ИСТИНА

V838 Mon is a representative of a new class of astrophysical objects, red novae, which is known since 1988. In outbursts, these stars turn out into red supergiants and don’t pass a nebular stage. In the explosion of a red nova, the matter of a few solar masses is erupted into space. We report the results of UBVRI photometry, medium resolution spectroscopy of V838 Mon along with archive photographic photometry of its progenitor. Spectral analysis during the outburst showed that V838 Mon was the star having nearly solar abundances. We determined the spectral energy distribution of bouth progenitor’s components in the wide range of wavelengths between 4400 –7900A (BVRI bands). By comparing of energy distributions before and after the outburst, it was established that a progenitor of the nova was a binary system containing hot B3V type stars. The star exploded in 2002 was 1.36 +/-0.03 times brighter than its companion, and it mimicked with its companion having the same color indices. V838 Mon belongs to a sparsely populated cluster of B stars (Afsar & Bond, 2007). We found that both components of the progenitor were underluminous objects for their spectral class. Our post-outburst photometry and spectroscopy shows approach of B3V companion with the expanding cool supergiant, the remnant of the outburst. A photometric eclipse of B3V component was discovered on December 2006. We explained the eclipse 2006 by a forming of a temporary briefly living accretion disc around the hot component. Using the brightness of the hot component lost in the eclipse, we defined a full spectral energy distribution of the exploded component before the outburst in the BVRI bands. After the eclipse which was lasting 70 days we observed a sharp weakening of V838 Mon brightness in short U and B bands. Probably this weakening connects with an entering of B3V component into opaque layers of the cool star and with an absolute disappearance of this component radiation, and also the emission gas spectrum, which excited by this hot star, disappeared. The photometry showed that the cool component temperature has increased until 2200 K in October 2008. Finally, hot B3V companion plunged under photosphere of cool remnant in the Autumn 2008. Now it is invisible in the spectra and the energy distribution. We investigated the light echo and established that V838 Mon is plunged into gas-dust nebula the light echo was extending through which. V838 Mon is situated near a centre of this nebula. A distance of 5 +/- 1 kpc defined by ours according to light echo corresponds to the distance defined by normal B stars of the cluster. The nature of peculiar red novae was not predicted of the star evolution theory. There are some observation indications for a young age of red novae. We are based on this assumed that V838 Mon components are pre main sequence stars in the stage of gravitational contraction, and the ignition of hydrogen in the centre of one of them gave a powerful push to star expansion. When the radiation of the internal burning and shock waves reached the surface, its area became so large that could not be heated up to high temperature. This may be the cause why red novae look like cool supergiants.