28000          H 34000-35000   N 40000-41000
    C 28000-29000          I 35000-36000   O 41000-42000
    D 29000-30000          J 26000-37000   P 42000-43000
    E 30000-31000          K 37000-38000   Q 43000-44000
    F 32000-33000          L 38000-39000