The symbiotic recurrent nova V3890 Sgr: binary parameters and pre-outburst activity

We present and analyze optical photometry high resolution SALT spectra of the symbiotic recurrent nova V3890 Sgr at quiescence. The orbital period, P=747.6 days has been derived from both photometric spectroscopic data. Our double-line orbits indicate that mass ratio is q=M_g/M_WD=0.78+/-0.05, component masses are M_WD=1.35+/-0.13 Msun, M_g=1.05+/-0.11 Msun. orbit inclination approximately 67-69 degr. red giant filling (or nearly filling) its Roche lobe, distance set by lobe radius, d=9 kpc, consistent with resulting pulsation period. outburst magnitude then very similar to those RNe in Large Magellanic Cloud. shows remarkable activity between eruptions timescales observed novae T CrB RS Oph Z And-type systems. active source a double-temperature structure which we have associated presence an accretion disc. would be caused changes rate. also provide evidence contains CO WD accreting high, few 1e-8 - 1e-7 Msun/yr, growing mass, should give rise Type Ia supernova within about 1,000,000 yrs expected lifetime giant.