摘要：Context. One very important object for understanding the nature of red
novae is V1309 Sco. Its pre-outburst observations showed that, before its red-nova
eruption in 2008, it was a contact binary quickly evolving to the merger of the
components. It thus provided us with a direct evidence that the red novae result from
stellar mergers.
Aims. We will study the evolution of the post-merger remnant of V1309
Sco over time.
Methods. We analyse the spectral energy distribution (SED) of the object
and its evolution with time. From various optical and infrared surveys and observing
programmes carried out with OGLE, HST, VVV, Gemini South, WISE, Spitzer,
and Herschel we constructed observed SED in 2010 and 2012. Some limited
data are also available for the red-nova progenitor in 2007. We analyse the data with our
model of a dusty envelope surrounding a central star.
Results. Dust was present in the pre-outburst state of V1309 Sco. Its
high temperature (900–1000 K) suggests that this was a freshly formed dust in a presumable
mass-loss from the spiralling-in binary. Shortly after its 2008 eruption, V1309 Sco became
almost completely embedded in dust. The parameters (temperature, dimensions) of the dusty
envelope in 2010 and 2012 evidence that we then observed matter lost by the object during
the 2008 outburst. Its mass is at least 10-3M⊙. The object remains
quite luminous, although since its maximum brightness in September 2008, it has faded in
luminosity by a factor of ~50
(in 2012). Far infrared data from Herschel reveal presence of a cold
(~30 K) dust at a distance
of a few thousand AU from the object.
Conclusions. Similarly to other red novae, V1309 Sco formed a
slowly-expanding, dense, and optically-thick dusty envelope during its 2008 outburst. The
main remnant is thus hidden for us. Far infrared data suggests that the object passed an
episode of intense mass loss in its recent history. This conclusion could be verified by
submillimeter interferometric observations.
