COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 1055

                                  Konkoly Observatory
                                  Budapest
                                  1975 October 27




           PHOTOELECTRIC PHOTOMETRY OF CW Ser



The RR_s-star CW Ser was observed photoelectrically in two successive 
nights in June, 1975. It was observed because no photoelectric 
data of this star have been published so far. The third edition 
of the GCVS (Kukarkin et al., 1970) gives a photographic magnitude 
variation between 11m and 12m.
Our differential measurements in B and V are listed in Table 1.
Comparison star was a 10th magnitude star 2' south and 39^s east
of CW Ser. Each value in Table 1 is a normal point corresponding
to a total integration time of 160 sec.
The light curves are shown in Fig. 1. The measurements of June 11
have been plotted as circles, those of June 12 as crosses.  The
larger scatter of the observations of June 12 is caused by minor
weather conditions. Two times of maximum have been determined.
They are
             Max. = JD_Hel 2442575.500
                                   +-1
         and Max. = JD_Hel 2442576.443
                                   +-1
According to these values and the epoch given in the GCVS the period 
has to be slightly increased by 4 units on the eighth digit.
The improved period value is
              P = 0.18915054d
                         +-1
The amplitudes in B and V are
              DeltaB = 0.75m +- 0.05m
              DeltaV = 0.50m +- 0.05m
The time for the rising branch is 0.32 periods,confirming the value
given in the GCVS. The photographic amplitude, however, is smaller
than the value given in the GCVS.
Comparison of the observations of the two different nights suggests 
that an amplitude variation may occur in CW Ser, as it is observed
for many other RR_s-stars.

                        Table 1
JD_Hel2442000+    DeltaB    JD_Hel2442000+    DeltaV
 575.4299         1.00       575.4350         1.50
    .4368         0.94          .4369         1.46
    .4455          .89          .4442         1.47
    .4526          .79          .4492         1.42
    .4593          .71          .4556         1.36
    .4659          .64          .4613         1.27
    .4716          .56          .4677         1.25
    .4780          .43          .4752         1.05
    .4855          .34          .4823         1.06
    .4906          .28          .4884         1.05
    .4958          .19          .4936         1.02
    .5013          .21          .4988         0.97
    .5072          .23          .5047         0.98
    .5135          .26          .5107         0.98
    .5190          .38          .5165         1.06
    .5250          .42          .5219         1.11
    .5310          .43          .5286         1.12
    .5363          .46       576.4096         1.31
 576.4104          .66          .4156         1.25
    .4169          .54          .4188         1.18
    .4238          .39          .4274         1.07
    .4353          .22          .4360         0.99
    .4410          .24          .4408         1.00
    .4476          .23          .4471         0.97
    .4599          .34          .4589         1.03
    .4648          .37          .4641         1.06
    .4691          .38          .4686         1.06
    .4764          .41          .4759         1.05
    .5106          .62          .4811         1.07
    .5160          .68          .4889         1.06
    .5224          .69          .4939         1.12
    .5325          .67          .4997         1.16
    .5413          .69          .5077         1.17
    .5486          .77          .5134         1.22
    .5564          .78          .5182         1.26
    .5610         0.90          .5254         1.29
                                .5349         1.33
                                .5439         1.31
                                .5514         1.33
                                .5585         1.34
                                .5616         1.36



Observatorium Hoher List      
der Universitats-Sternwarte Bonn
5568 Daun/Eifel, F.R.G.
      

                           W. GIEREN
                           F. GIESEKING
                           M. HOFFMANN


                      [FIGURE 1]