The double outburst of the unique object V 838

We present spectroscopic and photometric observations of the recent peculiar outburst of V838 Mon, carried out at Rozhen and Toru´n observatories. Our data cover a period of three months beginning just before the second eruption. The evolution of the outburst is divided into four phases. The changes of particular spectral features for each of these phases are shortly discussed. V838 Mon is one of the most enigmatic stellar phenomena observed during the last several years. The outburst in the beginning of 2002 January (Brown 2002) with an amplitude in V of at least 5 m pointed to a possible classification of this object as a nova. Its relatively cool K giant type spectrum almost unchanged during the next three weeks (Zwitter & Munari 2002) suggested that it could be an extremely slow nova. Simultaneously, many metal lines showed P Cyg profiles with an outflow velocity of about 200–300 km s −1 , whereas the hydrogen Balmer lines presented emission peaks without P Cyg absorption components. Iijima (2002) suggested that we observed the flare-up phase of a post-AGB star. All these speculations were broken about February 1, when an unexpected second outburst (V amplitude ∼4 m) similar to the first one, occurred. Few days later, on about February 4–5, V838 Mon reached the maximum with almost 6. m 5 in V band. V838 Mon phenomenon has excited numerous observers, amateurs and professional astronomers, which reflected in nearly 30 IAU Circular publications dedicated to this object. Additionally, almost 400 messages has been posted in the amateur VSNET network. Recently, the first scientific paper concerning V838 Mon has been published (Munari et al. 2002). However, there is no idea about the physical mechanism of V838 Mon activity, yet. We observed V838 Mon photometrically in U BV R c I c system using the 60cm Cassegrain telescope at Toru´n Observatory with one-channel diaphragm pho-tometer equipped with a cooled C31034A photomultiplier. The high-resolution (0.2 ˚ A/pix) spectra were collected with the coudé spectrograph fed by the 2m telescope at Rozhen Observatory. Low-resolution spectroscopic observations (2 ˚ A/pix) were carried out at Toru´n Observatory using the Canadian Coper-nicus Spectrograph attached at the Cassegrain focus of the 90cm telescope. All our CCD spectra were processed using the available tasks in the IRAF software package. Part of the Toru´n spectra, obtained in the best weather conditions,