COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 3325

                                      Konkoly Observatory
                                      Budapest
                                      9 May 1989

                                      HU ISSN 0374 - 0676


              1987 LIGHT CURVES OF BX ANDROMEDAE


BX And (BD +40d4421), a near-contact binary with the Beta Lyrae type light
curves is the brighter companion of the visual binary ADS 1671. The system has
been observed frequently, since 1950's by many authors (see Samec, Fuller and
Kaitchuck (1988), and Castelaz (1979) for the references). Chou (1959) and
Ahnert (1975) reported that BX And has undergone around 1950, a major period
change of about 0.25s. A new abrupt period change in 1981 has been reported by
Gulmen et al. (1988) who also obtained the new light curves (in B and V) of the
system. Having late type (F2V) active components in near contact, the system's
total light at maximum and/or minimum is expected to vary in time. To study
the light curve variations, we thus included the system in our observing
program.

The present observations were made on two nights in October, four nights in
November, and two nights in December, 1987 using an EMI 9789QB photomultiplier
attached to the 30 cm Maksutov telescope of the Ankara University Observatory.
The differential observations in three colors were made with respect to the
comparison star BD +39d0476. BD +39d0484 was used as the check star. The
third light (from the other component of the visual binary ADS 1671) could not
be excluded in the brightness measurements of the variable star. Thus, 175
differential observations were obtained in each V, B and U filters. The
observations were corrected for differential extinction and light time effects,
and are shown in Figure 1. as delta m-(var.-comp.) versus phase. The light
elements used in phase calculation were given by Chou (1959), as

Hel. JD MinI=2436528.7777*0.61011534d E


                             [FIGURE 1]

 Figure 1. Light curves of BX And defined by the individual observations.


The times of two new primary and two new secondary minima (see Table.1) confirm
the second abrupt decrease of 0.25 sec. in the period, which was reported by
Gulmen et al. (1988). The light curve variation seems larger in the secondary
minimum. The large difference between the depth of the minima and the
reddening of the color curves in the primary minimum indicate considerably
different temperatures for the component stars. Thus, at least one of the
component stars of the system should not be completely contact with the first
critical Roche lobe, and the common convective envelope (if present) around the
component stars is not effective to equalize the temperatures.

Table 1.

The new times of minima of BX And.

Hel.Min             No. of Obs.   Filter   Remark
211700+
093.5234+-0.0010      21           U        Min I
   .5236+-0.0007      29           B        "
   .5224+-0.0006      17           V        "
094.4408+-0.0023      35           U        Min II
   .4409+-0.0010      33           B        "
   .4367+-0.0006      34           V        "
116.4075+-0.0025      28           U        Min II
   .4059+-0.0012      25           B        "
   .4049+-0.0019      27           V        "
117.3202+-0.0004      16           U        Min I
   .3185+-0.0005      16           B        "
   .3191+-0.0007      16           V        "

We thank to M. Ozcelik, for the generous help during the observations.


ETHEM DERMAN
AYVUR AKALIN
OSMAN DEMIRCAN
Dept. of Astronomy and Space Sciences,
University of Ankara.
06100 Tandogan, Ankara, TURKEY.

References :

Ahnert, P., 1975. Mitteilungen Uber Veranderliche Sterne. 6. 189. [BIBCODE 1975MitVS...6..189A ]
Castelaz. M., 1979, I.B.V.S. No. 1554.
Chou, K.C., 1959, Astron. Journal, 64, 469. [BIBCODE 1959AJ.....64..468C ]
Gulmen, O., Gudur, N., Sezer, C., Eker, Z., Keskin, V. and Kilinc. B., 1988,
   I.B.V.S. No. 3266.
Samec, R.G., Fuller, R.E., and Kaitchuck, R.H., 1988, I.B.V.S. No. 3230.