COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                          Number 3493

                                              Konkoly Observatory
                                              Budapest
                                              19 July 1990

                                              HU ISSN 0374 - 0676



   V 577 Oph - AN ECLIPSING BINARY WITH A DELTA Sct TYPE PRIMARY COMPONENT

   The eclipsing variable V 577 Oph = BD +6 3679 was included in our 
observational program due to its considerable eccentricity e = 0.22 (Shugarov, 
1985). The observations were carried out in Tian-Shan Observatory 
(altitude 3000 m) using a photoelectric photometer (EMI 9863) attached to the
19" reflector in 1987 - 1990. Three nearby stars were selected as comparison
stars: BD +6d3678 = "K" (prime standard), BD +6d3680 = "C1", BD +6d3677 =
"C2". The differential observations were transformed to the WBVR system 
using HD 165401 standard star (Khaliullin et al., 1985). All observations
were corrected for atmospheric extinction. The mean observational error in
"V" is + 0.005. The comparison stars are constant within + 0.008 
interval.
   The pulsations were detected after previous processing of the photoelectric 
data. So we have undertaken special patroling of the star in quadratures. 
The analysis of all observations with our computer programs has 
revealed the presence of stable in 2.5 year interval period:

           JDhel(max) = 2447620.379 + 0.0694909d * E
                                          +/- 3

   Light curve in quadratures folded with this period is given in Figure
1. Observations in other filters are in good agreement with this value of
the period. The amplitudes of light variation in different filters are:
"W" - 0.055m, "B" - 0.070m, "V" - 0.052m, "R" - 0.040m. The amplitude is largest
in "B" and decreases to "R". The pulsations just disappear in the primary
minimum and have almost double amplitude in the secondary one. This 
indicates that the primary (brighter) component of the system is a delta Sct
variable.
   As the pulsations do not completely disappear in primary minimum, we
have averaged all available points near mid-eclipse, where physical variability 
is less. Then we derived the individual moments of primary minima by
titting this mean curve to the observational points in computer memory.
These moments are presented in Table I. The mean error is +/- 0.0004 day. The

  Table I. Photoelectric times of primary minimum of V 577 Oph

  JD hel          E      O-C
  2400000.0+
  47023.21267 	-63   -0.00054
  47272.4560  	-22    0.00035
  47327.16767 	-13    0.00026
  47345.40402 	-10   -0.00064
  47406.19552     0    0.00002

Table II. Mean magnitudes of the stars

Star		 V      B-V     W-B     B-R

K              9.417   0.554   0.102   1.056
C1             9.693   0.212   0.022   0.405
C2             9.756   1.118   0.925   2.040
V 577 Oph:
quadrature    10.978   0.488   0.085   0.932
Min I         11.621   0.504   0.000   0.991
Min II        11.487   0.509   0.080   0.977

following formula for primary minima was obtained from this Table, making
use of the least-squares method:

       Min I  JDhel = 2447406.1955 + 6.079084d * E


                                [FIGURE 1]

            Figure 1. Light curve in quadratures of V577 Oph

                                [FIGURE 2]

                       Figure 2. Primary minimum

                                [FIGURE 3]

                      Figure 3. Secondary minimum


         
   The moments of the secondary minimum cannot be obtained precisely because
of the significant distortion of the light curve in the minimum due to pulsations.
The phase of this minimum derived from all our observations is phi= 0.578 p. 
The durations of minima are: DI= 0.0468p, DII= 0.0538p. Assuming
i = 90deg we can estimate the eccentricity e= 0.14 and omega= 29.6. Both minima
are presented in Figures 2 and 3. Mean magnitudes and colours of the variable
in quadratures and in minima and those of comparison stars are presented
in table II. It is interesting to note that the variable becomes redder in
both minima. So one can suppose a faint red companion not farther than 6"
from the main components (third body?), as the angular diameter of diaphragm
in use was 12".


I.M. VOLKOV
Sternberg State's Astronomical Institute
USSR, Moscow, 117899, Universitetsky 13

References:
Khaliullin, Kh.F., Mironov, A.V., Moshkalev, V.G.: 1985, Astrophys. Space
	Sci., 111, 291 [BIBCODE 1985Ap&SS.111..291K ]
Shugarov, S.Yu.: 1985, Astron.Circ. USSR, No. 1359 [BIBCODE 1985ATsir1359....4S ]