Nova Monocerotis 2002 (V838 Mon) at early outburst stages

We obtained UBVR photometric and spectroscopic observations during the outburst of V838 Mon. Before its outburst, the B brightness of the star had been stable (similar to15.(m)85) for 45 years. This was a blue star with the color index (B-V)(0) = -0.(m)03 +/- 0.(m)1 and may have been a cataclysmic variable. In the middle of March 2002, the outburst amplitude reached 8.(m)1 in B. The star has the counterpart V1006/7 in M 31 in luminosity at maximum and in spectrum. The unusual spectrum at the premaximum stage originated in the expanding photosphere of a cool K-type giant. The expansion velocity of the photosphere was 150 km s(-1); the maximum velocity in the expanding stellar envelope reached 500 km s(-1). The absorption components of neutral metal lines were enhanced by a factor of 3 or 4 compared to a normal K-type star. No overabundance of s-process elements was found. One day before the brightness peak, an intense Ha emission line with broad wings, FWZI = 3100 km s(-1), and numerous lines of ionized metals appeared in V838 Mon, which is characteristic of normal classical novae. We show light, color, and spectral variations of the object. (C) 2002 MAIK "Nauka/Interperiodica".