COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1936

                                  Konkoly Observatory
                                  Budapest
                                  1981 March 11

                                  HU ISSN 0374-0676



                A PHOTOMETRY OF AZ Vir


    The variability of AZ Vir has been discovered by Jensch
(1937). Although several authors observed about a dozen 
minima times, as late as 1974 Busch found the correct period
of 0.35d for this W UMa type eclipsing binary. A photoelectric
light curve has been published by Meinunger (1977).
    Photoelectric measurements of AZ Vir have been obtained
in April 1976, May 1978, and April 1979. They have been
carried out with the double beam photometer at the 1.06m 
reflector of Hoher List Observatory. The mainly used comparison
star "b" is the same as that of Meinunger. Check stars "a"
and "c" are 14s west/ 8' south and 58s east/ 4' south of
AZ Vir, respectively, all stars being of the same order of
magnitude.
    Minima times have been determined:
        JD hel.2442885.413     Ep. 42781.0   O-C +0.003d  
      	       2442885.591         42781.5       +0.006d
               2442886.448         42784.0       -0.011d
               2443656.424         44986.0       +0.003d
               2443976.536         45901.5       -0.003d
Epochs and O-C's are according to the ephemeris
    Min. I = JD 2427926.4052 + 0.3496646871d E
No larger period changes seem to be present during the last

                         [FIGURE 1]

            Fig. 1   B observations of AZ Vir


                         [FIGURE 2]

            Fig. 2   V observations of AZ Vir


three decades.
    Figs. 1 and 2 show the B and V measurements relative
to star "b". Generally the light curves confirm the observations 
published by Meinunger (those phases should be shifted
by 0.5p to place the deeper minimum at phase 0.0). Between
1976 and 1978 no changes in the light curve were detected.
The 1979 measurements fill the gap between phases 0.65 and
0.85. Although the minima show some asymmetry and there are
other indications of minor complications, an analysis of the
orbital elements has been tried by means of the Russell-
Merrill method and using the atlas of theoretical light
curves for contact binaries by Anderson and Shu (1979). The
former showed that the primary minimum is probably a transit
(partial eclipses), but the rectified eclipses are moderately
shallow, and no solution could be obtained. The latter method
yields a best representation of the light curve with
       q = 0.65 +- 0.10       f = 0.8
       i =  70d +-   5d    beta > 0
and full limb darkening.
    With k = q^0.55, a good empirical relation for W UMa
systems with periods shorter than 0.5d, a ratio of the radii
k=0.8 is obtained.
    A part of the work has been supported by the Deutsche
Forschungsgemeinschaft (Schm 167/12). This shall be herewith
acknowledged.



	                       M. HOFFMANN
        	           Observatorium Hoher List
                   	    5568 Daun / Eifel, BRD


References:
Anderson, L., and Shu, F. H., 1979, Astrophys. J. Suppl. Ser.
          40, 667 [BIBCODE 1979ApJS...40..667A ]
Busch, H., 1974, Mitt. Hartha Heft 7, 6
Jensch, A., 1937, Beob. Zirk. 19, 10
Meinunger, L., 1977, Mitt. Veranderliche Sterne Sonneberg 7,
          Heft 8, 185 [BIBCODE 1977MitVS...7..185M ]