COMMISSION 27 OF THE I.A.U.
       INFORMATION BULLETIN ON VARIABLE STARS
                   Number 1554

                                 Konkoly Observatory
                                 Budapest
                                 1979 February 19




      PHOTOELECTRIC UBV LIGHT CURVES AND PERIOD
          DETERMINATION OF BX ANDROMEDAE


    The variable nature of BX Andromedae (=ADS1671A=HD 13078
=BD+40d442=SVS 995 And) was announced by Soloviev (1945). Observed 
times of minima have been published by Soloviev (1945),
Ashbrook (1951, 1952, 1953), Svolopoulos (1957), Chou (1959),
Oburka (1965), Robinson (1965), Pohl and Kizilirmak (1970,1974),
and Meyer (1972). Light elements have been published by Ashbrook
(1951), Svolopoulos (1957), and Chou (1959).
    Kukarkin (1969) listed BX And as a W Ursae Majoris type
system. W UMa systems are defined as close eclipsing binaries
that have periods less than one day. They often show period variations 
and variation in maximum and minimum magnitude from cycle
to cycle. Furthermore, VW Cephei, another W UMa star has recently
found to be an X-ray source (Cruddace, Dupree and Carroll, private
communication).
BX And is a relatively bright W UMa system well placed for
northern observers. Chou (1959) reported that BX And apparently
underwent a period increase in 1952. To study this effect, new
UBV observations of BX And were obtained on October 26/27 and
27/28, 1978 and all available previous observational material
collected. Because BX And shows some of the same characteristics
as VW Cephei, observations are published at this time.
     UBV photoelectric observations were made with the Yerkes
Observatory 61cm reflector using a refrigerated 1P21 photomultiplier 
and pulse counter. BD+39d476 was used as the comparison
star. BD+39d481 and BD+39d484 were used as check stars. One
primary minimum and one secondary minimum were observed. The
Julian dates were respectively, 2443809.8873 and 2443809.5705
(+-0.0005).

                         [FIGURE 1]

  Fig. 1. O - C diagram for the times of minima calculated using the
  period 0.61011508d

                         [FIGURE 2]

  Fig. 2. UBV observations of BX And on 1978 Oct. 26/27 (crosses)
  and Oct. 27/28 (dots)

     The new times of minima allow the period and ephemeris to
be improved. Combining these observations with the previous material 
gives the following elements:

       Hel JD MinI= 2443809.8873 + 0.61011508d*E

Figure 1 shows the residuals of observed minima for BX And computed 
from the above elements. The few available secondary minima
timings are also shown, displaced 0.5 in phase. It is seen that
a definite period change occurred between JD 2424000 (1924) and
JD 2427360 (1936). There is some indication, especially from the
secondary minima, of a period variation around 2433500 (1950).
     Figure 2 shows the magnitude difference between BX And
and the comparison star BD+39d476 versus phase. The light curves
indicate depths of the two minima of about the two minima of
about 0.65m and 0.30m in each color. Comparison of the two nights
of observation shows apparent variation in the magnitude at maximum. 
No similar difference between the two nights was found for the
check star. Also, anomalous spikes near primary minimum were 
observed in all colors. The large decrease in magnitude (about 0.1m
in the V, 0.2m in the B, and 0.3m in the U) occurred in less than
one minute. No instrumental problem could be found and the effect
was apparently real.
    The author wishes to extend his gratitude to Dr. L. Hobbs
and the staff of Yerkes Observatory for the allotment of observing 
time and their assistance, and Dr. W. Osborn whose suggestion
and comments for the paper are greatly appreciated.




                          MICHAEL CASTELAZ
                          Department of Physics
                          Central Michigan University
                          Mt. Pleasant, Michigan 48859,
                          U.S.A.




References:

Ashbrook, J., 1951, Astron.J., 56, 54 [BIBCODE 1951AJ.....56...54A ]
Ashbrook, J., 1952, Astron.J., 57, 259 [BIBCODE 1952AJ.....57..259A ]
Ashbrook, J., 1953, Astron.J., 58, 171 [BIBCODE 1953AJ.....58..171A ]
Chou, K.C., 1959, Astron.J., 64, 468 [BIBCODE 1959AJ.....64..468C ]
Kukarkin, B.V.,et al., 1969, "Gen.Cat.of Var.Stars", 3rd ed., Vol. 1 [BIBCODE 1969gcvs.book.....K ]
Meyer, A., 1972, I.B.V.S. No. 668
Oburka, O., 1965, Bull.Inst.Czechoslovakia, 16, 212 [BIBCODE 1965BAICz..16..212O ]
Pohl, E. and Kizilirmak, A., 1970, I.B.V.S. No. 456
Pohl, E., and Kizilirmak, A., 1974, I.B.V.S. No. 932
Robinson, L.J., 1965, I.B.V.S. No. 119
Soloviev, A., 1945, Astr.Circ.Acad.USSR, No. 44
Svolopoulos, S.N., 1957, Astron.J., 62, 330 [BIBCODE 1957AJ.....62..330S ]