V838 Mon photometry and spectra

This rise is also reflected in the spectra, showing a gradual relative increase in the continuum flux at shorter wavelengths. In addition, a slow brightening of the H{alpha} emission line starting in 2015 was detected. These changes might imply that the B3V companion is slowly reappearing.

During the same time interval, our analysis reveals a considerable change in the observed colours of the object along with a steady decrease in the strength and width of molecular absorption bands in our low-resolution spectra. These changes suggest a rising temperature of the cool supergiant along with a weakening of its wind, most likely combined with a slow recovery of the secondary due to the evaporation of the dust and accretion of the material from the shell in which the hot companion is embedded.

From our medium-resolution spectra, we find that the heliocentric radial velocity of the atomic absorption line of TiI 6556.06{AA} has been stable for more than a decade. We propose that Tii lines are tracing the velocity of the red supergiant in V838 Mon, and not representing the infalling matter as previously stated.