OBSERVATIONS OF SAKURAIS OBJECT (V4334 SGR) IN 1997 AND ITS EVOLUTIONIN 1996-1997

The photometric UBV and spectroscopic observations of Sakurai's star ( V4334 Sgr) in 1997 are presented. Its mean B and U brightness continue d to decline. The B-V color index systematically increased and reached 1.(m)7 in October 1997. In 1997, the spectrum exhibited intense Swan C-2 molecular bands. The spectral type of the star was estimated to be C1,4 in June and C3,4 in October. The presence of noticeable isotopic Chi and C, molecular bands suggests that Sakurai's star belongs to th e J group of carbon stars. The temperature and bolometric luminosity o f the star were determined. In two years, the star cooled down by abou t 3000 K, while its luminosity rose by more than a factor of 2. The in frared photometric observations show that by June 1997 an optically th ick [tau(V) similar or equal to 1] dust shell condensed around V4334 S gr at a distance of similar to 80R which concealed the actual visual brightening of the star itself. The mass of the dust shell was similar to 1.6 x 10(-8)M., and it contained mostly grains of medium (0.1 mu m ) and large (0.25 mu m) sizes. By September, the shell increased in ma ss by a factor of similar to 1.4 as a result of grain growth, while th e total grain number reduced. The fraction of large grains reached 80% by mass, Over the same period, the bolometric flux from the star rose by 20%. The evolutionary track of V4333 Sgr was constructed in the lo g T-eff, M-bol diagram and compared with that of FG Sge.