Revisiting V1309 Sco 2008 outburst spectra. Observational evidence for theoretical modeling of stellar mergers

Understand

CONTEXT: V1309 Sco is the only certain noncompact stellar merger, due to its indisputable preoutburst light curve matching that of a contact binary of almost equal mass stars.

• Therefore, anything that can be deduced from the existing observations serves as benchmark constraints for models.
• AIMS: We present some observational evidences to guide future hydrodynamical simulations and common envelope studies.
• METHODS: Using archive spectra taken at high and mid spectral resolution during the V1309 Sco outburst and late decline, together with the inferential methods we developed to study nova ejecta through panchromatic high resolution spectroscopic follow ups, we constrain the physical state, structure, dynamics and geometry of the transient originated in the stellar merger.