COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1909

                                  Konkoly Observatory
                                  Budapest
                                  1981 January 9

                                  HU ISSN 0374-0676


     V 758 Cen, LIGHT CURVE AND STUDY OF THE PERIOD



    The eclipsing binary V758 Cen was discovered by W. Strohmeier,
H. Ott and E. Schoffel (IBVS, No. 261, 1968); they also. published
25 times of photographic minima, and found a period P=0^d.5807835.
K. Chen (IBVS, No. 284, 1968) observed V758 Cen photoelectrically
(B) and derived a time of minimum light giving (O-C)=0^d.029 for
the elements determined by Strohmeier et al. Further, H. Bauernfeind 
(Veroff., Bamberg, Band VIII, 81, 1968) gave 118 minima
(and maxima); from these data he found a systematic trend for
the residuals in the interval JD 2415000-2430000 when comparing
the observations with Strohmeier et al. elements; suggesting a
somewhat larger period.
    In this note a V-light curve is presented from 500 UBV
photoelectric observations carried out at the Bosque Alegre Station 
of Cordoba Observatory with the 154 cm reflecting telescope
(Figure 1). The observations are given differentially in relation 


                         [FIGURE 1]


to the comparison star HD 120909 (B8). The light variation
shows a curved primary minimum and a flat secondary one,  thus
primary being a transit, while secondary is an occultation  due
to a slightly hotter component, so that the system may be classified 
as a type-A close (contact) binary.
Three times of minima were derived from each light curve
(U,B and V), also two minima were obtained  from Chen's photoelectric
observations. These minima are listed in Table I.

                	Table I
                   Minima of V758 Cen
Min.   Colour   J.D.hel      W  Cycles  (O-C)'  (O-C)
                (2400000+)
       B        39977.6959   3 -7620.0 -0.0017  0.0021
       B        39982.6358   3 -7611.5  0.0016  0.0053
II     V        44389.6313   3   -23.5  0.0015  0.0000
II     B        44389.6314   3   -23.5  0.0016  0.0001
II     U        44389.6321   2   -23.5  0.0023  0.0008
II     V        44392.5335   3   -18.5 -0.0002 -0.0017
II     B        44392.5334   3   -18.5 -0.0003 -0.0018
II     U        44392.5358   2   -18.5  0.0020  0.0006
I      V        44451.4806   3    83.0 -0.0028 -0.0043  
I      B        44451.4812   3    83.0 -0.0022 -0.0037
I      U        44451.4815   2    83.0 -0.0019 -0.0034

	From the photoelectric data only, the following least
squares ephemeris was found:
	P.M.= JD hel.2444403.2783 +0.5807850d*E
                         +-0.0004+-0.0000001      (p.e.)
	The cycles E,weights and residuals (O-C)' are given in
Table I.
	The photographic observations of Strohmeier et al. and
Bauernfeind quoted above were also analyzed together with  the
present material; weight W=1 was assigned to photographic values,
while W=3, 3 and 2 to the V,B and U minima. The least squares
light elements for all data (excluding maxima) are:
	P.M.- JD hel 2444403.2797 +0.58078556d*E
                   	 +-0.0012+-0.00000004	 (p.e.)
	The residuals (O-C) are also in Table I for photoelectric
minima; and for all observations including photographic values
(135 minima) are displayed in Figure 2.
It is noted that the period obtained from photoelectric
observations (7703 cycles) is very close to that found from all


                          [FIGURE 2]


the data (49791 cycles), and somewhat larger than that previously
found. The residuals are randomly distributed, so that the period
has been constant for the last 80 years.





                           S.L. LIPARI
                     Observatorio Astronomico and
                     I.M.A.F.
                     Laprida 854 - 5000 Cordoba
                     Argentina