COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1941
                                
                                  Konkoly Observatory
                                  Budapest
                                  1981 March 25

                                  HU ISSN 0374-0676



         ON THE PERIOD OF LIGHT VARIATION
         IN THE RS CVn  SYSTEM HD 86590


   The suspected variability of the spectroscopic binary HD
86590 has recently been confirmed by Hall, Vaucher, and Louth
(1), whose photoelectric observations made early in 1979 show
a nearly sinusoidal wave when plotted with respect to the
spectroscopic period of 1.070354d by Bolton (2). The
photoelectric observations in 1976 by Bolton and his colleagues
confirm the presence of the wave but the phasing is different
(2).
   The system has been on our observing program at the
University Observatory at Ankara since 1975; the aim was to
look for possible eclipses and variability. Although no
observations, however, could be obtained since 1977, it will
be useful to give an account of these observations in the
light of the recent results mentioned above.
   We have 321 observations in v and 226 observations in b
on a total of 16 nights in two seasons between January 1975
and May 1977 obtained with the 30-cm maksutov telescope with
an EMI 62565 photomultiplier.
   The observations in v are plotted in Fig.1a with respect
to the spectroscopic period quoted above: The phases are
calculated using the spectroscopically adjusted epoch (2),
JD 2442849.896, so that the primary eclipse should fall at
phase 0.0. The instrumental magnitudes are relative to the
comparison star HD 86132. They are corrected for differential
extinction when necessary. Each point in the figure
corresponds to the mean of up to 10 individual observations.

                        [FIGURE 1]

The mean standard error of a single differential measure,
obtained using the two check stars HD 86418 and HD 85428 and
the comparison star, is about +- 0.012m in both colours.
   The light curve has a full amplitude of 0.14m in v and
0.16m in b, which, apart from any scale differences, agree
well with other observations (1,2,3,). But it is seen from
Fig.1a that our observations, which are spread over a longer
interval of time than those by Hall et al.(1), do not fit the
spectroscopic period: 1976 observations, shown as crosses,
depart the most while observations on different nights in
1977 fall systematically above or below each other on the
descending branch of the light curve. We have looked for
systematic errors between the seasons and between nights but
found none. The nightly mean differences between the two check
stars, and between a check star and the comparison star, have
a standard deviation of only +- 0.005m in v and +- 0.006m in b
(up to 15 observations of a check star are available on a
given night). Therefore, unless there are intrinsic variations
of the order of weeks,or even days ,over and above long term
changes and wave migration encountered in similar objects, it
is possible that the photometric period is different from the
spectroscopic period.
     We have two approximate times of minima JD 2443194.475
and 2443225.45. These, plus that given by Hall et al.(1),
namely 2443969.85, imply a period of 1.06950d. The observations
plotted against this period and the same epoch as before are
shown in Fig.1b. The mean wave is better defined but there are
observations on two nights in 1976 that fall below the curve
around the phase 0.6. It is interesting to note that the
phase of a possible eclipse considered by Hall et al. falls
here, but the phasing of the points suggests against an   
eclipse and it is possible that the period is still wrong.
     A better fit is achieved with a period twice as long,
viz., 2.13899d. This is shown in Fig.2 in both colours. The
minimum observed by Hall et al.fits nicely at phase 0.59.
This period also satisfies the BV observations by Bolton and
co-workers with a phase shift of about 0.09. Clearly this long
period variation, if real, can not be due to eclipse and such
a double wave is not expected. The observations around the           
phases 0.05 and 0.35 which vary in the wrong direction might
point to the period as being still wrong. More observations          

                     [FIGURE 2]

are needed to eliminate spurious periods and to study the
light curve changes. Observations of this system will be
continued.



                            Z. ASLAN
                      University Observatory
                        A.U. Fen Fakultesi
                          Ankara, Turkey




References:
1.   D.S. Hall, C.A. Vaucher, and H. Louth, 
     Inf. Bull.Var. Stars, No. 1690, 1980
2.   C.T. Bolton, Z. Aslan, K.W. Kamper, and K.W. Lyons, 1981
     submitted to Astronomical Journal [BIBCODE 1981AJ.....86.1267B ]
3.   O.J. Eggen, Inf. Bull. Var. Stars, No. 1426, 1978