COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1857

                                   Konkoly Observatory
                                   Budapest
                                   1980 October 20

                                   HU ISSN 0374-0676


         THE PERIOD OF V154 IN NGC 5272 (M3)



   The variability of the star was discovered visually by
Barnard (1906). Greenstein (1935), Arp (1955) and Kholopov (1972)
published photographic observations of the star. A radial velocity
curve was published by Joy (1940). These authors concluded that
V 154 is a W Vir star, changing its light between 12.1m - 13.7m in
B and 12.0 - 13.25m in V. The spectral type varies between F5
and G3.
   Between spring 1976 and spring 1979 we took 25 Kodak 103a-D
plates of NGC 5272 with the 314/5000 mm two lens refractor of
the Wilhelm Foerster Observatory, Berlin. The plates were exposured 
10 to 30 minutes behind a Schott GG495 filter. As the variable 
is located near the center of the cluster, it was not possible 
to measure the star with an iris photometer. Therefore,the
star was estimated by the Argelander step method using seven
comparison stars. The resulting magnitudes have an accuracy of
about 0.05m.
   With the period value P=15.2854d we reduce the observations
to one period and determined from the resulting light curve an
actual time of maximum by the Pogson method. This value is listed
in Table I together with the values derived by the above cited
authors. The epochs and O-C values were calculated with Arp's
elements
         Max.= 2424627.55d + 15.2854d.E     (1)
and are shown in the Figure. Formula (1) represents the values
of Greenstein, Arp and Kholopov. Our new observations indicate
a period change because the O-C is significantly greater than the
error of our maximum timing. If one makes a linear fit between
the value of Kholopov, one can derive a first approach to the
new period value. We find an actual value of P_a=15.2842d which
means that the period has shortened by approximately 1m45s. The
value DeltaP/P is -7.8*10^{-5}. Another period change is indicated by

the large O-C value of Barnard's observations.
                    Table I
  Observed times of maxima of V 154 in NGC 5272
Maximum (J.D.)        E     O-C    Reference
24 16604.6d         -525   +1.89d   Barnard (1905)
   24627.55           0     0.00    Greenstein (1935)
   34119.8 +-0.15d  +621   +0.02    Arp (1955)
   34150.4           623   +0.05    "
   34180.9           625   -0.02    "
   38873.53          932   -0.01    Kholopov (1972)
   42862.71+-0.08   1193   -0.32    this paper.


                       [FIGURE 1]

  U. HOPP

Wilhelm Foerster Observatory
Berlin, F.R.G.


References:
Arp, H., 1955: Astron. J. 60, 8 [BIBCODE 1955AJ.....60....1A ]
Barnard, E.E., 1905: Astron.Nachrichten 172, 345 [BIBCODE 1906AN....172..345B ]
Greenstein, J.L., 1935: Harvard Bull. 901, 16
Joy, A.H., 1940: Astrophys. J. 92, 396 [BIBCODE 1940ApJ....92..396J ]
Kholopov, P.N., 1972: Astron. Cirk. 676, 7 [BIBCODE 1972ATsir.676....7K ]