COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 659

                                      Konkoly Observatory
                                      Budapest
                                      1972 April 12


                        W UMa 
        PHOTOELECTRIC MINIMA AND A NEW PERIOD VARIATION


The period of W UMa was retained constant since 1951 and the light elements
were:

Min I=J.D. 2435918.4154+0.33363808 E.

The figure shows the residuals referred to these elements, starting only from
1961. Between the end of 1963 and 1964, a delay of about 7 minutes occurred in
the epochs of minimum without change of period: the observations till 1969
were well represented by only adding a constant term of +0.00525 to the zero
epoch. A trend to a slightly shorter period was suspected after the
observations of 1969 (Cester 1969, 1971) but the correction to the period
amounted to only -7.10^-8. The observations of 1971 and 1972 confirm the
suspicion and now the period is decidedly shorter. The new provisional
elements deduced from the observations from 1970 to 1972 should be

Min I=J.D.2440652.4107+0.3336369 E.

i.e. the period variation begun after 1968-69 is of the order of 10^-6 days.

The unpublished recent photoelectric minima obtained at Trieste are collected
in the table: (O-C)_1 refers to the first light elements and (O-C)_2 to the
latter ones.

Hel. J.D.
2441000+      m.e.         (O-C)_1     (O-C)_2
004.3979   +-0.0003        +0.0036     +0.0003
008.40114    0.00006       +0.0032     -0.0001
048.4376     0.0014        +0.0032     -0.0001
057.44612    0.00005       +0.0034     +0.0002
061.4492     0.0002        +0.0028     -0.0003
061.4491     0.0001        +0.0027     -0.0004
351.3799     0.0008        +0.0020     -0.0001
363.3910     0.0001        +0.0021     +0.0001
392.4175     0.0010        +0.0021     +0.0002
396.421313   0.00004       +0.0023     +0.0003

Ref.:

B. Cester, 1969 Mem SAIt 40, 489 [BIBCODE 1969MmSAI..40..489C ]
B. Cester, 1971 Mem SAIt 42, 61. [BIBCODE 1971MmSAI..42...61C ]

                         [FIGURE 1]


B. CESTER and M. PUCILLO
Osservatorio Astronomico
Trieste, Italy