UBVJHKLMN PHOTOMETRY AND OPTICAL SPECTROPHOTOMETRY OF THE SYMBIOTIC MIRA V407 CYGNI

The optical and infrared photometric and spectroscopic observations of the symbiotic star V407 Cyg in 1984-1997 are presented. Its cool comp onent is shown to be a Mira variable with a pulsation period P approxi mate to 745(d) and an amplitude Delta K 1(m). While the pulsation peri od may be unstable on a short time scale, its mean value given above h as not changed appreciably over the last 50 years. It is noted that th e intensity of the TiO lambda 6180 and lambda 7100 Angstrom bands and, accordingly, the spectral type of the Mira can be the same for its di fferent (Delta V greater than or equal to 2) brightness. The mean infr ared brightness of V407 Cyg increased during our observations, and, si multaneously, the star became bluer. In 14 years, it brightened in K b y 2 0(m).4. The pulsations and the trend are attributable to variation s in the same parameters of the star: in the luminosity and temperatur e of the Mira, as well as in the optical depth of the dust envelope. T he latter consists of a mixture of fairly large (a(gr), greater than o r equal to 0.08 mu m) silicate and graphite grains. Its optical depth at maximum light of the Mira is tau(J) = 0.25. The mass-loss rate over the last decade was similar to 7 x 10(-7) M. yr(-1), which is more th an one order of magnitude lower than the expected value for a Mira wit h such a long pulsation period. The spectrum of V407 Cyg was first obt ained in August 1994; it appears as a typical symbiotic spectrum with numerous emission lines against the emission from a red giant. During the outburst, the temperature of the hot component was similar to 6 x 10(4), while its bolometric luminosity did not exceed 1% of the maximu m luminosity of the Mira.