COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                      Number 2828

                                        Konkoly Observatory
                                        Budapest
                                        29 November 1985

                                        HU ISSN 0374 - 0676



           1985 - UBV LIGHT CURVES OF V508 OPHIUCHI


   V508 Oph (BD+13deg3496) is an uncommon eclipsing binary. Its variability
was first detected by Hoffmeister (1935) and Jacchia (1936), who classified
the star as a W UMa type eclipsing binary. Karetnikov (1963, 1977) obtained
photographic and photovisual light curves with amplitudes of the order of
1.1m in B and 0.7m in V. Further BV photoelectric observations by 
Rovithis and
Rovithis-Livaniou (1983) confirmed the mentioned peculiar amplitudes of light
variations. More recently, Lapasset and Funes (1985) could not corroborate
the previous photometric behaviour of V508 Oph from UBV data. Their 1984-
observations showed normal W UMa type light curves with depths of minima of
about 0.80m, 0.86m and 0.94m in V, B and U, respectively. The few 
observations made only partially covered the orbital cycle.
   In this note, new photoelectric data obtained at El Leoncito Observatory
(San Juan, Argentina) during the 1985 - winter season are presented. They
were performed by means of a 76-cm reflector telescope, an RCA 34031(A)
photomultiplier refrigerated by Peltier effect and photon-counting electronics. 
Standard UBV filters were also employed. The measurements were made
differentially with respect to the comparison star BD + 13deg3495. All the
observations were corrected for first and second order differential extinction 
using mean coefficients For El Leoncito.
   A total of 249 UBV observations were derived and from them four new times
of minima were calculated. The total of 11 photoelectric minima derived from
Rovithis-Livaniou and Rovithis (1983), Lapasset and Funes (1985) and the
present data, were used to deduce the following linear least squares 
ephemeris:
      Min.I. (J.D.hel.) = 244478.3251 + 0.34479444d*E                    (1)
                              +-.0005 +- .00000019

Comparing this equation with the older ephemeris given by Karetnikov (1977):

      Min.1. (J.D.hel.) = 2428416.3342 + 0.344791922d*E                  (2)
                               +-.0002 +- .000000012

there seems to be a small increment in the orbital period. This will be studied
in detail and published elsewhere.


                              [FIGURE 1]

             Figure 1. UBV light curves of V508 Ophiuci


     Table I. Photoelectric times of minimum of V508 Oph
   Min  J.D.hel.        E            O-C     Reference
        2440000.+

   II   4783.4265      -5.5        -0.0022        A
   II   4784.4623      -2.5        -0.0008        A
    I   4785.3283       0.0         0.0032        A
   II   4785.4958       0.5        -0.0017        A
    I   4786.3623       3.0         0.0028        A
    I   4864.2816     229.0        -0.0014        A
    I   5915.5615    3278.0         0.0003        B
    I   6239.6684    4218.0         0.0003        C
    I   6240.7035    4221.0         0.0011        C
   II   6241.5635    4223.5        -0.0009        C
    I   6241.7362    4224.0        -0.0006        C
References to Table I:

    A: Rovithis-Livaniou and Rovithis (1983)

    B: Lapasset and Funes (1985)

    C: Lapasset (this work)



  Equation (1) was used to calculate the phases of all the observations
and the residuals (O-C) listed in Table I. The light curves of V508 Oph 
derived from 1984-85 observations are shown in Figure 1. The presumptions
exposed by Lapasset and Funes (1985) are here confirmed: the present UBV data 
show a normal behaviour of W UMa type stars. Depths of primary minima are 
about 0.81m, 0.85m, 0.92m in V,B and U respectively. The differences 
between primary and secondary minima are about 0.10m. Thus the conclusions 
of the mentioned paper are still valid: since errors can be assumed for   
neither the older nor the present data, it has to be believed that a sudden 
change has actually occured to V508 Oph between 1981 and 1984.
   The author is very grateful to the Director of the Felix Aguilar Observatory
(San Juan) for granting the running time at El Leoncito Observatory.



                                              E. LAPASSET

                                         Observatorio Astronomico 
                                         de Cordoba and CONICET 
                                         Laprida 854
                                         5000-Cordoba - Argentina



References: 

Hoffmeister, C., 1935, Astron. Nachr., 255, 405. [BIBCODE 1935AN....255..401H ]
Jacchia, L., 1936, Astron. Nachr., 261, 212.  [BIBCODE 1936AN....261..211J ]
Karetnikov, V.G., 1963, Perem. Zvezdy, 14, 348. [BIBCODE 1963PZ.....14..348K ]
Karetnikov, V.G., 1977, Perem. Zvezdy, Suppl., 3, 247.  [BIBCODE 1977PZP.....3..247K ]
Lapasset, E., and Funes, J.G., 1985, Astrophys. Space Sci., (in press) [BIBCODE 1985Ap&SS.113...83L ]
Rovithis, P., and Rovithis-Livaniou, H., 1983, Astrophys. Space Sci., 96, 283. [BIBCODE 1983Ap&SS..96..283R ]
Rovithis-Livaniou, H., and Rovithis, P., 1983, Inf. Bull. Var. Stars., No. 2317