Nova Sco 2008 ( =V1309 Sco ) is one of the V838 Mon type eruptions rather than a typical classical nova .
This enigmatic object was recently shown to have resulted from the merger of the two stars in a contact binary .
It is the first stellar merger that was undergoing a common envelope transient .
To understand the properties of its binary progenitor , the pre-outburst light curves were analyzed by using the W-D ( Wilson and Devinney ) method .
The photometric solution of the 2002 light curve shows that it is a deep contact binary ( f = 89.5 ( \pm 40.5 ) \% ) with a mass ratio of 0.094 .
The asymmetry of the light curve is explained by the presence of a dark spot on the more massive component .
The extremely high fill-out factor suggests that the merging of the contact binary is driven by dynamical mass loss from the outer Lagrange point .
However , the analysis of the 2004 light curve indicates that no solutions were obtained even at an extremely low mass ratio of q=0.03 .
This suggests that the common convective envelope of the binary system disappeared and the secondary component has spiraled in the envelope of the primary in 2004 .
Finally , the ejection of the envelope of the primary produced the outburst .