COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1199

                                 Konkoly Observatory
                                 Budapest
                                 1976 November 4




            FOUR COLOUR uvby PHOTOMETRY OF THE
            TOTALLY ECLIPSING BINARY DX AQUARII


      DX Aqr was observed on several nights in 1975 with the
four-channel spectrograph-photometer on the Danish 50 cm reflector, 
Cerro La Silla, ESO, Chile (cf. Gronbech et al. 1976). All
observations have been reduced to standard V magnitudes and
standard four colour indices (b-y, m_1 and c_1). The late-type visual 
companion at 3.7" was included in the diaphragm. Andersen
(private communication) has classified this companion as K0III:
from 20Angstrom/mm coude spectra.
      The primary purpose of the observations was to improve
the ephemeris given by Strohmeier (IBVS 164). One primary minimum 
was followed for five hours and closely covered with 27
points on the descending branch, five points in a total eclipse
phase and 16 points on the ascending branch. The total eclipse
lasts about 20 minutes from HJD = 2442687.690 to 2442687.704.
Combining this minimum with Strohmeier's ephemeris gives an 
improved ephemeris
             HJD(Min.I) = 2442687.697 + 0.9450132d E.
      This new photometric period agrees well with the period
given by Paffhausen and Seggewiss (1976) from spectrographic 
observations and also with the period given in the third supplement
to GCVS (3.ed.).
      The ingress starts at about phase 0.83. In the table the
photometric results inside and outside eclipse are given together
with their mean errors. The strong change in the four colourindices 
during eclipse reflects the dominating influence of the
visual companion. Because of this handicap no further photometry
of this system is planned. The individual observations reported
here are available upon request.

      Outside eclipse     Total eclipse
      Phase 0.71-0.82     Phase 0.993-0.007
      (4 observations)    (5 observations)

V     6.373m +- 0.005m    6.779m +- 0.001m
b-y   0.275  +- 0.003     0.411  +- 0.001
m1    0.145  +- 0.004     0.204  +- 0.002
c1    0.831  +- 0.003     0.659  +- 0.004





                        ERIK HEYN OLSEN

                  Copenhagen University Observatory
                       Brorfelde, Denmark




References:

Gronbech, B., Olsen, E.H. and Stromgren, B. 1976. Astron.
      Astrophys. Suppl. 26, in press [BIBCODE 1976A&AS...26..155G ]
Paffhausen, W. and Seggewiss, W. 1976. Astron.Astrophys.Suppl.
      24, 29 [BIBCODE 1976A&AS...24...29P ]