COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                      Number 3138



                                    Konkoly Observatory
                                    Budapest
                                    27 January 1988

                                    HU ISSN 0374-0676



         NEW B,V LIGHT CURVES OF AA URSAE MAJORIS

  AA UMa (S4758) was discovered as an eclipsing variable by Hoffmeister (1948).
A number of periods have been determined. Tsessewitch (1956) gave a period of
3.0703 days and classified it as an Algol system; Meinunger (1961) 0.466352 d as
a W UMa binary; Strohmeier and Ott (1963) 0.763839d as a Beta Lyrae variable;
Meinunger (1976) 0.468106 d and giving UBV light curves but the scatter being
fairly large; and Borovicka (1985) 0.46812555 d. The spectral type of the system
was given to be G2 by Gotz and Wenzel (1961); F8 by McDonald (1964); G0 listed
in GCVS; and G0 by Lu (1988). The system was observed with the 60-cm reflector
at Xinglong station of Beijing Astronomical Observatory on 7 nights in 1987,
Its light curves were both in B and V well covered in phase. Six minima secured
are as follows :

          (JD hel 2,440,000+)
          6,857.2571(II) 6,885.1121 (I)
          6,859.1304(II) 6,886.0493 (I)
          6,860.0650(II) 7,118.2393 (I)

  The stars BD +46 1544 and +46 1545 were employed as the comparison and
check stars, respectively, In order to determine the magnitudes and colours
of the variable, comparison and check, the star HD 84035 (BD+43 1953) was used,
The standard deviation in a single check-comparison magnitude was 0.007 in B
and V, which indicated that the comparison was satisfactorily constant, The
new observations showed that the depths of the primary and the secondary
eclipses were almost identical in B, but in V the depth at phase zero was
definitely deeper than that at phase 0.5.
  Combining 39 moments of minima found in the literature, the new light 
elements of the system derived is :

          Hel. Min.I= 2,446,885.1119+0.46812583d E
                              +/- 21      +/-21


                               [FIGURE 1]

                  Figure 1: Light curves of AA UMa


   By comparing our minima with those determined by Meinunger, a correction
of half a cycle was made to Meinunger's. This would imply that the light curves
of AA UMa were variable like in the case of TZ Boo. A plot of differential 
magnitudes of the system with the new elements is shown in Figure 1. It is noted
that the B-V index determined here is 0.60m at maxima instead of 0.64m given by
Meinunger. The former is in very good agreement with G0 from the spectroscopic
classification by Lu. It is also noted that O'Connell effect in AA UMa is 
obvious. A united photometric and spectroscopic analysis of the system is under
way and will be given elsewhere.


                          LU WENXIAN
                          WANG RUYOU
                          FAN QINGYUAN

                       Shanghai Observatory
                         Academia Sinica
                         Shanghai, China

References:
Borovicka, J., 1985, Brno. Obs. and Plan. Contr. No. 26, 48, [BIBCODE 1985CoBrn..26...45B ]
Gotz, W. and Wenzel, W., 1961, MVS, 1, 570.
Hoffmeister, C., 1948, Erg. A.N. 12, 1.
Lu, W.X., 1988, Acta Astrophysica Sinica, 8. [BIBCODE 1988AcApS...8...26L ]
Mc Donald, D., 1964, Virginia Publ. XII, 54
Meinunger, L., 1961, MVS, 1, 557.
Meinunger, L., 1976, MVS, 7, 139.
Strohmeier, W. and Ott, H., 1963, IBVS, No. 38.
Tsessewitch, V.P., 1956, AC Kasan, No. 170.