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

                   Number 446

                             Konkoly Observatory
                             Budapest
                             1970 July 8



     PHOTOELECTRIC TIME OF MINIMUM FOR AI CRUCIS


The eclipsing binary AI Cru was observed photoelectrically
on the UBV system on one night in March 1970 at the No. 1
16-inch telescope of the Cerro Tololo Inter-American Observatory. 
A finding chart is given by Wesselink /1969/
wherein AI Cru is Wesselink's star No. 1 and the comparison
star used by me is Wesselink's star No. 2
                             




                                Table A


        HJD             Delta V         Delta /B-V/     Delta/U-B/
2440676.7489            +0.125          -0.016          -0.077
       .7510              .161          -0.020          -0.079
       .7554              .156          -0.008          -0.078
       .7575              .202          -0.032          -0.095
       .7618              .201          -0.015          -0.086


       .7641            +0.214          -0.018          -0.084
       .7696              .258          -0.019          -0.062
       .7718              .268          -0.005          -0.078
       .7764              .317          -0.033          -0.063
       .7786              .311          -0.032          -0.050

       .7836            +0.353          -0.039          -0.044
       .7858              .358          -0.022          -0.062
       .7900              .377          -0.020          -0.044
       .7923              .398          -0.031          -0.047
       .7971              .440          -0.028          -0.046

       .7991            +0.438          -0.018          -0.050
       .8033              .435          +0.005          -0.059
       .8055              .457          -0.007          -0.053  
       .8114              .450          +0.001          -0.030
       .8135              .434          +0.025          -0.061

       .8184            +0.464          -0.022          -0.045
       .8208              .452          -0.014          -0.043
       .8403              .356          +0.022          -0.084
       .8428              .353           0.000          -0.062
       .8479              .318          -0.019          -0.051

       .8503            +0.312          -0.012          -0.070
       .8570              .254          +0.001          -0.072
       .8591              .250          -0.020          -0.085
       .8819              .091          +0.013          -0.091
       .8840              .096          -0.001          -0.084

       .8879            +0.076          -0.022          -0.058
       .8900              .054          -0.006          -0.068


                   
Column 1 in Table A lists the heliocentric Julian Date.
Columns 2, 3 and 4 list the differential V, /B-V/ and
/U-B/ magnitude and color indices in the sense variable
minus comparison. The times of observation are accurate to a
few seconds. The accuracy of the photometry is within
+- 0.02 magnitudes

The derived heliocentric Julian Day time of primary minimum
is HJD 2440676.813 +- 0.001 as derived by the technique
outlined by Kwee and van Woerden /1956/. When compared to
the ephemeris quoted by Koch, Sobieski and Wood /1963/, the
O-C for this primary minimum is +0d018.

This work was supported by the National Science Foundation.





                ARLO U. LANDOLT
                Louisiana State University Observatory
                Baton Rouge, Louisiana


References

Koch, R.H., Sobieski, S., and, Wood, F.B, 1963. Publ. of
      Univ. of Pennsylvania, Astronomical Series Vol.9.
Kwee, K.K., and van Woerden, H.1956, Bull. Astron.Inst.
      Neth. 12, 327 /No.464/. [BIBCODE 1956BAN....12..327K ]
Wesselink, A.J. 1969 M.N.R.A.S. 146, 329. [BIBCODE 1969MNRAS.146..329W ]