COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 731

                                 Konkoly Observatory
                                 Budapest
                                 1972 October 30


  PHOTOELECTRIC OBSERVATIONS OF THE ECLIPSING VARIABLE
                U CORONAE BOREALIS


  Photoelectric observations of U Coronae Boreales in UBV
system were made with the 24-inch reflector at the observing
Station of the Laboratory of Astronomy of the University of
Ioannina (longitude=-1h23m, latitude=+39d37') on eighteen
nights between May and July 1972. The photometer was furnished 
with a 1P21 photomultiplier tube and yellow, blue and 
ultraviolet corning filters 3385, 5562 and 9863.
  The comparison star used was BD + 32d2578, the same one
as previously used by Wood (1958).
  The observations of UCrB in V are plotted in Figure 1,
while the normal points of observations of UCrB in V,B and U
are given in Table 1. The first column of Table 1 gives the
phase in units of the period, while the second, third and
fourth columns give the differences of the magnitude of UCrB
minus that of the comparison star in V, B and U, correspondingly. 
The phases were determined by using the ephemeris of
Dugan and Wright (1939):

    Primary Minimum = J.D. 2416747,964 + 3.45220416 E.

  Using the observations through and near primary minimums
we got the observed times of primary minimum included in 
Table 2. The second column of Table 2 gives the O-C of times of
minima when the computed times of minima were determined by
the Ephemeris of Dugan and Wright, while in the last column of
Table 2 the O-C are determined by using the period given by
S. Catalano, S. Cristaldi and C. Lacona (1966):

              P = 3.4522027d

   Since Wood (1958) found O-C=+0.008 day using Dugan and
Wright's formula given above the present data of Table 2 show
that the period of UCrB continues to become smaller.



                   Table 1
                 Normal Points
--------------------------------------------------
                                      Number of
Phase    DeltaV    DeltaB    DeltaU  Observation
--------------------------------------------------
0,0020   + 0,743   + 0,557   + 0,123   3
0,0085   + 0,673   + 0,339   + 0,006   4
0,0110   + 0,650   + 0,475   - 0,156   3
0,0153   + 0,506   + 0,345   - 0,242   4
0,0173   + 0,478   + 0,297   - 0,182   3
0,0347   + 0,016   - 0,170   - 0,828   3
0,0431   - 0,079   - 0,436   - 0,998   3
0,0529   - 0,214   - 0,501   - 1,110   4
0,0682   - 0,267   - 0,573   - 1,184   6
0,0807   - 0,231   - 0,563   - 1,060   6
0,1262   - 0,194   - 0,565   - 1,027   7
0,2812   - 0,291   - 0,582   - 1,117   6
0,3648     -       - 0,608   - 1,110   -
0,3729   - 0,291   - 0,569   - 1,120   5
0,4113   - 0,249   - 0,565   - 1,029   5
0,4188   - 0,248   - 0,558   - 1,029   5
0,4262   - 0,256   - 0,563   - 1,060   6
0,4598   - 0,227   - 0,568   - 1,085   3
0,4652   - 0,249   - 0,553   - 1,024   3
0,4714   - 0,249   - 0,570   - 1,022   3
0,4777   - 0,217   - 0,544   - 1,084   4
0,5012   - 0,303   - 0,597   - 1,032   4
0,5147   - 0,287   - 0,561   - 1,080   4
0,5901   - 0,260   - 0,559   - 1,050   5
0,5987   - 0,254   - 0,586   - 1,175   5
0,6082   - 0,263   - 0,600   - 1,078   5
0,6957   - 0,285   - 0,641   - 1,097   3
0,7356   - 0,307   - 0,590   - 1,054   5
0,7472   - 0,302   - 0,635   - 1,035   4
0,7497   - 0,286   - 0,673   - 1,089   5
0,7575   - 0,306   - 0,634   - 1,059   4
0,7686   - 0,278   - 0,567   - 1,104   5
0,7894   - 0,270   - 0,584   - 1,143   4
0,8403   - 0,233   - 0,522   - 1,027   6
0,8766   - 0,248   - 0,565   - 1,033   5
0,8867   - 0,229   - 0,541   - 1,058   4
0,8942   - 0,222   - 0,556   - 1,040   4
0,9611   + 0,236   - 0,040   - 0,508   3
0,9666   + 0,358   + 0,110   - 0,312   3
0,9724   + 0,514   + 0,262   - 0,574   3
0,9772   + 0,636   + 0,413   + 0,002   3
0,9834   + 0,765   + 0,574   + 0,151   3
0,9876     -       + 0,631   + 0,089   -
0,9910   + 0,851   + 0,672   + 0,243   4
0,9920   + 0,829   + 0,672   + 0,095   3
0,9974   + 0,828   + 0,655   + 0,175   4
-----------------------------------------------



                 Table 2
--------------------------------------------------
Observed Times of Pr. Minimum  O-C   Weight  O-C
--------------------------------------------------  
2441462.274 +- 0,002         - 0,020   2   - 0,009
    486.436 +- 0,001         - 0,023   3   - 0,013
    493.341 +- 0,001         - 0,022   4   - 0,012
--------------------------------------------------


                      [FIGURE 1]


          S. N. SVOLOPOULOS and S. KAPRANIDIS
              Laboratory of Astronomy
              University of Ioannina
              Greece.



References:

Catalano, S., S. Cristaldi and G. Lacona, 1966, Catania Publ.
   Nuova Serie 84. [BIBCODE 1966MmSAI..37..213C ]
Dugan R.S. and F.W. Wright, 1939, Princeton Contr. 25, 45.
Wood D., 1958, Astrophys.J. 127, 351. [BIBCODE 1958ApJ...127..351W ]