The nature of peculiar red novae with K-M spectra in the outbursts Vitaly Goranskij, SAI, Moscow University in cooperation with Natalia Metlova, SAI Crimean Station, Ukraine; Sergei Shugarov, SAI, Moscow University & Astronomical Institute of Slovak Academy of Sciences; Astronomical Institute of Slovak Academy of Sciences; Peter Kroll, Sonneberg Observatory, Germany; Elena Barsukova, Valentina Klochkova & Azamat Valeev, Special Astrophysical Observatory of Russian Academy of Sciences. Special Astrophysical Observatory of Russian Academy of Sciences. (Munari et al, 2002) Stars that Erupt into Cool Supergiants (SECS) Stars that Erupt into Cool Supergiants (SECS)

Wide system containing a B type star. Explosion of the hot companion up to M V = – 10 m. Cool K0 – M giant in outburst. Mass equal to a few solar masses erupted into space. Very cool oxygen-rich stellar remnant, supergiant of L – M type. Not a classical nova, a sample of a new class of astrophysical objects. What is a red nova? Tycho Brage observes a sudden appearance of a nova star in 1572 (Flammarion textbook, 1902). In the Flammarion’s textbook all the novae were explained as a result of stellar collisions. A term of nova means only a new star unseen earlier.

GCVS editors did not believe that the star might be both a nova and a red supergiant as written in different papers and gave It two names

The photometric history of V838 Mon. I. The 2002 outburst Dust formation L type spectrum out of the V band

Spectrum of V838 Mon in the outburst (SAO RAS 1-m Zeiss telescope) Resembles K0I type star, but the absorption lines are 3-4 times stronger

Spectra of V838 Mon in the different phases of the outburst Pre-maximum Shock wave in the peak of outburst After the peak of outburst

Line profiles of high-resolution spectra V838 Mon in the peak of outburst. BTA/NES spectra (resolution ~1 km/s) first analysed by Kipper et al. (2004) Classical P Cyg profiles: Smooth profiles, ~radially symmetric outflow

The photometric history of V838 Mon. II. Pre- and post - explosion evolution Digital reduction of Sonneberg (Germany) and Sternberg Institute (Moscow, Russia) photographic plates.

V838 Mon progenitor. Photography taken on 1943 February 28 with the 40-cm astrograph of Sonneberg Observatory (Germany). Fragment of HST image Single B3V star V838 Mon, binary of B3V stars

The photometric post-outburst history of V838 Mon. Different filters. Capture and engulf of its B3V companion. Julian Date Julian Date B3V star inside the red supergiant! Radius of the red supergiant it equal to Rsun

Spectral energy distribution V838 Mon before the outburst (progenitor) and after outburst (L type supergiant in 2002). Corrected for reddening of E(B-V)=0.77.

Unreddened spectral energy distributions of V838 Mon components. If we know correct energy distributions of progenitor binary and a surviving B3V companion, we can calculate the energy distribution of exploded star. It was a B3V star, too.

Cluster of B type stars around V838 Mon. Color-Magnitude diagram The location of V838 Mon components on the Afsar & Bond’s CM diagram of the cluster. Both components have the reddening equal to the cluster’s one but are low-luminosity stars.

Flux density Wavelength, Angstrem Post-outburst spectral evolution of V838 Mon Approach & engulf

Photometric history of V4332 Sgr. I. POSS The light curve in the R filter. Brightening before outburst is seen

Photometric history of V4332 Sgr. II. V band light curve V band light curve SAI, 1986

Spectral energy distributions of V4332 Sgr before and after 1994 outburst Reddening of E(B-V)=0.32 is taken into account.

V4332 Sgr spectrum 11 years after outburst V4332 Sgr spectrum 11 years after outburst Resonance lines of Al I, Ca I, Sr I; triplets of Mn I, Cr I; intercombination line of Mg I 4571Å; faint emissions of Rb I; molecular emissions of AlO, TiO, large number of Cr I lines and wide TiO bands of M7 type star with the temperature of 2700К. Emission line spectrum belongs to cool gas nebula. T=1100K. Flux density Wavelength Slit

Comparison of two red novae spectra, V4332 Sgr and V838 Mon in 2007

V838 Mon surroundings and Light echo

Light echo of V838 Mon Compared with X-ray light echo of GRB Our images taken with 1-m Zeiss telescope

First HST image of V838 Mon light echo taken on 2002 April 30 in B band. Arcs and the central gap are seen

Model of light echo Model of light echoObserverBoundary of the dense interstellar medium Light years

Echo expansion in four directions Superluminal part

Computer modeling of surrounding dust nebula Distance = 6 kpc generally accepted Different structures of nebulosity being cut by narrow ellipsoid give the arcs

Distance = 6 kpc Bad approximation of superluminal part

Computer modeling of light echo. II. Distance = 4 kpc.

We assume that V838 Mon components both are young pre main sequence stars in the stage of gravitational contraction, and the ignition of hydrogen in the center of one of them gave a powerful push to star expansion. Later, 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 case why red novae look like cool supergiants. CONCLUSION Not a Thorne – Zitkow like event. No place for a neutron star in the young binary system. Exploding star had zero age main sequence composition (Kipper et al., 2006).

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