COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3674   
 
                                                 Konkoly Observatory
                                                 Budapest
                                                 18 October 1991
 
                                                 HU ISSN 0374 - 0676


              FURTHER UBV OBSERVATION OF IU AURIGAE


IU Aurigae (B0p + B1p) is most interesting for its remarkable nature of
secularly increasing minima depths since the discovery as an eclipsing binary
in 1964 (Mayer, 1965). This phenomenon has been explained by an increasing
orbital inclination caused by precession of the orbital plane of the eclipsing
system. This precession must be due to presence of a third body in the system,
which was also suggested from a periodic variation of the light elements (Mayer
1971; Eaton 1978).

According to Eaton (1979), the orbital inclination is continuing to increase by
about 0.5 degree/year, and therefore, with 85deg for the inclination in 1979,
he suggested that the system may be in central eclipse in 1989. The same thing
has been also pointed out by Drechsel and Mayer (1987), with an increasing
inclination rate of 0.42 degree/year. In order to check whether this is the
case, UBV observations have been further carried out, in succession to the
author's previous observation in 1987-88 (Ohmori 1989). The present
observations have been made with the same 40-cm reflector at the Science Museum
of Kawasaki City during seven clear nights in 1989-90.

During the present observations, HD 35619 (BD+34d 1046) has been used as the
principal comparison star. The obtained measurements in mag(var) minus
mag(comp) are all plotted in Figure I. From the present light curve, we can
easily deduce amplitudes of 0.70m (U), 0.66m (B), 0.63m (V) for the primary
minimum and 0.52m (U), 0.49m (B), 0.48m (V) for the secondary as listed in
Table I together with all the previous relevant data. As an example, Figure 2
shows a plot of the minima depths in V between 1964 and 1990. It is easily
seen in Figure 2 that the minima depths are no longer secularly increasing
after 1986. The same tendency can be also seen in variations of the depths in
U and B as well. This result is in contradiction with the previous
prediction of central eclipse for 1989 by Eaton (1979) and Drechsel and Mayer
(1987).

                                  [FIGURE 1]

                  Fig. 1. Light curve of IU Aurigae in 1989-90.


Table 1       Eclipse depths (in mag.) of IU Aurigae

Observation   1964       1970        1973      1974     1976
year
                                                        Papousek
Observer      Mayer    Mayer       Mayer       Eaton    & Vetesnik
              (1965)   (1971)      (1976)      (1978)   (1982)

Prim. U       0.53      0.60        0.61      0.67       0.71
Min.  B       0.49      0.55        0.58      0.62       0.67
      V       0.48      0.54        0.56      0.60       0.63
Sec.  U                 0.46        0.47
Min.  B                 0.43        0.45                 0.50
      V       0.38      0.43        0.44                 0.48



Observation   1979        1983      1985     1988     1990
year                     Mayer
Observer      Eaton      & Jozef   Hui-song   Ohmori   This
              (1979)     (1983)    (1988)     (1989)   Paper

Prim.     U               0.74      0.80                0.70
Min.      B               0.68      0.74     0.66       0.66
          V   0.68        0.68      0.74     0.64       0.63
Sec.      U               0.57      0.62                0.52
Min.      B               0.55      0.57     0.52       0.49
          V   0.54        0.56      0.56     0.54       0.48


During the present observations, one epoch of the primary minimum has been
obtained as JD Hel 2447897.0575 with O-C = -0.1024d, which can be calculated
with Mayer's ephemeris (1987); JD Hel 2438448.4068 + 1.811474*E.

I would like to express my thanks to Prof. M. Kitamura of National 
Astronomical Observatory of Japan for his suggestion of the programme and kind
guidance.

                                  [FIGURE 2]

 Fig. 2. Variation of eclipse depths of IU Aur in V. Present observations
         by Ohmori are designated with double circles.



                SHIGEO OHMORI
                Member of Japan Amateur Photoelectric Observers
                Association (JAPOA)
                Science Museum of Kawasaki City
                Masugata 7-1-2, Tama-ku, Kawasaki City
                Kanagawa-ken, 214 Japan

References:

Drechsel, H., and Mayer, P.: 1987, Mitt. Astron. Ges., 68, 246. [BIBCODE 1987MitAG..68..246D ]
Eaton, J.A.: 1978, Acta Astron., 28, 63. [BIBCODE 1978AcA....28...63E ]
Eaton, J.A.: 1979, I.B.V.S., No. 1614.
Hui-song, T.: 1988, Chin. Astron. Astrophys., 12, 298. [BIBCODE 1988ChA&A..12..328H ]
Mayer, P.: 1965, Publ. Astron. Soc. Pacific, 77, 436. [BIBCODE 1965PASP...77..436M ]
Mayer, P.: 1971, Bull. Astron. Inst. Czech., 22, 168. [BIBCODE 1971BAICz..22..168M ]
Mayer, P.: 1976, Bull. Astron. Inst. Czech., 27, 308. [BIBCODE 1976BAICz..27..308M ]
Mayer, P., and Jozef, T.: 1983, I.B.V.S., No. 2407.
Mayer, P.: 1987, Bull. Astron. Inst. Czech., 38, 58. [BIBCODE 1987BAICz..38...58M ]
Ohmori, S.: 1989, I.B.V.S., No. 3333.
Papousek, J. and Vetesnik, M.: 1982, Scripta Fac. Sci. Nat. Univ. Brno,
      12, 435.