COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                          Number 3666

                                                  Konkoly Observatory
                                                  Budapest
                                                  3 October 1991

                                                  HU ISSN 0374 - 0676


              PHOTOELECTRIC LIGHT CURVES OF HU AURIGAE


The twelfth magnitude variable star HU Aur was first discovered at the Bamberg
Observatory as BV 83 (Geyer et al. 1955), and subsequently observed by
Filatov (1960) and Strohmeier et al. (1962). However, no photoelectric light
curves have been reported so far. In the fourth edition of GCVS (Kholopov et
al. 1985), the system is classified as EB/KE. The ephemeris for the primary
minimum has been given by Strohmeier et al. (1962) as

       Min I = HJD 2426707.390 + 1.408010d E.          (1)

In 1989-1991 we performed photoelectric observations of the system with the
91-cm reflector at the Dodaira Station of the National Astronomical Observatory
of Japan. The equipment employed is a multi-channel polarimetric photometer,
whose detailed description is given by Kikuchi (1988). The nearby C1 and C2
(BD+34d 897) stars in Figure 1 were chosen as the comparison stars.


                                [FIGURE 1]

 Figure 1. Finding chart of HU Aur. The variable HU Aur is
           represented by the open circle. The comparison stars
           are designated as C1 and C2.

                                [FIGURE 2]

 Figure 2. Light curves of HU Aur. The effective wavelengths
           of the channels 3, 4 and 5 are 460, 535 and 650 nm,
           respectively.


We have calculated the differential magnitudes of HU Aur with respect to C1,
taking into account the differential magnitudes of C2 relative to C1. The
light curves are shown in Figure 2 for some channels, where the orbital phases
are calculated from the above ephemeris. As is seen in Figure 2, the depths of
both minima are almost the same, as predicted by Strohmeier et al. (1962):
the shape of the light curves are not EB-type. The colour of the system
reveals that HU Aur is not so an early-type system. We have roughly estimated
the spectral type of HU Aur to be middle to late F (at light maxima), comparing
the colour of HU Aur with the colours of some standard stars taken with the
same photometric system.

We caught primary minima twice in our observations, one on October 9 and the
other on December 20 in 1989. The times of mid-eclipse have been estimated to
be HJD 2447809.1997 (for October 9) and HJD 2447881.0090 (for December 20).
According to the ephemeris (1), these yield the O-C values of -0.0162d (E =
14987) and -0.0154d (E = 15038), respectively.

Because the ephemeris (1) has been derived based on photographic
observations, we recalculated the ephemeris including our photoelectric primary
minima. Assigning weight 1 to photographic observations and 10 to
photoelectric ones, we have obtained the following ephemeris,

       Min I = HJD 2447809.199 + 1.4080103d E.         (2)
                           +-6         +-8

In deriving this, we did not use the data for secondary minima, because it has
been reported that these minima occurred slightly out of the mid-phase 0.5p
(Strohmeier et al. 1962). The O-C values of the observed primary minima are
calculated from the new ephemeris (2) and listed in Table I.

The new orbital period is essentially the same as the old one. This indicates
that there has been no period change since the observations by Strohmeier et
al. (1962) and the system is probably a detached one, though there seem some
indications of proximity effect in the light curves. Therefore, the
classification KE in GCVS is surely not an appropriate one.

                  Table I

The O-C values of primary minima

Observed minima    E       O-C (d)    Source
HJD 2426707.332   -14987   -0.017    Strohmeier et al.
           .353   -14987   +0.004    S
       6987.567   -14788   +0.024    S
       7397.358   -14497   +0.084    S
       7449.379   -14460   +0.009    S
       9168.526   -13239   -0.025    S
       9175.527   -13234   -0.064    S
   243 3157.410   -10408   -0.034    Filatov
       3181.460   -10389   +0.080    F
       3916.336   -8867    -0.026    P
       5503.191   -8740    +0.002    F
       5510.189   -8735    -0.040    F
       5548.189   -8708    -0.077    F
       6756.126   -7978    +0.033    F
       6853.476   -7781    +0.005    F
       7705.341   -7176    +0.024    Strohmeier et al.
   244 7809.1997      0    +0.0006   Present work
       7881.0090     51    +0.0014   Present work


Yasuhisa NAKAMURA
Noboru KONTOH*
  Department of Science Education
  Faculty of Education, Fukushima University
  Fukushima, 960-12 JAPAN
*):Present address
  Minami-Aizu Senior High School
  Nango-mura, Minami-Aizu-gun
  Fukushima, 967-06 JAPAN

REFERENCES

Filatov, G.S. 1960, Astron. Tsirk., No. 215, 20. [BIBCODE 1960ATsir.215...20F ]
Geyer, E., Kippenhahn, R. & Strohmeier, W. 1955, Kleine Veroff.
  Remeis-Sternw. Bamberg, No. 11.
Kikuchi S. 1988, Tokyo Astron. Bull., 2nd ser., No. 281.
Kholopov, P.N. et al. 1985, General Catalogue of Variable Stars,
  4th ed., Vol. I (Nauka, Moscow).
Strohmeier, W., Knigge, R. & Ott, H. 1962, Veroff. Remeis-Sternw.
  Bamberg, 5, No. 13.