COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 3006



                                        Konkoly Observatory
                                        Budapest
                                        3 April 1987

                                        HU ISSN 0374-0676


        UNEXPECTEDLY EARLY FADING OF V644 CEN (CPD -60d 3278)

   This star was discovered to be variable by O'Connell (1951) who observed
the star fade by 0.65 magnitudes on plates taken between 1931 and 1950.
O'Connell proposed that V644 Cen was an eclipsing variable having a period
of at least 65 years and a minimum lasting 17 to 18 years. Gaposchkin (1951)
examined Harvard patrol plates covering the period 1890 to 1949 and concluded
that whilst the star underwent minor disturbances of approximately 0.2 magnitudes
between 1901 and 1920, there was no evidence for a deep minimum until
the one reported by O'Connell. Sahade (1952) noted that the star had a shell
spectrum at the time of the 1951 minimum. Hopp and Kiehl (1977) reported 
analysis of Bamberg sky survey plates which showed that during the period
1964-1975 the star had returned to a new maximum light of approximately
8.86 mpg.

  We observed this star in the Johnson UBV bands on 18 occasions between
JD 2444742 and JD 2445809 during a shell star monitoring programme (Kilkenny
et al. 1985) Our results (Table I and Figure 1) show that during this period

                Table I: 

    MJD              V     B-V          U-B
    4742.327        9.911  0.083       -0.632
    4979.571       10.025  0.081       -0.585
    4979.573       10.021  0.082       -0.587
    4980.560       10.018  0.083       -0.591
    4980.565       10.031  0.075       -0.592
    5075.368       10.148  0.089       -0.433
    5101.406       10.100  0.096       -0.526
    5102.304       10.106  0.094       -0.528
    5106.284       10.096  0.096       -0.524
    5140.236       10.123  0.087       -0.496
    5419.429       10.235  0.077       -0.339
    5419.473       10.257  0.048       -0.342
    5420.490       10.228  0.077       -0.358
    5424.389       10.235  0.073       -0.355
    5427.419       10.262  0.072       -0.343
    5710.592       10.294  0.054       -0.405
    5715.592       10.327  0.046       -0.372
    5809.459       10.213  0.069       -0.365
    

                               [FIGURE 1]


the star was fading steadily and towards the end of our programme had reached
a V magnitude of approximately 10.3 (equivalent to mpg of 10.2) which is
close to the value reported by O'Connell (1951) and Gaposchkin (1951) for the
1950 minimum. We obtained a single point which may indicate that the star was
beginning to brighten again on JD 2445809, but this may be related to small
fluctuations superimposed on the minimum such as was seen in the data of
O'Connell (1951).
   These results clearly show that the lightcurve is more complex than that
of a simple eclipsing variable for which, on the evidence of the Harvard plates,
no deep minimum would be expected until at least the year 2010.
   The current minimum may last until the end of the decade and further
observations of the star, both photometric and spectroscopic, would be 
valuable.


               J K DAVIES, Royal Observatory, Edinburgh, Scotland
               A EVANS, Keele University, Staffordshire, England
               M P BODE and D C B WHITTET, Lancashire Polytechnic.
                               Preston, England

References:
Gaposchkin, S. 1951, Publ. Astron. Soc. Pac. 63. 80. [BIBCODE 1951PASP...63...80G ]
Hopp, U, and Kiehl, M. 1977, Inf.Bull.Variable. Stars No. 1330
Kilkenny, D., Whittet, D.C.B, Davies, J.K., Evans, A., Bode, M.F., Robson, E.I.
     and Banfield, R.M., 1985 S.Afr. Astron. Obs. Circ. 9. 55. [BIBCODE 1985SAAOC...9...55K ]
O'Connell, D.J.K., 1951, Mon. Not. RAS 111. 111 [BIBCODE 1951MNRAS.111..111O ]
Sahade, J. 1952, Astrophys. J. 115. 578 [BIBCODE 1952ApJ...115..578S ]