COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        NUMBER 757

                                       Konkoly Observatory
                                       Budapest
                                       1973 January 18


    PHOTOELECTRIC OBSERVATIONS OF 31 CYGNI IN THE 1972 ECLIPSE



   On thirty-two nights between April and August of 1972, UBV
photoelectric observations of 31 Cyg were carried out by Sato
and Hayasaka at the Akita University with the 25 cm reflector
(UBV), by Ogata at the Kanagawa Education Centre with the 20 cm
refractor (BV), and by Kitamura at the Okayama Astrophysical 
Observatory with the 91 cm reflector (UBV). These cooperative 
observations were made to collaborate with the international 
campaign on 31 Cyg in the 1972 eclipse which was decided by the
Commission 42 of IAU with Dr. K.O. Wright as coordinator.
  The observations of 31 Cyg were made differentially with
respect to 26 Cyg as the comparison star, and standard stars of
Johnson were also observed on each night to make it possible to
reduce the individual observations to the standard UBV system.
Description of the photoelectric equipment used was already made
elsewhere (e.g. Tokyo Astr.Bull.Sec.Series No. 221, 1972).



                           Table 1
            UBV Photoelectric Observations of 31 Cyg.
----------------------------------------------------------------------
Date (UT)  JD (Hel)   DeltaU       DeltaB  DeltaV  Observatory*
1972
----------------------------------------------------------------------
Apr.10 2441418.1938   -1.676m      -1.096m -1.258m   A
              .2034   -1.704       -1.093  -1.255    A
       12  420.2786       -        -1.104  -1.282    K
       14  422.3042       -        -1.075  -1.284    K
       17  425.2633       -        -1.113  -1.274    K
       27  435.2776       -        -1.091  -1.269    K
       29  437.2579       -        -1.105  -1.269    K
May     1  439.2726       -        -0.821  -1.207    K
        2  440.2477       -        -0.742  -1.183    K
        6  444.2461       -        -0.719  -1.196    K
        7  445.1465   -0.037       -0.698  -1.184    A
              .1504   -0.002       -0.662  -1.156    A
        9  447.1881   -0.047       -0.693  -1.165    A
              .1964   -0.072       -0.702  -1.162    A
       10  448.1287   -0.017       -0.668  -1.148    A
              .1370   -0.024       -0.678  -1.139    A
       11  449.2719      -         -0.712  -1.178    K
       14  462.2524      -         -0.690  -1.169    K
       18  466.2040      -         -0.696  -1.174    K
       31  469.1411   -0.018       -0.676  -1.158    A
              .1494   -0.026       -0.683  -1.143    A
Jun.    1  470.1913   -            -0.715  -1.189    K
        2  471.0974   -0.035       -0.692  -1.735    A
              .1058   -0.019       -0.681  -1.152    A
        5  474.0697   -0.020       -0.678  -1.162    A
        6  475.0961   +0.002       -0.678  -1.168    A
              .1045   +0.003       -0.679  -1.192    A
              .1887      -         -0.708  -1.184    K
Jun.10 2441479.1026   -0.016       -0.682  -1.156    A
              .1109   -0.016       -0.679  -1.162    A
              .1186   -0.034       -0.687  -1.171    A
              .1739     -          -0.715  -1.201    K
18         487.1173     -          -0.708  -1.203    K
23         492.0731   -0.012       -0.689  -1.176    A
              .0802   -0.036       -0.675  -1.167    A
25         494.0567   -0.042       -0.691  -1.152    A
              .0646   -0.022       -0.694  -1.158    A
26         497.0899     -          -0.710  -1.196    K
27         498.0945     -          -0.697  -1.192    K
28         499.0741     -          -0.715  -1.172    K
Jul. 1     500.0917   -0.054       -0.738  -1.173    O
              .0955     -          -0.777  -1.207    K
              .1140   -0.064       -0.743  -1.179    O
              .1244   -0.084       -0.762  -1.198    O
              .1313   -0.086       -0.767  -1.204    O
              .1397   -0.096       -0.759  -1.201    O
              .1473   -0.085       -0.766  -1.196    O
              .1931   -0.098       -0.775  -1.203    O
3          502.0716   -1.162       -0.974  -1.258    A
              .0819   -1.238       -0.997  -1.243    A
7          506.0789     -          -1.047  -1.269    K
20         519.0325     -          -1.083  -1.271    K
Aug. 4     533.9956     -          -1.055  -1.284    K
-----------------------------------------------------------

*Observatories: A=Akita, K=Kanagawa, O=Okayama.



                    Table 2.
          Depths of the Minimum in UBV.
                    DeltaU       DeltaB       DeltaV
------------------------------------------------------
Outside eclipse   -1.690m(2)   -1.088m(7)   -1.273m(7)
                    +-9(p.e.)    +-5          +-3
Within totality   -0.025(20)   -0.690(28)   -1.168(28)
                    +-3          +-2          +-2
Depth              1.665        0.398        0.105
------------------------------------------------------
Numbers in () give the number of observations used.


   All the results expressed in the magnitude-differences
m_31 Cyg -m_26 Cyg in the UBV system are given in Table 1, where
the notations have usual meanings and each Kanagawa value of
DeltaB, DeltaV is the mean of several observations. The resultant 
observations are also plotted in the figure. A systematic 
difference of the order of 0.02 ~0.03m in B and V remains between
the Akita and Kanagawa observations. From the average values
of DeltaU, DeltaB, DeltaV outside eclipse and within totality, the 
corresponding depths on the light curve are deduced as shown in
Table 2. From our light curve, the epoch of mid-eclipse can be
estimated to be JD 2441469.5 and the duration of totality to be
about 57 days.
    We are thankful to Dr. K.O. Wright (Dominion Observatory) and
Dr. K. Gyldenkerne (Copenhagen Observatory) for their useful 
information on this campaign.


                   [FIGURE 1]



                  T. HAYASAKA and N. SATO,
                  Akita University,
                  H. OGATA, Education Centre
                  of Kanagawa Prefecture,
                  M. KITAMURA, Tokyo Astronomical
                  Observatory, Japan.