COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3436

	                                Konkoly Observatory
         	                        Budapest
                 	                1 March 1990
	
                      	                HU ISSN 0374 - 0676



     V 3903 SAGITTARII: ANOTHER O-TYPE ECLIPSING BINARY

   V 3903 Sgr (HD 165921, CD -24d 13962, SAO 186366) is located 
in the region of the open cluster Collinder 367 (Claria,
1976) and is a possible member of the R association Simeis 188
(Herbst et al., 1982). It is classiffied as a spectroscopic 
binary (Conti and Alschuler, 1971) with components of early 
spectral type (O7 and O9, Niemela and Morrison, 1988). Cousins
(1973) and Claria (1976) have both found variations in the
brightness of the system with amplitude of 0.16 mag in V, but
no light curve has been published.


                          [FIGURE 1]


   As a part of a Brazilian-Danish-Spanish project of studies
of eclipsing binaries this star was observed on 8 nights, from
June to August 1989, using a conventional one-channel photoelectric 
photometer with the ZEISS (JENA) 60 cm telescope of the
Laboratorio Nacional de Astrofisica (LNA-CNPq-SCT), Brasopolis,
MG, Brazil. The light curve shown in the figure was obtained
using the following ephemeris, with the period determined
using the method of Lafler and Kinman (1965, with all 4 colours), 
and the time of minimum determined by means of a 2nd
degree polynomial :

              Min I = 2447691.683 + 1.7440d E
                             +/-l     +/-1

    The period determined from our photometric observations is
not very different from the spectroscopic one given by Niemela
and Morrison (1988), of 1.744215+/-0.000005 day.
    More observations are being reduced, and we plan to obtain
further photometric data for a complete study (period, times of
minima and photometric elements), which will appear elsewhere.


       N.C.S. CUNHA (1), L.P.R. VAZ (1), C.M.M. POSSA (1),
             BODIL E. HELT (2), J.V. CLAUSEN (3)

(1) Depto. de Fisica-ICEx-Universidade Federal de Minas Gerais
   Caixa Postal 702 - CEP 30.161 - Belo Horizonte- MG - Brazil
(2) Copenhagen University Observatory
   Oster Voldgade 3 - DK 1530 - Copenhagen - Denmark
(3) Copenhagen University Observatory
   Brorfeldeveje 23 - DK 4340 - Tollose - Denmark



References:

Claria, J.J.: 1976, Inf. Bul. Var. Stars, no. 1106
Conti, P.S., Alschuler. W.R.: 1971, Astrophys. J. 170, 325 [BIBCODE 1971ApJ...170..325C ]
Cousins, A.W.J.: 1973, Mon. Notes Astron. Soc. South Africa 32, 11 [BIBCODE 1973MNSSA..32...11C ]
Herbst, W., Miller, D.P., Warner, J.W., Herzog, A.: 1982, Astron. J. 87, 98 [BIBCODE 1982AJ.....87...98H ]
Lafler, J., Kinman, T.D.: 1965, Astrophys. J. Suppl. Ser. 11, 216 [BIBCODE 1965ApJS...11..216L ]
Niemela, V. Morrison, N.D.: 1988, Publ. Astron. Soc. Pacific 100, 1436 [BIBCODE 1988PASP..100.1436N ]