COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 500

                                Konkoly Observatory
                                Budapest
                                1970 December 28


       A NEW LARGE AMPLITUDE ECLIPSING STAR

           In 1966, while examining variables in the Scutum
Star Cloud, V. M. Swain discovered this eclipsing binary at
18h43m11s, -5deg49.1' (1900), It is identified as v in Fig. 1,
where the comparison stars are also marked: a = 14.87,
b = 15.01, c = 15.60, d = 15.79, e = 16.82, f = 17.08,
g = 17.74, h = 18.03, k = 18.30, m = 18.53.

			[FIGURE 1]

           Though of photographic magnitude 15.3 at maximum
this star faded below the limit of the 110 24-inch Bruce plates
she inspected. In the autumn of 1966, Evered Kreimer obtained
13 useable negatives during two minima with a cold-emulsion 
camera and a 12.5-inch reflector, which he has described (1). 
Though the images of the variable were very weak at mid-minimum, 
they indicated a range of about three magnitudes and confirmed 
the period of 4.1 days.
     Fortunately this star was visible near mid-minimum
on four of 50 plates taken by A. Sandage with the 48-inch
Palomar Schmidt and made available to M. Harwood. From this
latter material, the minimum magnitude of the eclipsing
binary was determined to be 18.5, from the Kron Harwood (2)
and the photometric standards for NGC 6712 given by Sandage
and Smith (3).
     Since 10-minute exposures were used by Kreimer and
Sandage, little smearing of the light curve during primary
eclipse should be present. However, the Bruce exposures
were several times longer and were given half weight in
forming the normal points of primary eclipse (b = 0.3060 to
b = 0.4284 in Table I); it was also necessary to subtract
0.13 magnitude from these estimates to remove a systematic
difference. The Kreimer results were not used at all to form
the light curve, since his exposures were on panchromatic
film instead of a blue-sensitive emulsion.

			[FIGURE 2]

      The points in Fig. 2 denote the following: large
dots, the average of more than five estimates; small dots:
the average of five or fewer estimates; open circles: normal
points from the reflected observations. These data are
summarized in Table I, where n indicates the number of
estimates and MP  the mean phase computed from MP = p^-1
(JD - 2420000).

                       Table I.


   MP               m     n      MP               m       n
.0513             15.25  24   .3542/.3802       17.96     3
.1307             16.24   9   .3645/.3699       18.49     3
.2594             15.23  13   .4701             15.27     5
.3060/.4284       15.28   5   .5615             15.28    22
.3185/.4179       15.41   2   .9473             15.28    18
.3261/.4083       15.72   5   :7554             16.22     4
.3328/.4018       16.18   3   .8419             15.30    24
.3376/.3968       16.51   5   .9276             15.26     8
.3412/.3932       16.86   5


     The eclipses last 0.144p = 14.2h and are total with a
duration of 0.016p = 1.6h. The mean light curve during primary
eclipse was fitted to the individual observations to obtain
the four normal times of minima in Table II. The first two

                Table II.

   JD Hel.       E        O-C
2 428 198.598  -636      +.001d
   28 894.378  -487      -.003
   35 284.072  +1065     +.001
   39 401.140  +2065     +.001


are from Bruce plates, the third from 48-inch Schmidt
plates, and the last from Kreimer's negatives. The following
elements were derived: 
     JD min. hel. = 2430899.394 + 4.117068d E.


                      L. J. ROBINSON
                      M. HARWOOD
                      V. M. SWAIN

                   Cambridge, Mass. USA





(1)  John H. Mallas and Evered Kreimer, Sky and Telescope 33,
  285, 1967.        
(2) Margaret Harwood, Leiden Annals XXI, 387, 1962. [BIBCODE 1960AnLei..21..387H ]
(3) Allan Sandage and Lewis L. Smith, ApJ 144, 886, 1966. [BIBCODE 1966ApJ...144..886S ]