COMMISSION 27 AND 42 OF THE IAU
                   INFORMATION BULLETIN ON VARIABLE STARS
                               Number 3803

                                                         Konkoly Observatory
                                                         Budapest
                                                         12 November 1992

                                                         HU ISSN 0374 - 0676


            NEW PHOTOELECTRIC MINIMA TIMES OF V505 SAGITTARII

In a recent report (Rovithis-Livaniou et al., 1991) the behaviour of the period
of the eclipsing binary V505 Sagittarii was studied and new ephemeris formulae
were proposed. Since most of the recent minima times were visual - exhibiting
large scattering - we had call for new (and especially photoelectric) minima
times. This was done during our recent observations of V505 Sgr, which were
made using the 48 inch Cassegrain reflector at the Kryonerion Astronomical
Station of the National Observatory of Athens, Greece. The star HD 187664 was
used for comparison and reduction of the observations was made in the usual way
(Hardie, 1962). During our observations three minima times were obtained and
are presented in Table I, the successive columns of which give: the Hel. JD;
the (O-C)_C according to the linear ephemeris of Chambliss (1972); the (O-C)_M
according to Kholopov's et al. (1985) ephemeris formula and finally (O-C)_R1
and (O-C)_R2 according to our linear ephemeris formulae. (Equations (1.5) and
(1.7) in Rovithis-Livaniou et al., 1991).


                                 Table 1

              Hel. JD    (O-C)_c   (O-C)_M   (O-C)_R1  (O-C)_R2

              432.4871   0.0199   -0.0034   +0.0007    0.0013
              442.5402   0.0189   -0.0047   -0.0006    0.0000
              804.4984   0.0195   -0.0052   -0.0004    0.0001

   From the values of both (O-C)_R1 and (O-C)_R2 it is obvious that the
proposed new ephemeris formulae hold good. But if one wants to have a more
accurate view and adds the 3 new minima times - given in Table I - to those of
Chambliss (1972) and Rovithis-Livaniou et al., (1991), then some minor
variations are found, thus:

Chambliss' (1972) linear ephemeris formula is improved to:

       Min I = 2425501.3811 + 0.182869342d x E      (1.1)


while Kholopov's et al. (1985) to:

       Min I = 2444461.5929 + 0.18286938d x E       (1.2)

continuing their changes.

   Moreover, since there are only 3 secondary minima times for V505 Sgr in the
literature, and the scatter in the primaries is too large, one cannot examine
them separately now.
   Concluding, we ask for more accurate (photoelectric) minima times - both
primaries and secondaries - which together with more data for the third
companion (e.g.  Khalesseh and Hill, 1991; Tomkin, 1992) will lead to the
evaluation of the light-time effect which must be removed from the (O-C)
diagram of V505 Sagittarii.


                                 H. ROVITHIS-LIVANIOU
                                 Section of Astrophysics,
                                 Astronomy and Mechanics,
                                 University
                                 GR 157 84 Zografos
                                 Athens, Greece

                                 P. ROVITHIS
                                 Astronomical Institute
                                 National Observatory
                                 of Athens
                                 P.O. Box 20048
                                 11810 Athens, Greece



References:

Chambliss, C.R., 1972, Astron. J. 77, 672. [BIBCODE 1972AJ.....77..672C ]
Hardie, R.H., 1962, in W.A. Hiltner (Ed.), "Stars and Stellar Systems" Vol. II,
    Astronomical Techniques, The University Chicago Press, Chicago.
Khalesseh, B. and Hill, G., 1991, Astron. Astroph. 244, 75. [BIBCODE 1991A&A...244...75K ]
Kholopov, P.N. et al., 1985, Fourth Edition of the General Catalogue of
    Variable Stars, Moscow.
Rovithis-Livaniou, H., Antonopoulou, E., Rovithis, P. and Kalimeris, A., 1991,
    IBVS No. 3608.
Tomkin, J., 1992, Astrophys. J. 387, 631. [BIBCODE 1992ApJ...387..631T ]