COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1700

                                   Konkoly Observatory
                                   Budapest
                                   1979 November 5


                   BH CENTAURI


   BH Cen is a close (contact) system in the extremely young
cluster Cordoba XXVI (NGC 2944). Oosterhoff (BAN, 4, 183, 1928;
BAN, 5, 156, 1930) obtained photographic observations and derived 
from ten light minima a (half) period P=0.3957907d. Previous
photoelectric observations (Leung and Schneider, Ap.J. 211, 844,
1977) do not cover completely the light curves and indicate that
the period is slightly longer than that found by Oosterhoff.
Since they covered only one minimum they obtained a period by
trial and error based on the consistency of the light curves;
they found P = 0.791616d. Eggen (A.J. 83, 288, 1978) noted that
the light curve of BH Cen is shifted by -0.13p when compared with
Leung and Schneider's elements. We obtained more than 700 UBV 
observations at the Bosque Alegre Station of Cordoba Observatory
and determined five times of minimum light (Table I).

                         Table I

Hel.J.D.      E       (O-C)      E'        (O-C)' Remarks
2400000+

22084.297     -   -           -12209.0    -0.014    1
25025.434     -   -            -8493.5    -0.004    1
25329.408     -   -            -8109.5    +0.002    1
25331.392     -   -            -8107.0    +0.007    1
25351.536*    -   -            -8081.5     -        1
25362.267*    -   -            -8068.0     -        1
25385.228     -   -            -8039.0    +0.016    1
25386.404     -   -            -8037.5    +0.004    1
25404.209     -   -            -8015.5    -0.001    1
25714.497*    -   -            -7623.0     -        1
39621.7975(15) -  -            +9946.0    -0.035    2,3
43987.8119(08)-38.5 -0.0006    +15461.5   +0.0038   4,3
43989.7917(05)-36.0 +0.0002    +15464.0   +0.0046   4,3
43990.5835(04)-35.0 +0.0004    +15465.0   +0.0048   4,3
44028.5796(04)+13.0  0.0000    +15513.0   +0.0049   4,3
44095.4693(05)+97.5  0.0000    +15597.5   +0.0059   4,3

Remarks: 1- Oosterhoff,1928, see text; 2- Leung and Schneider,
1977, see text; 3- p.e. in parenthesis; 4- present observations.

A least squares solution for our minima gives the following
linear ephemeris:

Min.I = Hel.J.D. 2444018.28888 + 0.7915942d * E,  (1)
                      +-.00020  +-.0000038

with the cycles E and residuals (O-C) given in Table I. From
Oosterhoff's photographic minima, excluding the three values
marked with asterisks because their large residuals, we found:

Min.I = Hel.J.D. 2424260.3709 + 0.7915877d * E.  (2)
                      +-.0028  +-.0000017

The periods found from the two sets of observations are slightly
different; the present value is somewhat  longer than that for
the 1920's, however shorter than that suggested by Leung  and
Schneider.
An ephemeris including photographic and photoelectric observations 
gives:

Min.I = Hel.J.D.2431748.7478+ 0.79158298d * E'.  (3)
                     +-.0037 +-.00000031

The residuals (O-C)' of these elements are about +0.0005d  for
our observations, comparable to the p.e., however systematically
shifted; the epoch of minimum light of Leung and Schneider`s
elements yields a residual twenty times larger than the published 
p.e..
The former considerations would indicate that the period
of BH Cen is changing; if Leung and Schneider's minimum is 
correct within the quoted error the residuals of formula (3) may
be caused by a light-time effect with an orbital period of about
50 years and a projected radius R * sin i = 6 x 10^8km. However, to
decide on this point the system must be observed in the future.
The use of ephemeris (1) should be preferred for the prediction
of circumstances in the near future.



                         R.F. SISTERO
                         B.A. CANDELLERO
                         A. GRIECO
                         Observatorio Astronomico
                         Laprida 854, 5000 Cordoba,
                         Argentina