COMMISSION 27 OF THE I.A.U.
	INFORMATION BULLETIN ON VARIABLE STARS
		      NUMBER 316


					Konkoly Observatory
					Budapest
					1968 November 27



	THE ECLIPSING BINARY V78 IN OMEGA CENTAURI

	According to the proper motion, magnitude and apparent
position (Woolley, 1963) the eclipsing binary in the globular
cluster omega Centauri satisfies the membership
criteria as to be considered a member of the cluster.
Therefore, it turns out to be a very interesting object
since it is the brightest known eclipsing binary of extreme
population II. Consequently, in collaboration with Fourcade
and Laborde, we began observing this star with the 154 cm
telescope at Bosque Alegre Observatory. By means of 380
photographic observations published by Martin (1938) plus

                    [FIGURE 1]
	[Fig.1: Light curve of omega Cen. V78]

80 observations secured at Bosque Alegre and reduced to the
same system, the following times of minima were obtained:

		Minima				E	  O - C

	JDhel 2426470.3099 +/- 0.0067 m.e.     -3079     +0.009
	      2427895.4165 +/- 0.0036          -1859     -0.001
	      2427943.3090 +/- 0.0015          -1818     -0.002
              2427970.1714 +/- 0.0037          -1795     -0.007
              2440055.6397 +/- 0.0032          +8551     +0.001

A least squares solution gives the linear elements:

	Min + JD 2430066.9693  +  1.16812879 d  E
                    +/-0.0020  +/-0.00000047	p.e.

	The light curve shows a tipical EA with a shallow
(1/2) secondary minimum (fig. 1). A shape-depth relation and
a nomographic solution give the following photometric
orbital elements for a non-rectified preliminary solution:

	4_alpha^OC = 0.60	  i =  72.25deg
	          k = 0.80	r_s = 0.2812
                L_s = 0.7675	r_g = 0.3515
	        L_g = 0.2325	  x = 0.4 (assumed).

Cordoba Observatory
Laprida 854, Cordoba,
Argentina.
1968 November 18.			R. F. SISTERO

References:
Martin, W. C., 1938, Ann. van de Sterrenwachte Leiden, Deel XVII. [BIBCODE 1938AnLei..17B...1M ]
Woolley, R.V.d.R., 1963, Roy.Obs.Ann., No 2.