COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1338

                                   Konkoly Observatory
                                   Budapest
                                   1977 September 15




                      VZ CANCRI



      The short-period variable VZ Cnc was observed at Trieste
with a 50-cm Newtonian reflector equipped with a three-channel
UBV simultaneous photometer, at Dr. Todoran's suggestion. We 
report here on the observations made on two nights (Dec. 27, 1976
and Jan. 17, 1977). The results are given in graphical form in
Figs. 2 and 3. We keep the single observations at the disposal
of interested persons.
      Assuming the elements for the principal period and for
the beat period given by Todoran (1976) and the magnitude and
colours of the comparison star HD 73938 (BD +11d1894) given by
Fitch (1955), we derive the elements shown in Table 1, according 
to the corresponding Table 1 of Todoran. The O-Cs fall on
the upper border of the strip shown in his Fig. 1 (O-C vs. psi b,
where psi b is the phase of the beat period) whereas the Vmax are
in perfect agreement with their behaviour, as it is shown in
his Fig. 2 (Vmax vs psi b).
      Our Fig. 1 shows the phase dependent variation of the
colours of VZ Cnc in a (U-B)-(B-V) diagram for the night of
Dec. 27, 1976. The curve is a free-hand drawing through the 
observed values. The numbers referring to the phase show that the
variation is counter-clockwise, a feature common to many RRc
stars. The colours are B-V=+0.23, U-B=+0.11 at maximum light
and B-V=+0.37, U-B=+0.05 or 0.06 just after minimum. They 
correspond to spectral types A7III and F2III (FitzGerald, 1970),in
good agreement with the spectroscopic determinations (Abt, 1955).

                   Table 1
   Max.hel.
   2443000+ Vmax   E      O-C      Eb   psi b

   140.6090 7.46  53311 -0.0021d  13275 0.9612
   161.4850 7.50  53428 +0.0053   13304 0.1057


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


             B. CESTER, G. GIURICIN, F. MARDIROSSIAN
                     M. MEZZETTI, M. PUCILLO
                   Osservatorio Astronomico
                        Trieste, Italy



References:
Abt, H.A. 1955, Astrophys.J. 122, 390 [BIBCODE 1955ApJ...122..390A ]
Fitch, W.S., 1955, Astrophys.J. 121, 690 [BIBCODE 1955ApJ...121..690F ]
FitzGerald, G.P. 1970, Astron.and Astrophys. 4, 234 [BIBCODE 1970A&A.....4..234F ]
Todoran, I., 1976, I.B.V.S. No. 1141