Infrared photometry of Sakurai's object (V4334 Sgr) in 2000

The infrared photometric observations of V4334 Sar in 2000 are presented. T hey show that a gradual, but nonmonotonic increase in the optical depth of its dust envelope, which was formed early in 1997, had continued until the mid-summer. In July 1999 and July 2000, tau (1.25 mum) approximate to 7.7 a nd 11.3, respectively. From July through October 2000, the optical depth de creased appreciably. From October 1998 (the first deep minimum of visual br ightness) until now, the amplitude of the bolometric-magnitude variations i n V4334 Sgr is similar to0.(m)5. The relation between the bolometric and L magnitudes (M-bol, L) can be fitted by a linear function, m(bol) = 1.25L 4.04. In the dust-envelope model chosen, the percentage of large (a(gr) = 0 .2-0.3 mum) dust grains by particle number increased by a factor of similar to4. In the summer of 2000, their fraction by mass was similar to 78%, and they mainly contributed to the optical depth of the dust envelope. No appr eciable correlation between optical depth and bolometric flux was observed. (C) 2001 MAIK "Nauka/Interperiodica".