COMMISSION 27 OF THE I.A.U.
               INFORMATION BULLETIN ON VARIABLE STARS
                            Number 1462

                                                      Konkoly Observatory
                                                      Budapest
                                                      1978 August 22


           IMPROVED EPHEMERIS FOR HD128141

The G-type star HD128141 was discovered to be a binary star
of W UMa type by Bond (1975), who gave the preliminary ephemeris

               JD_hel = 2442537.433+ 0d.355 * E.

We observed this star on 24 nights between April 1976 and June
1978 to obtain its light curve and improved ephemeris. The 
observations were made in two colours using an EMI6256S photomultiplier 
tube and standard B,V filters attached to the 30 cm Maksutov
telescope of the University Observatory at Ankara. The comparison
star was HD 128128,and HD 128186 and BD +9d2919 were used as occasional 
checks.

  The observed times of minima are given below:


    MJDhel     m.e.        E         O-C

2442536.933 *           -1013.5    +0.0017
  42896.8763+-0.0004 V      0      +0.0004
       .8746       7 B             -0.0013
  42897.9419       6 V      3      +0.0005
       .9418       5 B             +0.0004
  43225.0333       5 V    924      -0.0013
       .0334       4 B             -0.0012
  43228.9410       5 V    935      -0.0002
       .9408       3 B             -0.0004
  43230.0068       3 V    938      +0.0001
       .0072       9 B             +0.0005
  43340.8120       8 V   1250      -0.0015
       .8130      16 B             -0.0005
  43573.0842       8 V   1904      +0.0025
       .0850       8 B             +0.0033
  43666.8402      10 V   2168      -0.0011
       .8399      10 B             -0.0014
  43669.8616      10 V   2176.5    +0.0015
       .8600      13 B             -0.0001

*Bond (1975)

The first entry was taken from Bond. The times of minima
and the associated errors were calculated by the method of Kwee
and van Woerden (1956).
   According to the present observations, the epoch given by
Bond corresponds to the minimum that is approximately 0m.02 less
deep. We have therefore considered it to be the epoch of the 
secondary minimum.
   The following ephemeris was obtained from the table:

        MJDhel (Min I) = 42896.8759 + 0d.3551501 * E.
                               +- 3         +- 3

   After an initial graphical solution, the O-C value for each night
(V and B combined) was assigned weight according to the mean
error given above. For the first entry +-0.001 was adopted. Exclusion 
of the night with E=1904, with a large O-C, did not change
the result significantly. The secondary minima were included in
the solution with the assumption that the phase difference is
exactly half the period.


                          Z. ASLAN

                  Ankara University Observatory
                A.U. Fen Fakultesi, Ankara-Turkey



References:

Bond, H.E., 1975, P.A.S.P. 87, 877 [BIBCODE 1975PASP...87..877B ]
Kwee, K.K. and van Woerden, H., 1956, Bull. Astron. Neth. 12, 327 [BIBCODE 1956BAN....12..327K ]