COMMISSIONS 27 AND 42 OF THE IAU
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 4003


                                             Konkoly Observatory
                                             Budapest
                                             16 March 1994

                                             HU ISSN 0374 - 0676


        II-52 - A NEW SHORT PERIOD VARIABLE STAR IN M3


  II-52 (Sandage, 1953) is located at the lower part of the red giant branch (see Figure
1). Its brightness is fainter than that of the horizontal branch by about one magnitude.
The magnitude and colors of the star are V=16.77, B-V=0.65, U-B=-0.01 (Johnson
and Sandage, 1956). The coordinates of the star relative to the cluster 
center are: x=65",
y=257". Unfortunately, neither radial velocity nor proper motion determinations are
found in literature. To assign the membership of a star according to its position in the
C-M diagram (photometric criteria) generally agrees with the proper motion determinations 
in M3, however, the photometric criteria assigned a few field stars to the cluster
and vice versa (Cudworth, 1979).
  Surprisingly, II-52 appears to be a new short period variable star. The CCD data we
used and the procedure for analysing the variation are the same as those used before (Yao
et al.,1993a, 1993b). The same star AO was used as the comparison star. A 
frequency of
v=approx.3.92 with a height of Z=20.36 in the periodogram was searched out, i.e., the false alarm
probability F must be very low and the variation of the star is real. However, due to the
fact that II-52 is fainter than AO by about two magnitudes, the photometric precision is
not as high as that for vZ1140 and vZ1055 (Yao et al.,1993a, 1993b). The folded light
curve is shown in Figure 2 which can be represented by the following formula:

             Delta m(t)=2.10 + 0.01716 sin(2pi t/P + 2pi phi)


                         [FIGURE 1]
                         [FIGURE 2]
                         [FIGURE 3]

 Here the 2.10 is the mean magnitude difference between II-52 and AO, P=0.25510 day,
phi=0.7670. The "real time" light curves are shown in Figures 3, 4, 5, 6. The symbols in
the figures are the same as before (Yao et al., 1993a).
 We also used another comparison star (II-58) to check the result, a slightly different
period P=0.25306 day was found. The similar folded light curve is shown in Figure 7.
Though the magnitude and color of II-58 (V=16.66, B-V=0.67) are similar to that of
II-52, the scatter in Figure 7 is larger than that in Figure 2 due to the faintness of both
II-52 and II-58.
 As far as we know, this is the first report on the variation of a star located at such
a position in the C-M diagram (if II-52 is really a cluster member). We hope that the
result will be checked by other observers independently.
 This work was supported in part by the grant from the Chinese National Science
Foundation.

                         [FIGURE 4]
                         [FIGURE 5]
                         [FIGURE 6]
                         [FIGURE 7]


                         YAO BAO-AN
                         ULOA/CAS
                         Shanghai Observatory
                         China

                         ZHANG CHUN-SHENG
                         QIN DAO
                         Purple Mountain Observatory
                         China



References:

Cudworth, K. M., 1979, A. J., 84, 1312 [BIBCODE 1979AJ.....84.1312C ]
Johnson, H. L., and Sandage, A. R., 1956, Ap. J., 124, 379 [BIBCODE 1956ApJ...124..379J ]
Sandage, A. R., 1953, A. J., 58, 61 [BIBCODE 1953AJ.....58...61S ]
Yao, Bao-an, et al., 1993a, IBVS, No. 3955
Yao, Bao-an, et al., 1993b, IBVS, No. 3962