COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                   Number 1306


                                  Konkoly Observatory
                                  Budapest
                                  1977 July 21




       PHOTOMETRY AND A PRELIMINARY ANALYSIS OF THE
          BETA-LYRAE LIKE SYSTEM HD 173 198




    As a part of an observational program on binary systems
of Beta-Lyrae type HD 173198 was observed photoelectrically
with UBV filters during the 1976 southern winter at the Abrahao
de Moraes Observatory in Valinhos (Sao Paulo state-Br.).
    The first observations on this system were reported by
Leewen (1975). From the epoch of the principal minimum observed 
by us and from that given by Leewen, we have improved the
period of the system, which is now given as follows
                P = 1.364076+-0.000001 d.
    The observations reported presently were carried out with
the 61 cm telescope of the Sao Paulo University at Valinhos, 
using photon counting techniques and a data acquisition system 
operated by a Nova computer. The observations were reduced 
following the standard techniques and Figure 1 shows the light curve
in the B color.
    The main comparison star was HD 173003 (B5) whose colors,
obtained from absolute photometry in two nights, are
    V = 7.72m +- 0.01m;(B-V) = 0.43m +- 0.01m; (U-B) =-0.12m +- 0.02m.
As a check star, was used HD 172850 (B9, 8.2m).
    The light curves in B and V colors were rectified by the
Russel and Merril (1952) method and we have followed Kopal (1959),
taking into account the shape of the minima in order to determine
the function chi(x,k,alpha0,n). We have considered an average value
of chi for several points instead to take only one point in each
eclipse.

    The elements of the system obtained from this analysis,

         Table   1
Color  L1   L2       r1   r2    i
V    0.679 0.321   0.432 0.326 81d
B    0.672 0.328   0.433 0.325 81d


                       Table   2
Star   Color      ra      rb      rc    Te(Kdeg)     L       m1/m2
1        V       0.516   0.450   0.411   22,000     0.658     1.25
2        V       0.344   0.331   0.321   20,210     0.341
1        B       0.516   0.450   0.411   22,000     0.666     1.25
2        B       0.344   0.331   0.321   20,154     0.333


                  Table 3
            Star Type m/msun R/Rsun (B-V)0
             1    B1  14.1   6.9    -0.23
             2    B2  11.2   5.0    -0.21

                     [FIGURE 1]

namely, the normalized luminosity, relative radius and orbital
inclination are given in Table 1.
    We have also analysed the light curves through the Wood's
model (1971 and modifications 1973-1976). The computations, 
following the numerical code developed by Wood, were started 
using as initial parameters those obtained previously through the
Russel-Merril method.
    The astrophysical parameters obtained directly from our
computations are given in Table 2. Main sequence calibration
allows us to estimate the individual masses and absolute 
dimensions, using Kepler's third law. These data are shown in Table 3.

    The total visual extinction was estimated to be AV=1.5m
and the distance is about 1.0 kpc.

    A more detailed analysis of this system will be presented
elsewhere.



                                   J.A. de FREITAS PACHECO *
                                   CHARLES RITTE **
                                   A. DAMINELI NETO **
            
                                   Instituto Astronomico
                                   e Geofisico, Depto.Astronomia
                                   Universidade de Sao Paulo
                                   Caixa Postal 30627-Sao Paulo
                                   Brasil


References:

Kopal, Z. 1959 in Close Binary Systems [BIBCODE 1959cbs..book.....K ]

Leewen, von F. 1975, IBVS No. 1041

Russel, H.N. and Merril, J.E. 1952, Contributions from the
      Princeton University Observatory No. 26 [BIBCODE 1952deeb.book.....R ]

Wood, D.B. 1972, A Computer Program for Modeling Non-Spherical
      Eclipsing Binary Star Systems-Goddard Space Flight Center
      Modifications included are those which have appeared in
      "Wink Status Report" from No. 1 to No. 7





* Present Address - Observatoire de Nice - Le Mont Gros - Nice,
              France

** Partially supported by Fundacao de Amparo a Pesquisa do Estado
             de Sao Paulo